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Construction Materials Manual Which building material is suitable for which purpose? Which ceramic finishes represent the best solutions for walls, which for floors? Can a composite floor slab span a greater distance than a reinforced concrete floor slab with the same depth? Is it sensible to lay a sisal carpet in the entrance zone or would a velour one be better? Or neither of these? How does one go about developing a "new" building material up to the point of its use in a structure? The list of questions in the construction process is a long one - and the answers can be found here in the Construction Materials Manual. In addition, 25 examples of international projects illustrate the aesthetic, sometimes traditional, sometimes innovative, uses of the materials explained in detail in the main body of this new work of reference. This, the latest in the series of Birkhauser Construction Manuals, deals with the following: •

the boundary conditions and the significance of the choice of materials for architecture and building

•

the influence of the material - application, design, aesthetics

•

detailed information on the properties and applications of building materials

•

a unique compendium of sustainability parameters for individual building materials and forms of construction

•

a list of standards, directives and statutory instruments relevant in Europe

•

the effects of building materials, forms of construction and architectural designs in the context of case studies, including large-scale details

Part A: Materials and architecture Part B: Properties of building materials Part C: Applications of building materials Part D: Case studies in detail Part E: Appendix

This book was compiled at the Chair of Design and Energy-Efficient Building, Prof. Manfred Hegger Department of Architecture, TU Darmstadt www.architektur.tu-darmstadt.de/ee In conjunction with Institut fUr internationale Architektur­ Dokumentation GmbH & Co. KG, Munich www.detail.de

Birkhauser - Publishers for Architecture Basel . Boston· Berlin Edition Detail Munich

e

ons rue Ion e

a erla 5 anua HEGGER AUCH-SCHWELK FUCHS ROSENKRANZ

. .

BIRKHAUSER - PUBLISHERS FOR ARCHITECTURE BASEL . BOSTON · BERLIN EDITION DETAIL MUNICH

This book was compiled at the Chair of Energy-Efficient Building Design, Prof. Manfred Hegger Department of Architecture, TU Darmstadt www.architektur.tu-darmstadt.de/ee in conjunction with Institut fUr internationale Architektur-Dokumentation GmbH & Co. KG, Munich www.detail.de

Authors

Specialist articles:

Manfred Hegger

Christian Schittich, Dipl.-Ing. Architect

Prof. Dipl.-Ing. M. Econ Architect

Institut fUr internationale Architektur-Dokumentation, Munich

Chair of Energy-Efficient Building Design, TU Darmstadt Christiane Sauer, Dipl.-Ing. Architect Volker Auch-Schwelk

Formade/Architektur

+

Material, Berlin

Dipl.-Ing. Architect Chair of Design and Building Studies, TU Darmstadt

Peter Steiger, Prof. Architect intep AG, Zurich

Matthias Fuchs Dipl.-Ing. Architect

Alexander Rudolphi, Dipl.-Ing.

Chair of Energy-Efficient Building Design, TU Darmstadt

GFOB Berlin mbH, Berlin

Thorsten Rosenkranz

Dirk Funhoff, Dr. rer. nat.

Dipl.-Ing.

BASF, Ludwigshafen

Chair of Energy-Efficient Building Design, TU Darmstadt Marc Esslinger Scientific assistants:

frog design gmbh, Herrenberg

Jurgen Volkwein, Dipl.-Ing. Architect (Building services) Martin Zeumer, Dipl.-Ing. (Glass, Physical parameters of materials,

Karsten Tichelmann, Prof. Dipl.-Ing.

Life cycle assessments)

Patrik Jakob, Dipl.-Ing. VHT, Darmstadt

Student assistants: Christoph Drebes, Andreas Gottschling, Cornelia Herhaus,

A CIP catalogue record for this book is available from the Library of

Viola John, Yi Zhang

Congress, Washington, D.C., USA

Editorial services

Die Deutsche Bibliothek lists this publication in the Deutsche National­

Editors:

http://dnb.ddb.de.

Bibliographic information published by Die Deutsche Bibliothek. bibliografie; detailed bibliographic data is available on the Internet at Steffi Lenzen, Dipl.clng. Architect (project manager) Julia Liese, Dipl.-Ing.

This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the right of translation,

Editorial assistants:

reprinting, re-use of illustrations, recitation, broadcasting, reproduction on

Carola Jacob-Ritz, M. A.; Sabine Schmid, Dipl.-Ing.;

microfilms or in other ways, and storage in databases. For any kind of use,

Manuel Zoller, Dipl.-Ing.

permission of the copyright owner must be obtained.

Drawings:

This book is also available in a German language edition

Marion Griese, Dipl.-Ing.

(ISBN 3-7643-7272-9).

Drawing assistants:

Editor:

Kathrin Draeger, Dipl.-Ing.; Norbert Graeser, Dipl.-Ing.;

Institut fUr internationale Architektur-Dokumentation

Emese K6szegi, Dipl.-Ing.; Nicola Kollmann, Dipl.-Ing.;

GmbH & Co. KG, Munich

Elisabeth Krammer, Dipl.-Ing.; Andrea Saiko, Dipl.-Ing.

www.detail.de

Production / DTP:

©

Roswitha Siegler

Birkhauser - Publishers for Architecture, P.O. Box 133, 4010 Basel,

2006 English translation of the 1st German edition

Switzerland, Part of the Springer Science+Business Media. Reproduction:

www.birkhauser.ch

Martin Hartel OHG, Martinsried Printed on acid-free paper produced from chlorine-free pulp. TCF Translation into English:

00

Printed in Germany

Gerd H. S6ffker and Philip Thrift, Hannover Hardcover:

Softcover:

ISBN-1O: 3-7643-7570-1

ISBN-1O: 3-7643-7571-x

ISBN-13: 978-3-7643-7570-6

ISBN-13: 978-3-7643-7571-3

Contents

Preface

Part A

6

Materials and architecture

9

Part C

Applications of building

102

materials The surface in contemporary

2

3

10

architecture

1

The building envelope

Christian Schittich

2

Insulating and sealing

132

3

Building services

146

materials scout

4

Walls

152

Christiane Sauer

5

Intermediate floors

162

6

Floors

170

7

Surfaces and coatings

186

The architect as building

The critical path to sustainable

14

18

construction

104

Peter Steiger 4

Criteria for the selection of

22

building materials Alexander Rudolphi 5

The development of innovative

28

Part D

Case studies in detail

202

materials Dirk Funhoff 6

Touching the senses - materials

Project examples 1 to 25

204-263

32

and haptics in the design process Marc Esslinger

37

Part E

Stone

38

materials

2

Loam

44

Karsten Tichelmann, Patrik Jakob

3

Ceramic materials

48

Glossary: Hazardous substances

4

Building materials with mineral

54

Alexander Rudolphi

5

Bituminous materials

62

Statutory instruments, directives,

6

Wood and wood-based products

66

standards

7

Metal

76

Bibliography

8

Glass

84

Picture credits

275

9

Synthetic materials

90

Subject index

277

Life cycle assessments

98

Index of names

279

Part B

Properties of building

Appendix

materials Glossary: Physical parameters of

264

268

binders

10

270 272

5

Preface

Books explaining the fundamentals of building

The Construction Materials Manual combines

materials have long since been standard read­

the contents of these three formats. It brings

ing for architects and engineers. They supply

together clearly the technical, sensual and, for

comprehensive information about materials for

the first time, also the ecological aspects in one

construction, explain their origins and produc­

work. Therefore, continuing in the tradition of

tion processes, outline the forms in which they

the series of the Construction Manuals, it closes

are available and the potential applications,

a sensitive gap. The reader gains access to a

and hence provide an in-depth understanding

more comprehensive treatment of building

of properties and processing options. The

materials. Based on this approach, the choice

publications currently available also follow the

of material can be made with more circum­

traditional layout: an overview divided into sec­

spection and care, will also permit more sound

tions devoted to the groups of materials, with

reasoning than was possible in the past. The

comprehensive information on how they affect

carefully prepared, comprehensive parameters

the performance of the building.

now enable verifiable statements instead of

This established technical and business-like

efficiency and sustainability in the building sec­

vague claims, especially in the categories of approach has been supplemented recently by

tor. This also means we can say farewell to glo­

other groups of publications. One group is the

bal prejudices regarding building materials;

books - some of them in large format - of sam­

there is actually no building material that can

ples of materials which with their primarily visu­

be unanimously recommended or rejected

al means of communication would seem to

without any riders.

represent the antithesis to the aforementioned standard works. They present extensive rang­

Does this mean that "anything goes" where

es of materials or provide an insight into the

building is concerned? No, it always depends

diversity of the possibilities of individual

on the structural, building performance, func­

groups of materials. They display the available

tional and environmental contexts and the

diversity as materials or in as-built contexts.

extent to which the material is used. The

This illustrates the increasing need to place

Construction Materials Manual can be used to

the way we experience building materials on a

check the intended application, to establish

sensual level at the very heart of our decisions

whether the planned material should be con­

regarding materials and hence improve the

sidered as suitable or critical. Unfavourable

tangible qualities of the built environment in

results need not necessarily lead to the exclu­

visual and sensual terms. The task of such

sion of a material preferred for economic or

books is to show us the surface of the material.

design reasons. Increasingly, we find that

The other group is those recent publications

material properties can be influenced, in the

and sets of figures that primarily consider how

sense of "custom-made". In the future archi­

building materials affect the environment and

tects, designers and engineers - also with the

our health, also their durability and recyclabili­

help of the knowledge gathered together in this

ty plus other sustainability criteria. These

book - will be able to specify desired proper­

parameters were neglected for many years

ties and assist in the development of new, high­

although the building industry consumes the

ly efficient materials. At the same time, they can

largest share of all raw materials and energy

therefore make a significant contribution to

and - despite the comparative longevity of this

improving the quality of building and to extend­

industry's products - also contributes the lion's

ing the design repertoire.

share of the waste produced. The origins of the impact of building operations can be traced

6

The choice of material has a very decisive

back to, above all, the choice of materials.

effect on the appearance and perception of

Until now, their criteria and indicators have

buildings, and not only their surfaces. For hun­

only been available to a specialist circle of

dreds of years the materials available for build­

readers.

ings were very limited. Knowledge about mate-

rials was acquired over generations and hand­

only in design, is clarified. This aspect is still

criteria. Various typical, layer-type construc­

ed down. Today, the expanding world of mate­

much underestimated in architecture.

tions, presented in tabular form, are compared

disposal for creating architecture. The risks of

Part B "Properties of building materials" is dedi­

mental effects and durability aspects related to particular components can be read off directly,

rials puts a broad selection of materials at our

at the end of each section. From this, environ­

using new materials are high because long­

cated to the overall consideration of the materi­

term experience is not available. Nevertheless,

als themselves. Here, the materials are sorted

which enable designers to estimate the overall

the playful use of and pleasure in experiment­

into groups according to their origins and pro­

impact on the environment of components and

ing with materials are increasingly evident in

duction, methods of processing, but also their

the complete structure at an early planning

our architecture. Material diversification, materi­

chemical composition, physical properties plus

stage. Again in this section, the form of presen­

al alienation, conscious misuse of materials or

their impact and appearance. This section

tation is based on the need to provide the infor­

materials "borrowed" from other industries have

reviews the fundamentals for using the building

mation in a compact format, and therefore uses

become acknowledged styling tools. Besides

materials covered and mentions the risks of

the preferred method of conveying information

the primary edict of architectural form, the rhet­

those materials. The properties in terms of

for architects, i.e. photographs, drawings and

oric of the materials is increasingly becoming

building performance are mainly shown in the

graphics.

the focal point of the culture of our built envi­

form of tables. Wherever possible, the text is

ronment. Diverse innovations are creating an

backed up with drawings, photographs and

incredible need for information among archi­

diagrams. Environmental parameters for the

Part D "Case studies in detail" was to present

tects and engineers.

materials are described at the end of this sec­

the relationship between architectural expres­

The prime aim of the selection of buildings in

tion and are summarised in practical terms for

sion and the materials used. The majority of

The Construction Materials Manual cannot pre­

the main building materials. Common reference

buildings represent recent projects that are

sent every material, track every trend. Never­

units such as m2 or kg are employed for easy

notable for their use of surface textures limited

theless, the authors have tried to take into

comparison and ease of understanding.

to just a few materials. The presentation of the

tects today by covering a wide range of groups

Just considering the material alone is always

cal details for the use of such materials. The

account the diverse options available to archi­

projects features the materials and shows typi­

of materials, by describing their use in various

an abstract exercise for planning and design

intention is to illustrate the architectural

practical contexts and by direct comparisons

when materials have a wide range of potential

strengths that can evolve from an economic

of their properties. For unconventional groups

applications. This is true for the majority of

and skilful choice of materials.

of materials, the various levels of consideration

building materials. For example: metals are just

can perhaps to some degree compensate for

as useful as structural components as they are

the features that characterise our traditional

as cladding to external walls or linings to sof­

department and all the institutions and people

building materials: dependable awareness of

fits, or pipework, or facade members. The

who contributed to this publication, and those

their properties, familiarity with their treatment

authors therefore also saw it as part of their

who so generously provided material for inclu­

and use.

task to show the unison between material and

sion.

Finally, I should like to thank all the staff of my

design in addition to the wide range of potential The layout of the book follows the procedure for

materials. This context made it necessary to

Damstadt, August 2005

choosing building materials and then integrat­

formulate the different possibilities and relation­

Manfred Hegger

ing them into the draft and detail designs.

ships that result from specific applications.

Part A "Material and architecture" approaches

Accordingly, Part C "Applications of building

the current and fundamental aspects of choice

materials" describes assemblies of compo­

of materials. The articles show how choice of

nents with respect to the use of the material.

material influences contemporary architecture

Besides functional and constructional aspects,

and trace the associated selection processes.

building performance criteria such as fire pro­

They present the importance of sustainability

tection, thermal insulation and sound insulation

criteria in the choice of material and describe

are considered specifically for the particular

the dynamics in the development of innovative

application (e.g. building envelope, intermedi­

building materials. Furthermore, the enormous

ate floors). The multitude of design options and

part played by the surfaces of materials as the

their framework conditions is derived directly

interface between building and occupants, not

from this. This also applies to the sustainability

7

Part A

Materials and architecture

The surface in contemporary architecture Christian Schittich

Fig. A

Limestone stairs worn by tho usands of feet over h undreds of years, Chapter Ho use, Wells Cathe­ dral, UK, com menced c. 1 1 80 (stairs date from c. 1 255), Adam Lock et al.

2

The architect as building materials scout Christiane Sauer

3

The critical path to sustainable construction Peter Steiger

4

Criteria for the selection of building materials Alexander Rudolphi

5

The development of innovative materials D irk Funhoff

6

Touching the senses - materials and haptics in the design process Marc Esslinger

The surface in contemporary architecture Christian Schittich

The increasing overabundance of stim u l i , sen­ sual impressions and colourful images has embraced architecture as well , even though the reaction to this is mixed . Some architects adapt to the c ircumstances and respond with simi larly colourful images silk-screen-printed on brittle g lass. Or with multi-coloured patterns over large areas, flickering media facades and i l luminated screens. But others contemplate the quality of tried-and-tested build ing materials soli d , jointed natural stone, fair-face concrete, untreated timber or clay brickwork - in order to demonstrate the physical presence of a struc­ ture in an i ncreasingly virtual world, or as a deliberate contrast to shrill surroundings. What­ ever approach the architect chooses, the sur­ face always plays a dominant role. It is essen­ tially through the surfaces we see and touch that we perceive architecture. Their colours, textures and auras dominate the characters of interiors and facades. Since time immemorial, people in all cu ltures have paid special attention to the surfaces of their houses and rooms , have fashioned them and decorated them . We see this in the colour­ fu l tapestries hanging in the tents of nomads, the colourful paintings in churches and palac­ es, and the tiles and stucco work of I slamic architecture (fig . A 1 . 1 ) . I n contemporary archi­ tecture we witness an alternation between schools that place form in the foreground, and others that emphasise the building envelope. Emphasising the surface is currently "in". This goes hand in hand with the increasing separa­ tion between loadbearing structure and build­ ing envelope, but also with new technical options such as printing on glass and plastics, or the reproduction of patterns by means of computer techniques. And, of course, this trend is also l inked to the growing significance of d ifferent media, which seem to imply that the image of a building is sometimes more impor­ tant than the b u i l d i ng itself! However, empha­ sising the surface directs our attention to the material itself, which more and more is being given the proper setting. The material becomes visi ble at its surface and its specific properties dominate its appearance, which depends q u ite decisively on whether a traditional or an indus­ trially fabricated building material is being used, whether the material has been left untreated or covered or coated (to protect against corrosion) , whether it is glossy or matt, textured or plain, or whether its appearance and its properties change over the course of time (intended or unintended) . Like timber, which takes on a si lvery grey colour, or metals, which oxidise and become d u l l , or untreated sandstone, which turns black over time. I n contrast to earlier times when everyday building projects could only make use of the materials available locally, we have at our d is­ posal today an unprecedented d iversity of building materials from the four corners of the globe to which industry i s constantly adding new developments. This d iversity brings with it

10

A 1.1

previously unforeseen opportunities, but also risks, at least in terms of the huge choice. Moreover, the g rowing "staging" of the material, which is not limited to traditional building mate­ rials, leads to more and more products from other sectors of industry - which hitherto found no use in building - being employed in archi­ tecture. "Authentic" materials

The conscious treatment of materials is not a new concept confined to contemporary archi­ tecture. For more than 20 years, Tadao Ando has been using "authentic building materials with substance", such as untreated timber or (inspired by Le Corbusier and Louis Kahn) the raw power of fair-face concrete, in order to create rooms and moods. I n his best designs the surfaces are not absolutely flat, but instead exhi bit a minimal waviness within each form­ work panel; the ensuing play of light and shad­ ow lends the surface an adroit vigorousness (fig . A 1 4) . The buildings of Tadao Ando helped fair-face concrete to make a comeback. However, it was mostly the completely smooth surfaces divided into strict patterns by the formwork panels and punctuated by a regular network of real, some­ times even dummy, formwork tie holes on his ever larger works that found imitators world­ wide. Concrete in all its forms is currently popular. The use of rough formwork boards or subse­ quent furrowin g or bush hammering gives it a striking, coarse character, the addition of col­ oured pigments or certain aggregates lend it a certain materiality. Jacques Herzog & Pierre de Meuron, for example, specified a concrete mix with gravel containing soil plus subsequent coarse pOinting for the external walls of their so-called Schaulager in Basel (2003) in order to achieve a loam-type character (see p. 1 1 2, fig. C 1 .27 c). On the other hand, the Basel­ based architectural practice of Morger Oegelo Kerez used a concrete mix with green and black basalt river aggregates plus extensive grinding and polishing on the art gallery in Lichtenstein (2000) to create the appearance of marble (see p. 1 1 2 , fig . C 1 .27 d).

The surface in contemporary architecture

A 1 .1

Gla zed ceram ic tiles and stucco work , Alhambra, Granada, Spai n , 1 4th cent ury A 1 .2 National libra ry o f France, Paris, France, 1 996, Dominique Perra ult with Ga elle Lauriot Pr evost A 1 .3 Thermal baths, Vals, Switzerland, 1 996, Peter Zumthor A 1 .4 S unday school , I baraki , Japan , 1 999, Tadao Ando

A 1 .2

"Genuine" natural stone is used these days almost exclusively on the surface, in the form of thin cladding panels or even as "veneers" just a few millimetres thick bonded to an aluminium backing panel . Countless facades and foyers for banks and insurance companies bear wit­ ness to this. But Peter Zumthor - like Tadao Ando a maestro in terms of the handling of materials - is not satisfied with such approaches. His structures draw their impressive strength from the con­ scious use of a limited number of primarily untreated materials such as stone, timber or concrete. Zumthor wants to expose the "actual nature of these materials, freed from all cultur­ ally mediated mean ing", to allow the "materials to resound and radiate in the architecture". [ 1 ] In works like his stone-clad thermal baths in Vals ( 1 996) or the chapel in Sumvitg covered in larch shingles ( 1 988) , his choice of materials reflects local traditions and helps to establish the structures in their surroundings. For exam­ ple, the thermal baths in Vals takes on the appearance of a monolith growing out of the mountainous landscape, with the stone itself in the form of solid walls made from local quartzite or as floor finishes and the linings to pools made from the same material - providing a multitude of aesthetic and haptic experiences both internally and externally.

overlapping cladding of acid-etched g lass panes (see p. 86, fig . B 8.8) , which thereby impressively reveals the physical presence of this "invisible" material. Translucent but not transparent, the consistent envelope changes its appearance depending on viewing angle, time of day and l i g hting conditions. On their hospital pharmacy in Basel ( 1 999) , Jacques Herzog & P ierre de Meuron achieved a dematerial isation of the building fabric by using silk-screen-printed glass (see p. 1 1 7 , f i g . C 1 .36 c ) . I n t h i s example a completely reg­ ular pattern of green dots was applied to the glass cladd ing which encloses the entire build­ ing, even extending into the window reveals. The clad d i n g therefore changes its appear-

A 1 .3

ance accord ing to the observer's d istance from the building. From far away the building takes on a uniform green appearance, but from clos­ er the green dots become apparent. The spac­ ing of the dots is such that the insulation behind and its fixings remain visible. As the observer changes his or her position, so he or she is treated to unceasing optical interference phenomena which animate the structure and break down its strict contours. The reflections of the surrounding trees merge with the facade. The Austrian architects Andreas Lichtblau and Susanna Wagner also used glass on their par­ ish centre (200 1 ) in Podersdorf on Neusiedler Lake, but this time for a subtle form of decora­ tion. An enclosing and integrating glass wall

Industrially fabricated materials

Glass and transparent synthetic materials, but also metal meshes and fabrics, enable archi­ tects to play with the surface in a special way, to separate the physical and visual boundaries. In this respect, it is especially chal leng i n g to sound out the multifaceted zone between transparency and translucency. That can be achieved by coverin g the g lass with louvres or perforated sheet metal , by printing, by acid­ etching or the specific use of m irror effects and reflections. The individual characters of and contrast between two very different materials - concrete and glass - was turned into an imposing theme by Peter Zumthor on his art gallery in Bregenz (1997) . The monolithic core of in situ fair-face concrete walls and floors is enclosed in an A 1 .4 11

The surface in contemporary architecture

position, the material generates constantly changing colour effects. I nside the building, the interaction with the i nner leaf of translucent g lass results in a pleasant, softly coloured light which generates a positive atmosphere and suits the dance and practice rooms admirably.

IJIJ JJ JJ 1J

JJ

JJ A 1.5

A 1.6

placed in front of the group of buildings was printed with passages of text written by local children mixed with q uotes from the Bible (see p. 1 1 7 , fig. C 1 .36 d ) . The result is not only interesting lighting effects on the buildings behind, but also a type of media facade con­ veying a message. Printing with texts or images - the primary objective of which is an aesthetic effect - still remains the customary form of media facade because active building envelopes with moving i mages and changing messages - with the exception of large advertising screens in city centres - have not yet become a fam i l iar addition to the streetscape despite promising starts. Matthias Sauerbruch and Louisa Hutton also exploited the possibilities of printed g lass for their combined police and fire station in Berlin (see Example 24, pp. 258-60) . I n contrast to the two examples described above, however,

transparency was less i mportant than the con­ cept of large-scale coloured patterns, with reflections in the glass surfaces providing addi­ tional charm. Jacques Herzog & Pierre de Meuron managed to achieve a successful setting for synthetic materials, currently so popular in architecture, on the Laban Centre in south-east London (2003). The plastic four-wall panels are used so skilfully here that the result is a splendid , shim­ mering sculpture (fi g . A 1 .7 ) . It emulates the straight lines of its surroundings, but at the same time its outlines become blurred with the sky, which leads to an almost unrealistic, seem­ ingly intangible appearance. Colours are used very subtly here, with colour applied to the rear faces of only some of the plastic panels. This reinforces the shimmering, pastel-like effect. Depending on lighting conditions and viewing

Synthetic materials in the form of corrugated sheetin g or multi-wall panels are inexpensive products that have been used in building for many decades, but usually for ancillary areas. In architecture they led a sort of shadowy exist­ ence - similarly to plywood, expanded metal or fibre-cement sheeting - until their aesthetic qual ities were discovered and literally brought to the surface - to the visible sides of claddings and linings - in the course of the new aware­ ness of materials. Forming a contrast to this is the stainless steel fabric used by Dominique Perrault for the first time on the National Library of France in Paris ( 1 995) - an example of the sensible transfer of a material from industry (where, for example, it is used for sieves) to architecture. I nternally, in lecture theatres, staircases and other public areas, this semi-transparent material can be used as an acoustically effective soffit and wall lining, to conceal building services, as translu­ cent partitions or as sunshadi n g . This textured light- and air-permeable second skin lends the interior a special qual ity (fig . A 1 .2). Nowadays, the material appears in all sorts of places - from bank foyers to airport car parks. It is an effective treatment for facades too, as the curving skin of stainless steel fabric on the NOX arts centre in Lille demonstrates (see Example 1 5, pp. 234-36) . The facade changes

A 1.7 12

The surface in contemporary architecture

its appearance depending on weather condi­ tions and time of day - sometimes shining in the sunlight and concealing what lies behind it, at other times looking l i ke a semi-transparent, fine veil draped in front of the buildi n g .

MVRDV team, the veil of water flowin g across the outer skin was used to provide texture, its movement leading to a multitude of kaleido­ scope-type patterns and a neverend ing alter­ nation between transparency and translucency.

Variable surfaces

Interior surfaces

The effect and aura of a surface is essentially determined by the properties of the material, by the interaction of d ifferent building materials, by the alternation between closed and open zones, or even by movable elements. Variable building envelopes are not a new phenomenon. The window shutters of earlier times fall into this category of variability, likewise fabric sunblinds; in addition to being functional, they have always served as design features too. But hardly ever before has the aesthetic effect of the variable facade been given so much attention, the con­ trast between the closed and open conditions of hinged or sliding shutters placed in the set­ tings conceived for them today. This applies to the student accommodation in Coimbra, Portu­ gal, (1999) by Manuel and Francisco Rocha de Aires Mateus, where a completely flat, homo­ geneous surface of timber panels becomes an interestingly subd ivided external wall by open­ ing the shutters (figs A 1 .5 and A 1 .6) . Another example is the straig htforward, box-l ike stone house by MADA (see Example 5, pp. 2 1 2- 1 3 ) , whose hinged a n d s l i d i n g shutters d o m u c h to soften the building's severity.

Besides the internal spaces themselves, the materials used i nternally for walls, floors, soffits, furnishings and fittings play a vital role. Their surfaces, textures and colours have a very decisive i nfluence on the atmosphere. Unlike the facade, the building occupants have direct contact with the materials used i nternal ly; they can inspect them close-up, touch them, stroke them , perhaps even smell them. Natural and earthy materials such as timber, stone and con­ crete rad iate warmth, exhi bit a sensual materi­ al ity, whereas synthetic and coated materials can be readily used to express formal design concepts. For instance, i n the minimal ist interior of John Pawson ( 1 999) it is wood with its red­ dish colouring and grain that dominates the character of the room, whereas in the fashion boutique by propeller z (2000) in Vienna it is the curving contours and the rich yel low colour­ ing (figs A 1 .8 and A 1 .9) .

That surfaces need not always be rigid was demonstrated by the Dutch pav i l ion at EXPO 2000 in Hannover, admittedly an extreme example. In this pavilion designed by the

A 1 .8

separates sensible innovation from hackneyed effects simply striving for attention. Focusing increasingly on the surface brings with it the risk of superficiality, which is particularly true for the applied ornamentation so popular at the moment, although it is true that the boundary between tasteful ly applied patterns and pure decoration is of course not fixed . References:

[1 1

Whether plastics, glass or wood, variable or minimalist, brightly coloured or plain, with its vast palette of poss i b i l ities the theme of the sur­ face is probably more excitin g now than it has ever been in the past. A tremendous delight i n experimentation can b e seen everywhere; boundaries are sounded out, trad itional looks q uestioned, new materials and concepts tried out. But sometimes only a narrow dividing line

Zumthor, Peter: Thinking Architect ure. Basel / Boston /Berlin 2006

A 1. 5-6 St udent accommodation, Coimbra , Portugal, 2000, Manuel and Francisco Rocha de Aires Mate us A 1. 7 Laban Centre, London, UK, 2003, Jac ques Herzog & Pierre de Meuron A 1 .8 Private ho use, London, UK , 1ggg, John Pawson A 1.9 Fashion bouti que, Vienna, A ustria, 2000, propeller z

13

The architect as building materials scout Christiane Sauer

A 2. 1

A 2.2

Architects have always tried t o exploit the full design potential of the materials available to them. I n the past, the architectural options were often l i m ited to local materials and traditional methods of working. But over recent decades the g lobalisation of trade plus g lobal communi­ cations and transport logistics networks have changed the situation drastically. For the archi­ tect, the search for the "perfect" material has become the search for the proverbial pin in the - now g lobal - haystack. Research into i nnova­ tive materials generally follows two principles: either the d iscovery of new technologies or the transfer of existing materials to other contexts. Another approach is the targeted new develop­ ment of a material for a certain purpose or application, but this presumes an appropriate budget and a corresponding timeframe.

cone foam with pores just 0.2 x 1 0.6 mm in d iameter. The pores are therefore smaller than the wavelength of solar radiation and smaller than the mean free path of air molecules, which means that the thermal conduction is less than that of stationary air. It was only just a few years ago - in other words nearly 50 years later - that the material was d iscovered for the building sector, and the first products are now appear­ ing on the market i n the form of translucent thermal insulation panels (fig. A 2.2) .

Materials and research

The laboratories and think-tanks of the automo­ tive and aerospace industries are now the world leaders in the development of innovative materials. The ultra-tearproof, highly insulating, extra-lightweight materials and coatings devel­ oped by these centres of excellence also offer new opportunities for sophisticated building concepts. However, it is not unusual for many years to pass before the development of a hi ghly specialised material in a high-tech industry is transformed into a marketable build­ ing product. This may be because the potential of the innovation transfer is not recognised immed iately or because the funding for pro­ tracted , expensive approval procedures is not forthcoming. We therefore get the paradoxical situation of a solution being available before the problem has even materialised: industry already has a high-quality material waiting in the wings, but a use in construction has yet to be found.

A 2.1 A 2.2 A 2.3 A 2.4 A 2.5

14

Aerogel - "Solid Smoke" Light-permeable thermal insulation panel, filled with nanogel "HeatSeats ", Jurgen Mayer H. Thermosensitive bed l in en, J urgen Mayer H. "was 8" heat exchanger station, Utrecht, Nether­ lands, 1998, N L Architects

One example of this dilemma is the nanomate­ rial aerogel, which was developed by NASA way back in the 1 950s as an i nsulating material (fig . A 2 . 1 ) . Aerogel, also called "sol id smoke", has the lowest density of any solid material d is­ covered or developed so far and exhibits excellent insulatin g properties. It consists of 99.8% air; the remaining 0.2% is ultra-fine sili-

Materials and architecture

The adaptation of materials for new applica­ tions is a theme for the architectural avant­ garde , at least since the 1 970s when Frank Gehry built and clad his house in Santa Monica with materials like wire mesh, corrugated sheet metal and plywood. Polycarbonate double- and multi-wall sheetin g and neon tubes from the local DIY store were given a new honour by Rem Koolhaas in the design for the Rotterdam art gallery in 1 992. Transferring the materials into an unusual programmatic context fasci­ nated the architects because it tapped new aesthetic freedoms. By the late 1 990s design experiments had become more virtual: new computer software, the origins of which are also to be found in the high-tech laboratories of the aerospace indus­ try, rendered possible the development of com­ plex forms that were very difficult, indeed even impossible, to realise using traditional building materials. The amorphous "blob" became the symbol of a generation of architects: wall, roof and floor merged into one form and called for new, flexible properties in structure and sur­ face. To date, the manufacturers of building materials have hardly reacted to these new trends. The architect must therefore devise ind ividual solutions alone - and take the responsibility. This demands a high degree of personal commitment and idealism. The architect as "building materials scout" can become a job in itself, like the post of "Materials Manager" at the Rotterdam offices of OMA; the manager 's task is to handle all the develop­ ments in materials and the practice's contacts with manufacturers. Or the architect could "just

The architect as building materials scout

walk around with eyes wide open and gather information to be recalled as and when need­ ed", which is how Berl in-based architect jOrgen Mayer H. describes his source of inspi­ ration. "Magazines, books or DIY store, discus­ sions with experts from specific fields such as shipbuilding - the boundaries are fluid ." Thermosensitive paint

jOrgen Mayer H. works consciously with the transformation of surfaces into new contexts. His use of thermosensitive paint spans the boundaries between people, spaces and objects. He was stil l a student when he designed a facade that reacted to temperature fluctuations by changing colour. His "housewarming" exhi­ bition in a New York gallery in 1 994 gave him the opportunity to realise this concept. The paint - a technical product designed to reveal overheating on machine parts - originated in the laboratories of NASA. In his exhibition, this special paint - adjusted to react to body tem­ perature - was applied to the walls and doors. Visitors to the exhibition left behind temporary white patches - imprints of those parts of the body that had made contact with the paint. He developed this interior surface treatment into a covering for chairs, the so-called HeatSeats, and also for bed linen (figs A 2.3 and A 2 . 4) . The orig inal idea of decorati ng facades with this paint had to be d iscarded owing to the material's insufficient resistance to ultraviolet radiation. In the opinion of jOrgen Mayer H., innovations in materials are easier to implement internally than they are externally: "". because here the requirements in terms of liability and guaran­ tees are not as high as for external applica­ tions. In the case of innovations, the clients' guarantee demands are d isproportionately higher than for conventional materials, which cal ls for a huge amount of work to convince them. Graphic displays and reference samples represent important aids in this respect." jOrgen Mayer H. knows what he is talking about. He is currently working on the transfor­ mation of a nutty chocolate spread into a desig n for the University of Karlsruhe. The structure of the cafeteria is based on the "Nutellagram": when a nutty chocolate spread ( Nutella) sandwich is pulled apart, thread-like connections ensue between the sol id top and bottom parts ( i . e . slices of bread ) . I n the search for a surface material corresponding to the elasticity of this image, the architect hit upon the idea of a synthetic coatin g : liquid poly­ urethane is sprayed over an inexpensive timber backing to form a homogeneous, skin-like sur­ face.

A 2 .3

A 2.4

proofing roofs, is used here on horizontal and vertical surfaces to cover the entire buildi n g . The underlying structure is a conventional assembly of calcium s i l i cate bricks, precast concrete elements and cement render. Thi s utility building had to comply with strict stipulations: the external d i mensions had to be kept as compact as possible and had to match exactly the sizes of the techn ical equipment i nside. The opportun ities for architectural expression were therefore restricted to the sur­ faces of the building. The polyurethane skin results i n a seamless, monolithic appearance. I ndividual elements such as doors, which con­ vey the scale, are lost in this large format. Nor­ mally, isolated bui ldings such as this are tar­ gets for vandalism. "was 8" does not attempt to defend itself, but instead invites utilisation: its sides embody various functions and therefore can be used as a vertical playing field for those forms of youth culture that are undesirable on other buildings. A basketball basket, a climbing wal l , peepholes - the hardwearing skin amal­ gamates all these elements both architecturally and technologically. The sprayed synthetic envelope makes tradi­ tional facade details such as flashi ngs unnec­ essary. Rainwater is allowed to cascade down the building at random, creating an almost sculptural display on the days on which it rains in the Netherlands (average: 1 34 p.a.). "The material permits a d ifferentiation in the facade, which sti l l appears uniform, " is how Kamiel

Klaase, co-founder of NL Architects, describes the aesthetic advantages of the envelope. It was in the 1 990s that NL Architects began researching the possi b i l ities of using rubber and synthetic materials for architectural appli­ cations. I nspiration for the black finish to "was 8" came from the immediate neighbourhood of the plot itself. The fields around the site are used for agriculture, and after harvestin g , the bales of hay are wrapped in black plastic and weig hted down with old car tyres. The building therefore fits in well with the prevailing colour and material language of the local scene. Kamiel Klaase explains the design process: "Naivety is the starting point. It begins with minor fantasies and brainstorming, and then you have to find the specialists who can realise the idea. ". Many of our elements are materials 'recycled' from another context. That i s the sim­ plest form of design: simply change the operat­ ing instructions!" "Baroque high-tech" made from expanded polystyrene foam

Maurice N io from Rotterdam goes one step fur­ ther in the construction. In 2003 he desig ned the largest-ever building built entirely of plastic. His 50 m long bus terminal in Hoofddorp (see Example 1 1 , page 224-25) , lovingly christened by him as "the amazing whale jaw", consists of an expanded polystyrene foam core with a cov­ erin g of g lass fibre-reinforced polyester - not unl ike the construction of a surfboard.

=

Seamless synthetic coatings

NL Architects used the principle of the plastic skin for the first time on the "was 8" heat exchanger station in Utrecht (fi g . A 2 . 5 ) . The material, which bridges over cracks and was originally developed as a material for waterA 2 .5 15

The architect as building materials scout

A 2.6 A 2.7

Bus termina l, Hoofddorp, NL, 2003, NIO CNC milling of the expanded polystyrene foam for the Hoofddorp b us term in al A 2.8 "Prada foam" product development: gypsum tes t A 2.9 "Prada foam ", scale 1 : 1 A 2 . 1 0 Translucent concrete A 2 . 1 1 Prada Store, Los Angeles, USA, 2004, OMA

I n terms of architecture, the structure is difficult to classify. "To me this is Baroque high-tech the positive feeling of modernism a la Oskar Niemeyer coupled with a type of voodoo CUl­ ture," is how Maurice Nio himself descri bes the building (fig . A 2.6) . "When we develop a project, we start with an emblematic picture that drives the whole project forward. We i mmediately also think i n terms of the materials that could fit this picture - the form as such is not so important; that simply happens at some stage." The architects wanted to create a strong , dynamic i mage t o counter the normal picture of a bus stop - a ubiquitous uti l ity structure nor­ mally desig ned to be as neutral and inconspic­ uous as possible. The original plan was to use concrete, but the complex formwork require­ ments exceeded the budget considerably. On the lookout for alternatives, Maurice Nio was i nspired by a LEGO building kit, and began to break down the structure into modules. The construction is almost completely open in all three dimensions, l i ke a three-dimensional roof - there is only a small enclosed restroom for bus drivers. A manufacturer of swimming pool articles and a boatbu i l der provided Maurice Nio with the right material and the technology to produce the components. The load bearing foam materi­ al is extremely l i ghtweight and inexpensive, and can be machined with a five-axis CNC m i l l­ ing machine (fi g . A 2.7) in order to produce the complex, partly undercut forms . More than 1 00 i ndividual parts were worked out in a computer model and fed directly into the milling machine. All features such as recesses and benches were integrated i nto the prefabricated surface. On the building site, the parts were anchored to a timber plinth and g lued together in situ . "The most important thing you need to carry out such a project is a good team of people who believe in the idea , " says Maurice Nio. "The team is a close and sensitive network made up of cl ient, contractor, subcontractors and archi­ tect - and all with the courage to take a risk. I n the end, the building could not b e b u i lt perfect­ ly; there are several details that are not quite correct. But it is precisely this beauty in imper­ fection that I l i ke - just like a wrinkled face tells us something about a person's l ife. " The transfer o f an existing technology from boatbuilding to a building in this example brought about a new way of thinking about design and detaili n g . The working of the mate­ rial was tailored to the needs of the project. But what happens when the surface itself becomes the object of the design? What happens when the architect is also the inventor of the material? Again, those involved need stami na, coopera­ tive industrial partners and clients, and must be prepared to take risks. This was the case in the Rem Koolhaas project for Prada: two large stores in New York and Los Angeles required new concepts in order to redefine the Prada brand , to create exclusivity and a new identity.

A 2. 1 0

16

Virtual measures were added to the traditional interior design brief: research into shopping trends, the conception of the Prada website, even the development of new types of exclu­ sive materials, e . g . shelving made from solid, cast synthetic resin, silicone mats with a bub­ ble structure, and the so-called Prada foam, a l i g ht green polyurethane material whose struc­ ture oscillates between open and closed, posi­ tive and negative. "Prada foam" made from light green polyurethane

The development began with one of the count­ less design models at scale 1 :50 in which a model building foam was tested as a wall or display element. This foam - an open-pore, beige-yellow material - is normally used on urban planning models to represent areas of shrubbery and trees. The surface proved to be fascinating, especially when lit from behind, and that initiated a period of intensive research into how to transform this material into scale 1 : 1 . In other words, the orig inal belonging to the model had to be found, or rather devel­ oped. Countless tests were carried out on the most diverse materials and surfaces: air-filled bal loons as voids in a gypsum structure (fi g . A 2.8) , soft s i l i cone, chromium-plated metal , rubber, g loss, matt, opaque or translu­ cent surfaces. Several companies were involved in the industrial realisation of the mate­ rial. The prototypes were manufactured from plastic and finished by hand in the architects' Rotterdam offices. The aim was to check the shape and position of the holes once again according to aesthetic criteria and - where necessary - to regrind the material until the appropriate permeab i l ity and appearance was attained exactly. The 3.0 x 1 .5 m panels were subsequently measured and fed into a compu­ ter as a 3D structure. This data served as the d i g ital basis for producing the final CNC-milled negative moulds. The moulding compound for the "Prada foam" was a greenish translucent polyurethane compound specially developed for the project that met the necessary fire resistance requirements (fi g . A 2.9) . After two years of preparatory work, the materi­ al was first revealed to the public in 2004 at the opening of the Prada store on Rodeo Drive in Los Angeles (fi g . A 2 .1 1 ) . OMA and Prada share the rig hts to the new development; nei­ ther can use the material for further projects without the approval of the other. The exclusivi­ ty of the material is therefore guaranteed . Translucent concrete

Following a spontaneous impulse and without the financial backing of a large organisation like Prada, a young architect from Hungary developed an idea for a new material almost out of nothi n g . I n 2001 Aron Losonczi submit­ ted his translucent concrete idea for a Swedish postgraduate scholarship promoting new approaches i n art and architecture. He had been inspired by a work of art he had seen shortly before: fragments of glass cast i nto a

The architect as building materials scout

block of concrete, and with some of the frag­ ments left protruding to catch the light. The concrete appeared to be perforated and there­ fore lost its massiveness. Aron Losonczi was granted a scholarship to develop his idea at the Royal University College of Fine Arts in Stockholm. He studied the prin­ ciple of d i recting l i g ht and built the first proto­ types - about the size of a standard brick­ using gypsum and g lass fibre. Further proto­ types followed, this time in concrete, and after two years of research he applied for a patent for his light-directing concrete. Back in Hungary, the first large panel was made by han d : 1 500 x 800 x 200 mm and weighing 600 kg . The fibres were laid manually in the fine concrete in layers perpendicular to the surface. The amazing thing about this material is that it appears incredibly delicate and transparent, although only about 4% of the concrete is replaced by g lass, and therefore the load bearing capacity of the concrete is hardly affected . The material is currently under­ going various trials - so far successful; it has a compressive strength of 48 N/mm2 . The princi­ ple is simple and fascinating at the same time: light is directed through the fine glass capillar­ ies from one side of the concrete to the other. The concrete appears to be illuminated from within, shadows and silhouettes appear quite distinctly on the non-illuminated side (fig . A 2. 1 0) . The brand-name "LiTraCon" - an acro­ nym of Light Transmitting Concrete - was invented for the industrial production and mar­ keting of this new material.

that such experiments can bring. In this respect, the establishment of strategic partner­ ships is without doubt beneficial for both sides: the architect profits from the technical expertise of the company, and the company can tap new markets with the architect's ideas. For a number of years we have been witness­ ing designers' tremendous fascination for sur­ faces and new materials. This is revealed not only in the numerous publications, symposia, trade fairs, research and consultancy offers on this subject, but also in the designs of the new generation of youn g architects. The surface often forms the starting point for a design, be it the external cladding to a facade or an internal lining. Materials have always been a central theme among architects, but the handl i n g of this theme has become much more cosmopoli­ tan and experimental. Where did this materials "trend" orig inate? It is possible that new approaches were required to enrich the amorphous, arbitrary forms generat­ ed by computer designs by adding haptic qualities again. In our over-informed world there is without doubt a longing for the sensual, for the d i rect experience. I n this respect, sur­ faces are the d i rect mediator between people and architecture; this is where we can touch the b u i l d i n g . A t t h e same time, there i s also t h e danger that the surface will become more and more super­ ficial, reduced to just an eye-catcher, simply a gimmick. What might appear very decorative in

high-gloss publications, could in reality be nothi n g more than cladding to trivial, trite archi­ tecture. On the other hand, good-quality archi­ tecture has always been distinguished by a close conceptual relationship between percep­ tion, space and materials which transcends all definitions of style or personal taste. An inter­ esting material cannot create interesting archi­ tecture on its own. In this sense, the well-known slogan of the concrete industry can be extend­ ed to cover the entire spectrum of building materials: material - it depends what you do with it.

Talking about the long way from the idea to the marketable product, A ron Losonczi says: "It was very d ifficult at first to convince the compa­ nies to work with me. The larger a company, the more d ifficult it is to get in touch with the right people. It was certainly important that I had built the samples as prototypes and my idea could therefore not be rejected out of hand as crazy. Nevertheless, up until the first major papers, the companies d i d not take the product seriously. In the final year there was then a boom in publications, and in December LiTraCon was presented as one of the ' I nnova­ tions of the year 2004' by Time Magazine." But the success story of A ron Losonczi 's light­ directing concrete is not yet over. In the mean­ time he has found a manufacturer who wishes to produce the concrete on an industrial scale. We await with excitement the first buildings with translucent concrete walls . . . New materials - from the idea to the product

The story of the development of translucent concrete shows the stony road from the i dea to the product: however much the idea of the material may fascinate the architect, the build­ ing materials industry works purely according to economic criteria governed by batch sizes, sales and profits. If the industry was to look beyond the direct costs-benefits calculation, it would often see the long-term gain in prestige A 2. 1 1 17

The critical path to sustainable construction Peter Steiger

The term "sustainabil ity" was coined in 1 987 by the World Commission on Environment and Development, the "Brundtland Commission" . What this means is: " . . . to make development sustainable - to ensure that it meets the needs of the present without compromising the ability of future generations to meet their own needs." At the U n ited Nations Earth Summit in Rio de Janeiro in 1 992, sustainable development was defined as the improvement of the l iving condi­ tions of people in economic and social terms but in harmony with the long-term safeguarding of the natural foundations for life. Today, the term sustainability awakens the hope of a trou­ ble-free interaction between an efficient econo­ my, a sound society and an intact environment. The global concept, which is formulated in Agenda 21 , should be implemented on a local level with a responsibility towards the environ­ ment and future generations. As the forces of nature are sometimes experienced as a threat and generate a feeling of helplessness, the prospect of an intact environment awakens hid­ den longings in many people. However, this ideal state can no longer be produced throug h the realisation of the global concept of Agenda 21 . But, looked at realistically, which goals can we pursue throug h sustainable development? What should we call them? I nterestingly, there is no precise term for the "maximum utilisation of naturally occurring environmental energy", for the "lowest technically achievable value of environmental impact" (for unavoidable energy conversion processes) , or for the "lowest possi­ ble consumption of resources for the maximum quality of a structure" (for sustainable methods of construction ) . But without such terms we are also lacking designations for a targeted way of thinking and acting and also information about those forces that can del iver results in this issue. Where are we growing to?

A 3.1

A 3.2

A 3.3 A 3.4

18

Tools and in for mation syste ms for t he work ph ases o f the Ger man sc ale of fees for architects and engineers (HOAI) Lo am structures (these ex amp les are in Morocco ) exhibit opti mu m conditions reg arding co mfort and d ur ability, even fro m the modern vie wpoint. At the s ame ti me, the environ ment al i mp act - fro m pro­ duction to disposal of materi als - is mini mal. Even with sust ain able for ms of construction , build ­ ings still h ave to be maint ained and c ared for. Deserted houses and settl e ments g r adu ally disin­ tegrate and return to the l andsc ape.

Even the first report of the Club of Rome ( 1 972) questioned the sense of everything technically feasible. However, it was not until the mid1 980s that we managed to shrug off the con­ viction that energy consumption went hand in hand with economic growth. Today, this recog­ n ition must be transferred to the consumption of all resources as a whole because if econom­ ic g rowth is only possible with a constant increase in the consumption of resources, then economic g rowth must be restricted. From the point of view of ecological sustainabil­ ity, the term "growth" must be replaced by words like retreat, sacrifice, limitation, avoid­ ance or reinstatement in order to formulate an adequate ecological objective. However, all these terms have negative connotations in the general use of the language because success is harder to identify in the form of restraint than it is in the form of accompl ishment. Conse­ quently, such terms do not trigger any positive­ ly motivated actions. Typically, there is also no word for the opposite of economic growth that in the same way prom­ ises hope of greater prosperity but without the

g rowth associated with this in the past. The term "qualitative growth", which fills the void as a placeholder, at least points to the expectation that an increase in prosperity includes not only quantitative but also qualitative components. But terms that are not associated with values and imply benefits and success are not suita­ ble for the advancement of science and cul­ ture. Thi s is clearly shown by the word "sustain­ ability", from which all sides currently derive their own particular interests. The tallest sky­ scrapers are given the "sustainable" award when their huge steel-and-glass facades include attri butes for the passive or active use of solar energy. In this way, emphasising indi­ vidual aspects while ignoring the overriding objective helps those terms that can only be measured i n terms of benefits and success. The goal of present and future generations of architects must be to achieve maximum quality i n the finished products with a maximum spar­ ing of resources. Therefore, the motto for con­ sumption of resources "less is more" coined by the architect Ludwig Mies van der Rohe will no longer be just the technically feasible, but instead the actually necessary. I n the building sector in particular, the work required to achieve high quality consists not only of labour costs, but also the inte l l igent deployment of capital and suitable means of production. Quantitative and qualitative comparisons to ensure a thrifty consumption of resources should therefore be the focus of our construc­ tion ideas in order to create the foundations for measuring complete building works under sus­ tainable and qualitative premises. Developing tools for the selection of building materials

I n order to be able to measure and evaluate the consumption of resources in building works, a method of assessment based on the primary energy input (PEI) of a building material was developed as long ago as 1 982. The compari­ son of various building materials by means of the primary energy input represents an impor­ tant basis for l ife cycle assessments (LCA) . In order to assess buildings and structures as a whole and to enable the choice of those con­ struction methods and forms with minimal envi­ ronmental impact, a model was developed in Switzerland in 1 995 (SIA Documentation D 0 1 23) which comprises a scientific-quantitative part, the "index", and an assessment of the q ualitative serviceability, the "profile". By con­ verting the respective pollutant emissions from a construction into equivalent variables (C02 , S0 ) the environmental effects (e.g. global 2 ' warming, acidification of soil and water) can be compared. Today, we increasingly need computer-assist­ ed information systems to enable ecological and economic comparisons of individual forms of construction and overall concepts, and to meet the current thermal standards. As a fur­ ther development of SIA D 01 23, an online component computation system is currently

The critical path to sustainable construction

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2 35%. At first, the use of recycled materials appears to be sensible in principle. A num ber of varia­ tions are compared here for a practical deSig n situation :

result: the zero line of the d iagram represents normal-weight concrete without recycled aggregate; the vertical bars represent the improvement or worsening of the effects as percentages. It can be seen that owing to the transportation required and the extra cement, in the most important impact categories the environmental impact rises as we increase the content of recycled material. Only the indicator for the consumption of materials decreases. So the use of recycled aggregates in concrete relieves the burden on the environment only when the aggregates are obtained from a near­ by site « 1 00 km) and if there is a scarcity of aggregates in the form of gravel or sand in the reg ion of the batching plant, which it could also be due to l i m its placed on the quarrying of such materials. This example clearly reveals that even after drawing up a comprehensive life cycle assess­ ment, the results are not necessarily generally applicable to all projects or all regions. Each individual case m ust be checked to establish whether ind ividual effects play a particular role. Comparison of costs

Cost comparisons in building are generally per­ formed by way of the well-known cost estimate, cost calculation and cost control. The crux of the problem in cost comparisons i s the estimate of the cost of usage because this requires knowledge about the anticipated costs of main­ tenance and renewal. Several computer-assist­ ed approaches based on the costs breakdown according to D I N 276 are available. [4] How­ ever, these do not permit any flexible treatment of the durability of building components or lay­ ers (in a sense of optimising sustainability). The costs including cost of usage and cost of d is­ posal/demolition are known as the l ife cycle costs. In conjunction with efforts to harmonise the methods and to develop sustainability indi­ cators for buildings, a dynamic, quality-related durabi lity estimate for building components and products is currently u ndergoing develop­ ment. [5]

Detail design

normal-weight concrete, grade C 25/30, without recycled aggregates concrete, grade C 25/30, with 35% recycled aggregates obtained locally « 1 00 km) concrete, grade C 25/30, with 35% recycled aggregates not obtained locally (> 1 00 km) concrete, grade C 25/30, with 1 00% recycled aggregates (can be approved for i ndividual projects) obtained locally, plus higher cement content As the recycled aggregates should be as uni­ form as possible and hence are best obtained from a single demolition site, the material may well have to be transported over long d i stanc­ es, which is why the distance parameter < 1 00 km/> 1 00 km is relevant. Fig A 4.2 shows the

Selecting products and processes to save mate­ rials and minimise environ mental impact:

Planning of building services (electrics, hoV cold water, heating) to save materials through an optimised arrangement of sanitary and supply zones, service routes and supply lines. Water-saving systems. Reducing the conversion and renewal work during the period of use by choosing d urable and reparable component forms that al low flexi bility of usage. Building with recycl i n g i n mind by using spl it­ table, mechanically detachable component layers or homogeneous material assemblies.

Hygiene and health, interior clima te:

Ventilation systems and ventilation rates. Optim isation of the interior climate conditions through the release of heat over a large area without convection. Safeguarding of a comfortable and healthy i nterior c l imate through optimised ventilation design, optimised supply and removal of heat, plus the provision of sufficient storage mass. Optimisation of sound insulation. Quality assurance for detail design work

The optimisation targets of the long-term guar­ antees for the functions of building compo­ nents, the ease of repair and the flexibil ity regarding change-of-use requirements can be grouped together under the heading of durabil­ ity. This variable which has to be estimated is, of course, not a fixed value, but instead to a large extent dependent on the quality of design and workmanship. Depending on the quality assurance measures, it is not usual these days to replace wooden double-glazed windows until after 1 0, 20 or even 50 years. Likewise, in an entrance zone a floor covering with adjacent walk-off mats wi l l last much longer than one without such mats. As already explained, it is vital to know the estimated durabil ity of a build­ ing component when assuming renewal cycles and hence for the chronological part of the life cycle assessment and life cycle costin g (LCG). The q uality to be optimised here is commonly referred to as the experience of the architect, engineer or contractor i nvolved. Unlike with the evaluation of the environmental effects of mate­ rials during extraction of raw materials, produc­ tion and d isposal , there is still no uniform tool for assessing the technical-constructional qual­ ity attained and the achievable useful l ife of a building component; however, research into this is ongoi n g , and this work allows us to dis­ cern a n u m ber of fundamentals. One important criterion for optimising the dura­ b i l ity is the more or less successful concur­ rence of properties and risks (sensitivities) of the material on the one hand, and the function­ al req u i rements and loads on the building com­ ponent on the other. The result improves as the number of loads coinciding with sensitivities decreases, and the number of desirable func­ tions coinciding with the typical properties of the material increases. This leads to a second criterion: how the poten­ tial damage resulting from the convergence of particular loads and material-specific risks i s compensated for in technical a n d construction­ al terms. The third criterion concerns the question of the detachability of connections in a building com­ ponent and hence the issue of reparability and partial renewal. The q uestion regarding the respective main uses of the building compo­ nent are important here. In the case of surfaces in particular, it is very l i kely that one of the main uses will b e aesthetics, which can lead to a fashion-, taste- or identity-related replacement

25

Criteria for the selection of building materials

of otherwise fully functional and trouble-free surfaces or products. A similar situation is found with components such as sanitary appli­ ances, which are heavily influenced by culture. In such cases mechanical , easily detached connections should be chosen in order to mini­ mise the consumption of materials in the event of replacement. In the case of concealed, pure­ ly technical components such as waste-water pipes, waterproofing systems or load bearing components, it is the technical dura b i l ity that must be g iven priority. I ndustrially manufac­ tured composite elements may represent an improvement in quality, although they should always be checked for the separability of the different materials to aid recycl i n g .

A 4.3

Comfort index

Tendering, award of contract and work on

I n recent years, the boundary conditions responsible for a healthy and agreeable i nterior climate have been standardised in the regula­ tions with increasing precision, and have been fleshed out with target values. This concerns such important aspects as the airtightness of buildings (measured using the blower door technique to EN 1 3 829) , the m i n i m u m air change rate (0.6-0. 7 times the volume of the room per hour for removing pollutants and car­ bon d ioxide from the i nterior air) , or the avoid­ ance of cold bridges and mould g rowth (by using appropriate calculation methods to DIN EN ISO 1 0 2 1 1 . Moreover, the perceived comfort in an interior depends on the air speed of the convection currents, the cold air radiated from walls and soffits, and the temperature stratification. The interaction of the individual influences plus their physical effects and individual, subjective per­ ceptions cannot be solved with simple, physi­ cal relationships or algorithms. Therefore, the subjective perceptions of volunteers were included in D I N EN ISO 7730 for determi n i n g the thermal comfort conditions. T h e P M V (pre­ dicted mean vote) index represents an assess­ ment of the thermal comfort and is formed by combining several physical boundary condi­ tions. The PPD (predicted percentage of dis­ satisfied) index is a statistical function of the PMV and describes a forecasted figure for d is­ satisfied persons in per cent. We distinguish between three qual ity categories: A, B and C. These are the same as the climatic req uire­ ments of both D I N EN ISO 7730 and Swiss standard SIA 1 80, which should be used when planning climate-regulating forms of construc­ tion, e.g. for the desig n of thermal storage masses available in the interior, when conceiv­ ing the removal of heat in the summer, the ven­ tilation systems, or the design and construction of thermally insulatin g components and their internal surfaces.

site

26

Selecting products and processes to save mate­ rials and minimise environmental impact:

Safeguarding of the long-term retention of value and sustainable functionality of forms of construction and bui lding components throug h inviting tenders for qual ity-controlled building materials, products or components and throug h a detailed functional description of the building works desired. Selection of solvent-free chemical products. Avoidance of products with environmental and health risks in the extraction and produc­ tion processes. Low-waste buildi n g , recovery of residues. Ensuring a low-noise and low-dust building site, avoidance of groundwater contamina­ tion, pollution and dangerous methods of working. Hygiene a n d health, in terior clima te:

Selection of non-hazardous and Iow-emissi­ ons surface materials. Avoidance of materials with higher fire risks caused by high smoke densities or corrosive and , in addition, toxic fumes. Prevention of radon loads in the building from the subsoil throug h correspond i n g sealing measures to the ground slab and the base­ ment walls. Avoidance of electrostatic fields and surface charges during usage throug h the specifica­ tion of conductive products for floor cove­ rings or office fittings in the tender. As a rule, it is the tender documentation that first specifies details to the extent that specific products, connections and assembl ies can be d istinguished for the internal fitting-out trades. In the case of public-sector building projects especially, the nomination of specific products is only permissible in exceptional cases, and they are mostly not known until the bid is received - provided the req u i rements for nam­ ing products were correctly specified in the tender documents. The ecology and hygiene req u i rements the products should meet must be known and specified in full during this stage

of the project at the latest. The interior air generally contains a broad spectrum of organic materials as wel l as dust and fibres. The source of these is people them­ selves ( breathing, body odour) and the activi­ ties people are apt to perform indoors, e . g . smoking, cooking, etc. , but also b u i l d i n g mate­ rials and internal finishes and fittings, which may g ive off chemical compounds. Depending on their concentration and composition, the internal air can become overloaded, which may i mpair the comfort or even the health of the occupants, and in this respect poor climatic conditions reinforce such negative influences. Such i mpurities are becoming a problem as buildings become more airtight and the air change rates decrease. Airborne pollution from organic substances

Emissions from surface coverings and coatings on buildings, assembl ies, furnishings and fit­ tings can give rise to organic contamination. Building components made from organic mate­ rials in particular, e . g . plastics, paints or adhe­ sives, contribute significantly to airborne pollu­ tion. In order to develop an evaluation tool for this, a list of approx. 1 50 volatile substances (volatile organic compounds - VOC) [6] fre­ quently encountered was drawn up. These are d ivided into the following classes (based on boiling point) : very volatile organic compounds (WOC), boi l i n g point < 0-50 to 1 00°C volati le organic compounds (VOC) , boi ling point 50-1 00 to 240-260°C semi-volatile organic compounds (SVOC) , boiling point 240-260 to 380-400°C The sum of all these substances is known as the total VOC (TVOC) . As toxicolog ical studies are lacking for the majority of these substanc­ es, and therefore there are no useful limit val­ ues available for interiors, the German Environ­ mental Agency has set target values for TVOC measurements which are applicable in Germany: short-term ( 1 -2 months) : approx. 1 500-2500 IJg/m2 long-term ( 1 -2 years) : approx. 200-300 IJg/m2

Criteria for the selection of building materials

Owing to the highly disparate toxicities of the i ndividual substances, evaluations of individual substances are currently bein g carried out one by one within the scope of the initiative "Euro­ pean Collaborative Action: I ndoor air qual ity and its impact on man". According to this, two guide values for i ndoor air qual ity - RW I (desir­ able value) and RW II ( intervention value with clean-up recommendation) - are specified for the individual substances. To date, substances such as styrene, benzene, naphthalene and formaldehyde have been assessed. The VOC measurements are the final results of evaluations and are not suitable as planning values. To help choose ind ividual materials rel­ evant to surfaces in a tender, a method of eval­ uation was developed recently in which the products themselves can be classified and cer­ tified on the basis of VOC test chamber meas­ urements (prEN 1 3 41 9) over a period of 28 days. According to this, building products must exhibit the property "suitable for use in interi­ ors" corresponding to an evaluation scheme specified by the German I nstitute of Building Technology ( D I Bt) . This property must be veri­ fied for products requiring approval using test chamber measurements provided by the man­ ufacturers and must be declared in the product specifications. The boundary conditions for the measurements are to be stipulated and recorded by the labo­ ratory appointed to do the work based on the DIBt criteria. This method of evaluation can be specified for primary and surface materials such as floor coverings, door leaves, faces of built-in items, and wallpapers. Using the product specification, the final emis­ sion values reached in i nteriors cannot be sim­ ulated with adequate reliabil ity, which contrasts with the building performance planning of the interior climate. The design of internal surfaces is therefore carried out primarily according to the principle of avoidance, i .e. by concentrat­ ing on low-emissions and zero-emissions mate­ rials (e. g . all mineral surfaces) , and where low emissions are acceptable, by choosing certi­ fied products. Numerous certification systems are already in place, usually in the form of trade organisation awards, e . g . the Emissions Code for floor coverings and adhesives ( EC-1 ) , the certification for wal l paints with zero emissions and zero solvents (ELF), or the RAL environ­ ment symbol for paints issued by Germany's Environmental Agency ("Iow emissions and low pollutants" RAL UZ 1 2) . Besides the organic impurities in the interior air, man-made mineral fi bres or organic fi bres rep­ resent another possi ble hazard. Since 1 995 the formulations of mineral insulating fibres, for instance, have been changed in such a way that the so-called bio-persistence (presence of ultra-fine fibres in the lungs or pulmonary fluid) and hence the carcinogenic potential was able to be reduced in accordance with the size defi­ nition of the World Health Organisation (WHO). [7] Of course, even coarser fibres represent a potential risk for human respiratory tracts. Fibre

i nsulating materials are used internally mainly in l i ghtweight partitions, suspended ceilings, floor insulation and window junctions. These assemblies and details must be designed to prevent the fibres getting into the interior air, i .e. sealed. As a relative scale for the contamination in a room, the background contamination of the exterior air - which varies considerably from region to region - can be used (e. g . in Berlin approx. 300-500 WHO-definition fibres/m3) . Owing to the passage of air through joints and junctions, this background contamination usu­ ally exists i nside buildings as well and should not be worsened by adding fibres from building components and materials.

Application of optimisation tools

References: [1 J Total Volatile Organic Compounds [2J European Collaborative Action: Indoor Air Quality and its Impact on Man (ECA) [3J The FSC certificate regulates the sustainable management of forests. It is often demanded by public-sector clients in Europe in conjunction with the "Chain of Custody" trade certificate. [4J GEFMA 2000: Kostenrechnung im Facility Manage­ ment; PLAKODA, Planungs- und Kostendaten; Schmitz, Heinz, et a l . : Baukosten 2004 - I nstandset­ zung, Sanierung, Modernisierung, Umnutzung, Essen, 2003 [5J ISO/TC/59: Item Buildings and Constructed Assets ­ Sustainability in Building construction - Sustainability indicators [6J A list of the TVOC groups can be found in the g lossary, p. 269 [7J Corresponding rock wool fibres are declared as having "reduced bio-persistence". Glass wool fibres are characterised by the "carcinogenicity index" (Ki), which may not be less than 40: Ki ;;, 40.

The information structure required for the appli­ cation of the aforementioned optim isation tools is being constantly improved by the g rowing declaration requirements for building products. The introduction of additional certification sys­ tems by the manufacturers, the provision by trade organisations of data records for life cycle assessment calculations and the devel­ opment of standardised methods of measure­ ment have led to the methods of evaluation bein g included in the design and construction phases of building projects without any signifi­ cant time and cost d isadvantages. However, owing to the information that must be gathered, the appointment of appropriate experts as con­ sultants for drawing up comparative l ife cycle assessments for important components or for the ecological quality control of tenders and workmanship is recommended for larger con­ struction projects. Besides the ecologically optimised selection of main materials and components, another focus of the optimisation work is the writing of the ten­ der documents, the product declarations of the suppliers and the constant inspection of work­ manship. The finished structure can comply with the sustai nability requirements only if these have been stated in detail in the tender docu­ ments without reference to any products. I n numerous projects i t has proved beneficial to demand - at the latest after opting for a certain bid - a binding declaration for the products and by-products to be used with the help of a list of products ( i ncluding the safety and certifi­ cation information ) , and to make this a compo­ nent of the contract award and contract docu­ ments. Only after target values regarding pri­ mary energy i nput, comfort or hygiene have become part of the contract can they be checked upon completion of the structure and, if applicable, be demanded as an agreed property within the scope of the warranty. I n future, defects in the environmental quality of buildings will increasingly represent a verifiable design error. A 4.3 A 4.4

Transport distances should also be considered when selecting building materials. Destruction of the environment in the tropics

27

The development of innovative materials Dirk Funhoff

� Physical materials flow - to building site - Influence on choice of material - for building

The building industry is not regarded as an innovative sector. According to a survey of Swiss companies carried out in 1 999, the pro­ portion of sales of i nnovative products in the building sector is just 1 0. 7 % , which does not compare favourably with the average figure of 37. 1 % for all sectors of industry. Just 24% of the companies polled carry out R&D work, compared to 49% for industry as a whole. [ 1 ] High g rowth rates in the building industry are a thing of the past. In Germany low demand has resulted in many years of stagnation. Extensive regulations, standards and approval proce­ dures make changes difficult; i ncreasing com­ plexity puts up the costs. At the same time, people are sti l l looking for hig h-qual ity faci l ities for work and play. New findings in the field of housing physiology demand modified prod­ ucts; high demands need to be satisfied with­ out excessive price rises. In the light of all this, the need for innovations i s rising. This chapter attempts to i l lustrate the develop­ ment of i nnovative materials for homes and building, and to foster the mutual understand­ ing of those involved in this process. What is innovation?

A 5.1 A 5.2

28

Simplified diagram of the value-creation network in the building industry Thermal conductivities of various materials

The term "innovation" is frequently used simply as a synonym for "new" or "novel". But new­ ness, i . e . the invention of a new material or new effect, is not enough by itself. I nnovation is the establishment in the marketplace of a new technical or organisational idea, not just the invention of such. [2] This economic aspect explains why innovations offer great chances; i nnovators enjoy a better reputation i n the mar­ ket (also for their standard products) and they are attri buted greater competence, which in turn is reflected in a higher acceptance of their products. The term "innovation" is frequently used simply as a synonym for "new" or "novel". But new­ ness, i . e . the invention of a new material or new effect, is not enough by itself. I nnovation is the establishment in the marketplace of a new technical or organisational idea, not just the invention of such. [2] This economic aspect explains why innovations offer great chances; innovators enjoy a better reputation in the mar­ ket (also for their standard products) and they

A 5. 1

are attributed greater competence, which in turn is reflected in a hig her acceptance of their products. Marketing success is vital to innovation. It is therefore not sufficient merely to describe which new materials or technologies exist. [4] Their development takes place within certain boundary conditions, which restrict the use and availability of the new materials. Placing these products in a fresh context is "new", but the desirability triggered is often neither sensible nor satisfyin g in the long-term. And if the mar­ keting success is not realised, then we have no innovation . If those involved in innovation proc­ esses and the value-creation network of the building industry could learn to understand each other better and improve the coordination of their processes, it would open up a major chance for i nnovation. Boundary conditions

Innovation on the material side is advanced by researchers or developers in the laboratories of the raw materials and building materials indus­ tries, even if there are impulses from other branches such as architecture or design. From the scientist's viewpoint, material in the more precise definition means "substance, raw mate­ rial or medi um". [5] From this they (also) create materials whose shape, colour, etc. are adapt­ ed to various applications. Architects and designers deploy these materials in order to create a desirable environment in which to build and l ive. I n order to modify the products to match their ideas, they contact the suppliers. However, the suppliers do not always have the abil ities to influence the underlying "fabric" of the materials because the value-creation net­ work is so complex (fi g . A 5 . 1 ) . Which materials are actually used in building work is decided by those by those working on the building site. The manufacturers of building products or the raw materials suppliers do not play an active role and are seldom called in to answer questions regarding choice of materi­ als. The story is different in the automotive and avi­ ation industries. In these industries the manu­ facturers of the end products hold discussions with components and raw materials suppliers

The development of innovative materials

and define the specifications of the materials. This joint approach g uarantees innovation: when the new material satisfies the require­ ments of, for instance, a car manufacturer, it is also employed in the production of those cars, i.e. the marketing success is highly probable. A primary impetus for this type of development can be found in the structure of these sectors: in the automotive industry the 1 0 largest com­ panies have a global market share exceeding 80%; in civil aviation the two aircraft manufac­ turers Boeing and Airbus rule the market. But the situation is very different in the building industry: with a global value of approx. 3.8 tri l­ lion US dollars, the 1 00 largest companies together accounting for 373 bi llion US dollars enjoy a market share of less than 1 0% . [6] The industry is highly fragmented, the demand very heterogeneous; therefore, an integrated approach is harder to realise. Nevertheless, such a model can be transferred to the building industry. Here again, the objective is, after all, to optimise materials with a view to satisfying human requirements - including "soft" factors such as aesthetics or haptics. But such factors are subjective and difficult to quantify, and therefore have not yet found their way into the industry's development laboratories. I n order to achieve that, users need to know not only which options new materials offer, but also understand how their development functions, which boundary conditions apply and how they can be influenced. On the other han d , develop­ ers in their laboratories must learn to under­ stand better which needs an architect or a designer is trying to satisfy. A researcher is driven by curiosity and an enthusiasm for something new. There is cer­ tainly no great difference here between a researcher and an architect or a designer. Like sport has its motto "further, faster, higher", lab­ oratories work with the maxim "smal ler, l i ghter, smarter" . Basically, the idea is an ongoing improvement of the technical properties of materials. With an increasing understanding of the physical and chemical properties of a material , the researcher is in the position to manipulate these and combine them to form new types of property profiles. The flood of information

In the natural sciences and technology we are currently witnessing an unprecedented explo­ sion of knowledge. According to a study car­ ried out in the 1 960s, the natural sciences grew exponentially between 1 650 and 1 950, i.e. our knowledge doubled every 1 5 years or so. [7] Since the 1 970s growth has slowed and stabi­ lised at a high level. [8] At present, some four million articles dealing with the natural sciences and technology are publ ished every year that 's about 20 000 every working day, [9] and doesn't even include the output of the arts and humanities! These figures show that trying to retain an over­ view of all aspects of knowledge is hopeless the age of the universal scholar is over. Further-

more, it is becoming more difficult to distin­ guish the relevant results from the less relevant. As we know more and more, the input req u i red for new d iscoveries increases (decreasing fringe benefits) . What this means is that funda­ mentally new materials are d iscovered less and less often ; for example, further chemical ele­ ments are no longer "discovered" in nature, but instead briefly "created" in horrendously expensive particle accelerators. Consequently, these days we focus more and more on novel , creative combinations of known materials in order to generate new effects, or transfer effects to other materials. This approach leads to a g igantic number of combi­ nation options, which very q uickly g ives the impression of new technologies and applica­ tions. But many new technologies are old friends i n new g uises; however, their applica­ tion or interpretation in a new context does offer new possibilities and chances. The challenge for the future is to steer the development proc­ ess and turn the many ideas i nto innovative products. Developments in materials

More and more, the R&D departments of indus­ try are under pressure to i mprove their effec­ tiveness, i . e . to identify the right themes and develop these accordingly. I n the meantime, prior to the start of any research , the potential marketin g chances and the potential profits are analysed alongside the technological aspects. Only when the first two factors show a positive result can the developers embark on the ever more costly research work. [ 1 0] I n the first p lace, technological parameters form the guidelines for the development: q uan­ tifiable effects and properties are important prerequisites for a targeted development. Two examples of this are thermal insulation and phase change materials (PC M ) : Thermal insulation

The optimisation of thermal insulation materials is based on a precise analysis of the physical principles of heat conduction. The thermal con­ ductivity of an insulating material depends on the thermal conductivity of the solid (e.g. poly­ styrene, stone), the thermal conductivity of the gas (e.g. air) and heat radiation. In doing so, we assume that convection in the gas i s pre­ vented by suitable measures (foam, fibre com­ posite) . Therefore, we get the following equa­ tion for thermal conductivity: A

=

ASOlid +

Aceu gas

+

"-radiatiOn

As a low A-value represents an increase i n the thermal insulation capacity, the strategy for fur­ ther work is clear: each of the above factors must be minimised, a goal that industry has pursued systematically. A vacuum is the best insulator, followed by gases and solids (fig . A 5.2). All known natural and man-made insulating materials are based

Material

Thermal conductivity [W/m K]

Structural steel Marble

50 3.5

Normal-weight concrete

2.1

Solid clay products

0.96

Glass

0.8

Polyurethane

0.35-0.58

Hardwood

0.2

Polystyrene

0. 1 3 -0. 1 6

Air

0.024

Carbon dioxide

0.0 1 6

Vacuum

0 A 5.2

on this law of physics. From animal skins to high-tech thermal insulation composite sys­ tems, all make use of the same principle. But there are still further opportunities for improve­ ment. On the graph of an expanded polystyrene foam we see that the heat radiation in the infrared range plays a considerable (negative) role, especially when the foam is thin (fi g . A 5.3). I n order t o halt the infrared radiation, infrared absorbers or reflectors can be incorporated into the matrix of the foam - of course without damaging the cell formation or the other good properties of this insulating material. Appropri­ ate methods are available to i ntroduce such infrared absorbers, e . g . in the form of graphite, into the foam beads. It is therefore possible to reduce the thermal conductivity of the poly­ styrene foam even further (fig . A 5.5). IR absorb­ er-modified polystyrene insulating materials can be up to 50% thinner than conventional insulating materials with the same density and same insulating performance (fig. A 5.4) . This proves to be an advantage when modernising existin g buildings, where there is not always sufficient space for an adequately thick layer of insulation. But I R absorber-modified polysty­ rene insulating materials have already been used for new building work too, e . g . in the Petra Winery in Tuscany by Mario Botta. But the developments in thermal insulation go even further. The recognition that cell gas makes a s ubstantial contribution to heat con­ duction (fi g . A 5.3) led to two new approaches aimed at minimising this disadvantage: vacuum i nsulation (complete avoidance of cell gas) nanocel l ular foams (freezing the molecular movement of the cell gas) •

•

The first approach resulted in the so-called vacuum insulation panels (VIP) , which consist of an open-pore core (e.g. silicic acid powder or polyurethane foam) with a gastight covering (see "I nsu lating and sealing", p. 1 39). Owing to its cell structure, the open-pore foam enables the element to be evacuated (fig . A 5 . 1 0) . This means thermal conductivities of 0.004-0.008

29

The development of innovative materials

Thermal conductivity ).. [W/mK]

0.05 0.04 0.03 0.02

�J • • i \

I

\ I

0.01

Cell gas (air)

� �,

�

PS m trix

o o

10

I

-

'1

Infr ed radiition

20

30

40

50 60 Density

- � > '" '" 5°C, high temperatures accel­ erate the hardening process

strengths have been used here to provide a comparison.

84.6

frost resistance are achieved with a value � 0.6. The concrete strength classes to EC2, the strength classes of standard cements and the water/cement ratio are all interrelated.

White cement White cement has the same properties as Port­ land cement but owing to its lighter colour is preferred for fair-face concrete, terrazzo finishes, etc.

D I N EN 1 97-1 divides the cements into classes (Z) according to the minimum compressive strength (in N / m m2 after 28 days, standard prism 40 x 40 x 1 60 m m ) . Depending on the setting process of the various types of cement, the letter N describes a normal initial set and the letter R a high i n itial strength . The types of cement can be basically allocated to the follow­ ing strength classes:

Water/cement ratio The water/cement ratio (w/c ratio) describes the relationship between the quantity of water and Z 32.5 N; Z 42.5 N primarily blast-furnace cement weight of cement as a percentage. This ratio is Z 32.5 R; Z 42.5 R primarily Portland and critical for complete hydration. The value deter­ mines the porosity of the hydrated cement and Portland blast-furnace cement hence the strength. During hydration about 40% of the cement by Z 52.5 N; Z 52.5 R Portland cement only weight (w/c ratio 0.4) is chemically and physi­ cally bonded to the water. I n practice the values lie between 0.42 and 0.75. A hi gher w/c ratio Aggregates and additives/admixtures results in a hi gher porosity, d ue to the water­ filled pores, which impairs the properties of the The nature and size of the g rains added to the mineral binders to form the main constituent concrete. I mperviousness to water and good (65-80% by vol .) determine the properties of a mortar or concrete. ·

•

•

Aggregates

We d ivide aggregates for concrete into light­ weight, normal-weight and heavy aggregates accord ing to their density. Aggregates like sand and gravel consist of rounded, unbroken grains. Chippings and bal­ last, which are produced in mills by crushing larger rocks, are described as angular grains. This type of aggregate also includes grains obtained from recycled concrete.

8 4.7 56

8 4.8

Building materials with mineral binders

Lightweight aggregates Mortar and concrete with lightweight inorganic aggregates exhibit i mproved thermal insulation properties and better behaviour in fire. Tuff, pumices and scoria are some of the natural lightweight aggregates; the man-made ones include expanded clay, expanded shale, foamed slag, and clay brick chippings. I n cer­ tain applications it is also possi ble to find wood wool, wood chips and plastics such as polysty­ rene beads. Normal-weight aggregates According to their average densities, blends of gravel, chippings, ballast, mineral recycling materials and sand are regarded as normal­ weight aggregates. Heavy aggregates Iron ores, lead shot, sulphates and barytes are heavy aggregates that can shield radioactive radiation and are therefore used in the con­ struction of nuclear reactors and x-ray faci l ities. Grading curves The proportions of the various grain sizes in a graded aggregate have a major influence on the material properties. They govern the worka­ bility and compactability of the wet concrete and the quantities of water and binder required. In order to achieve high density and high strength with as little bi nder as possible, con­ crete aggregates to D I N 4226 should form a dense structure of coarse and fine particles and have a small surface area that must be coated by the binder. The smal ler grain sizes are responsible for good workability and com­ pactability. In reinforced concrete the largest grain should be smaller than the clear spacing between the reinforcing bars and between rein­ forcing bars and formwork (concrete cover) so that an adequate covering of binder is always guaranteed. The maximum size of aggregate in reinforced concrete is usually approx. 32 mm, in mortar approx. 4 mm. Standardised grading curves specify the com­ position of the graded aggregate. Graded aggregate is sieved with a standard set of sieves (nine sieves with mesh apertures from 0.25 to 63 mm) . The result allows us to deter­ mine how much (in % by mass) of the total mass of aggregate has passed each sieve and whether the mixture can be i mproved by add­ ing certain grain sizes. Additives/admixtures

Chemical substances may be added to improve the concrete properties during working and in the finished state. Plasticisers ease the placing of the concrete. Accelerators and retarders enable the heat generation d uring setting to be adjusted to the external tempera­ ture (fig. B 49) . Pigments

Metal oxides can be used to produce coloured concrete products. Organic pigments on the

other hand, do not usually remain chemically stable in the cement mixture, and this limits the choice of colours.

Mortar

Mortar is a mixture of binder, water and sand, possibly also additives/admixtures to improve the properties. The constituents are either mixed on site or premixed at the works. As the composition of standardised mortars is more accurate in the works than on the building site, premixed mortars are preferred. We dis­ tinguish between several types of mortar: Ready-mixed mortars are ready-to-use standard mortars of groups 1 1 , I l a and I l l . They contain a retarder that maintains work­ abil ity for up to 36 hours. Premixed "coarse stuff" consists of a mix­ ture of non-hydraulic or hydraulic lime plus aggregates to which water and - depend­ ing on req u i rements - other binders are added on site. Premixed dry mortar is suppl ied in sacks or filled into the silos of on-site batching plants; water is added on site according to the suppl ier's i nstructions. I n on-site batching plants the raw materials are stored separately and then mixed on site with water in a predetermined ratio. Mortar can improve sound and thermal insula­ tion as well as fire protection. Depending on the application, we d istinguish between mor­ tar for masonry, renders and screeds. Mortar for masonry ensures shear- and compression­ resistant joints between the i nd ividual mason­ ry units. Mortar for renders - in the form of a thin, uniform coating - protects walls against the weather and mechanical damage, or forms a substrate for further work (fig . B 4 . 1 1 ) . Mortar for screeds serves as a wearing course or as a backing for the floor covering (see " F loors", p. 1 72 ) . Mortar for masonry

Mortar for masonry is d ivided into normal­ weight mortar ( N M ) , lightwei g ht mortar (LM) and thin-bed mortar (OM) (fig . B 4 . 1 0) . D I N 1 053-1 d ivides normal-weight mortars into a further five groups, distinguished accord ing to their binder and sand content. This leads to corresponding applications. Group I mortars may not be used in, for exam­ ple, walls more than two full storeys high and in walls < 240 mm thick. There are no such restrictions for group II and I l a mortars. Group I I I and I l i a mortars may not be used for the external leaves of double-leaf masonry walls. Lightweight mortars are defined as mortars with an oven-dry density < 1 .5 kg/dm3. If the value is below 1 .0 kg/dm3, the mortar i s c lassed as a thermal insu lation mortar that can be used for masonry with a low thermal transmittance.

Colour

Abbreviation

DeSignation

code Plasticiser

BM

yellow

Superplasticiser

FM

grey

Air enlrainer

LP

blue

Waterproofer

OM

brown red

Retarder

VZ

Accelerator

BE

green

G routing aid

EH

white

Stabiliser

ST

violet B 4.9

Min. 28-day compress. strength

Mortar for masonry, DIN 1 053 group

Suitability test IN/ mm>]

Quality test IN / mm>]

Min. adhesive shear strength

IN / mm>]

Normal,weight mortar I 3.5

2.5

0.1

7

5

0.2

III

14

10

0.25

ilia

25

20

0.3

7

5

0.2

14

10

0.5

lIa

Lightweight mortar LM 2 1 ; LM 36 Thin·bed mortar

B 4. 1 0

Type of mortar Mortar for render, DIN V 1 8550 class P I

P II

a

Non·hydraulic lime mortar

b

Hydraulic lime mortar

c

Mortar with hydraulic lime

a

Min. 28-day compressive strength, quality test

Mortar with masonry lime

2.5

or mortar with render & masonry binder

P ili

b

Lime cement mortar

a

Cement mortar with

10

lime hydrate b P IV

PV

Cement mortar

a

Gypsum mortar

b

Gypsum sand mortar

c

Gypsum lime mortar

d

Lime gypsum mortar

a

Anhydrite mortar

b

Anhydrite lime mortar

2

2

B 4. 1 1

B 4.5

Structural shell, bus terminal, Casar de Caceres, Spain, 2003, Justo Garcia Rubio

B 4.6 B 4.7

Physical parameters of mineral binders Reinforced concrete structure with artistic use of joints and formwork, Stadelhofen railway station, Zurich, Switzerland, 1 990, Santiago Calatrava

B 4.8

B

4.9

Villa Savoye, Poissy, France, 1 929, Le Corbusier Designation of concrete additives/admixtures to D I N E N 934-2

B 4 . 1 0 Mortar for masonry, D I N 1 053 groups B 4. 1 1 Mortar for render, D I N V 1 8 550 groups

57

Building materials with mineral binders

Compressive strength class for normalweight concrete

Compressive strength classes to EC2 '

Normal-weight concrete

C12/15

Compressive strength, characteristic value '

Compressive strength, mean value

Tensile strength, mean value

IN / mm"]

IN/mm"]

IN / mm"]

IN / mm"]

12

20

1 .6

26 000 27 500

Modulus of elasticity

C 1 6/20

16

24

1 .9

C20/25

20

28

22

29000

C25/30

25

33

2.6

30500

C30/37

30

38

2.9

32 000

C35/45

35

43

3.2

33500

C40/50

40

48

3.5

35 000

C45/55

45

53

3.8

36000

C50/60

50

58

4.1

37 000

1 The characteristic compressive strength corresponds to the strength of a cylinder, 1 50 mm dia. x 300 mm long,

28 d old, the second value to the strength of a cube, 1 50 x 1 50 x 1 50 mm side length, 28 days old.

Thin-bed mortars with aggregates < 1 mm are suitable for masonry with bed joints and per­ pends < 3 mm. The low proportion of joints results in a lower thermal transmittance through the wal l .

Concrete

These days, concrete is produced with a high q uality and used for a multitude of different applications. The architectural options extend from mechanical surface treatment to printing to the use of special types of cement, e . g . white concrete (fi g . B 4. 1 4). Tadao Ando is a proponent of the aesthetic use of fair-face con­ crete, wel l known for his skilful use of surface treatments and the arrangement of formwork ties as a design element (fi g . B 4 . 1 2) . Mixtures of cement, aggregates a n d water harden to form a man-made stone - concrete. Accord ing to the density of the aggregates, we class concrete as normal-weight, lightweight or heavy. The aggregates, cement and additives/ admixtures determine the properties of the con­ crete. As a rule, 1 m3 of normal-weight (wet) concrete comprises 2000 kg gravel, 250-400 kg cement plus 1 50 kg water. Production

Concrete components can be cast on site (in situ concrete) or prefabricated off site and then transported to the building site (precast con­ crete). Formwork Wet concrete ( i . e . stil l workable) can be mould­ ed i nto virtually any shape. The formwork acts as the mou ld and is usually made from timber or wood-based products. I n the case of larger components the timber formwork is supported by steel props and frames. Threaded fasteners (formwork ties) pass through the component, e . g . a wal l , and d i stribute the pressure of the wet concrete. This leaves holes in the concrete after the formwork has been struck and these holes are a typical feature of fair-face concrete surfaces, just like the material and surface tex­ ture of the formwork. The striking times for B 4. 1 5

58

B 4.13

formwork are standardised depending o n the type of component and the strength of the cement. Placing and compacting Normally, the concrete is placed in the form­ work with the help of hoses and pumps. Once in position, it is compacted with vibrating plant and other equipment in order to minimise the air content, create a good surface finish and generate a structural bond with the steel rein­ forcement. Self-compacting concrete The use of self-compacting concrete (SCC) is growing. The consistency of this concrete ena­ bles it to be placed in the formwork without the need for any additional mechanical compact­ ing measures. The fluid consistency is achieved by adding plasticisers. Self-compact­ ing concrete is ideal for fair-face concrete and components with complex geometry. However, there is sti l l no standard covering loadbearing components made from this material . Curing The temperature and humidity of the air influ­ ence the hardening process and the properties of the concrete. Concrete components must therefore be properly cured for at least seven days after pourin g . In order to prevent prema­ ture drying-out, concrete is therefore left in the formwork and surfaces are covered with sheet­ ing or sprayed with water or a curing agent. The striking times depend on the dimensions of the component and the strength class of the concrete. Reinforcement Concrete has a low tensile strength but a high compressive strength (fi g . B 4 . 1 3) . Providing reinforcement in the form of steel meshes and/ or bars creates a composite material which, due to the bond between the steel and the hardened cement, achieves high tensile and compressive strengths. The steel reinforcement also prevents excessive shrinkage cracking.

Building materials with mineral binders

B 4.12 Formwork tie holes left exposed in finished con­ crete wall, Koshino House, Japan, 1 984, Tadao Ando B 4.13 Compressive strength classes for normal-weight concrete to EC 2 B 4.14 White cement, white stone dust and white pig­ ments, Office of the Federal Chancellor, Berlin, Germany, 2001 , Axel Schultes B 4.15 Porous drainage boards laid in the formwork, holi­ day home near Flums, Switzerland, 2003, EM2N B 4.16 Physical parameters of concrete in relation to the aggregate B 4.17 Masonry units (cement binder + natural aggre­ gate) , New Synagogue, Dresden, Germany, 2001 , Wandel Hoefer Lorch + Hirsch

Concrete with various aggregates

Density

Modulus Compress. of elasticity strength

[kg m"l

[N/mm']

[N/mm']

1 300 1 800 5000 6500

1 .5 4.2 13 15

[kJ/kgK)

Heat storage index [kJ/ m3K)

0.10 0.21 0.55 0.65

1 .4 1 1 .30 1.10 1 .08

990 1 1 02 1 435 1 560

0.29 0.32 0.41 0.65

1 .52 1 .79 1 .92 2.10

1 553 2099 2495 2990

Thermal Heatconductivity capacity [W/mK)

Lightweight wood particle concrete

60% 43% 1 5% 11%

700 850 1 300 1 450

by vol. wood by vol. wood by vol. wood by vol. wood

Lightweight wood particle concrete

37% by vol. wood. 2 7 % b y vol. wood, 26% by vol. wood, 20% by vol. wood, 1

1 3% 30% 37% 48%

by vol. PCM by vol. PCM by vol. PCM by vol. PCM

+

phase-change material (PCM) ,

1 025 1 1 75 1 300 1 425

1 600 2200 3533 4433

4.1 6.2 1 2.2 15

PCMs are latent heat storage media that can absorb thermal energy over a certain range without a rise in tempera­ ture. This is achieved through a phase transition from solid to liquid. B 4. 1 6

Concrete cover The strongly alkali ne composition of the con­ crete protects the reinforcement against corro­ sion. However, over time carbon dioxide or chlorides from the surroundings (e.g. sea salt or de-icing salt) can penetrate the surface and together with moisture bring about chemical neutralisation of the outer layers of the concrete. In order to prevent such substances reaching and corroding the reinforcement, D I N 1 045 specifies minimum dimensions for the concrete cover. If these dimensions are not adhered to, the reinforcement may corrode , which leads to an increase in volume and to spal l i n g of the concrete. Important factors influencing the con­ crete cover are the exposure conditions and the diameter of the reinforcing bars.

crete). A new development is translucent con­ crete in which light-carrying fibres (e. g . g lass fibres) are used as an aggregate (see "The architect as building materials scout", p. 1 7) . Environmental compatability

The lion's share of the primary energy required for the production of concrete goes into the manufacture of the cement clinker. In order to avoid transportin g ready-mixed concrete over long d i stances, it is usual to set up a batching plant on large building sites. H i g h-qual ity con­ crete leads to more slender components and so the greater effort during construction is offset by lower consumption of materials and a longer service life. Recycling

Quality control Quality control measures guarantee the quality of the concrete during all operations because deviations from the standardised processes would mean that the concrete can no longer comply with the design requirements. For example, the concrete mix and its compressive strength are checked using test cubes prior to construction, and the production i s monitored constantly. Placing and curing of the concrete must be recorded accurately by the site staff responsible. Special types of concrete

In principle, concrete from demolished buildings can be reused for new concrete components. Up until now pieces from building debris have been mainly used in roadbuilding and for filling work, i.e. for low-grade operations ("downcyc­ l i n g " ) . It is already possi ble to examine the qual­ ity of the scrap material, however, and thus create the regulatory framework for the reuse of concrete as aggregate. But owing to its angular form and grading curve, concrete mixes with this aggregate require a h igher cement content. This nullifies the advantages of recycl i ng because the cement production is associated with a high energy i nput.

Properties and applications

Concrete is i ncombustible (building materials class A 1 ) and resistant to many aggressive substances. By choosing the right the mix, concrete can be made resistant to de-icing salts, impervious to water or gastight. Plain concrete components Concrete components without reinforcement are suitable for numerous applications:

External works: e . g . slabs and pavings, kerb­ stones, concrete blocks for embankments Services and shafts: waste water pipes, inspection chambers Floors: filler blocks for floor slabs Roof coverings: concrete roof tiles, available in similar formats to clay roof tiles, but also in large formats I nternal fitting-out: concrete blocks for walls, reconstituted stone blocks, floor finishes, stair treads Reinforced concrete components Loadbearing assemblies can be prefabricated from columns and beams in any form, e.g. to match the bendi n g moment d iagram. At the precasting yard formwork with multiple reuses can be worthwhile, especially in the case of components with complex geometry. Stair flights are frequently made from precast con­ crete. Precast concrete planks are precast with

The use of fibres made from g lass, synthetic materials, steel or carbon can further alter the properties of the concrete, e . g . increase the tensile strength, improve the i mpact toughness, reduce cracking. The addition of organic or inorganic fibres increases the strength of concrete. Fibre-rein­ forced components are more durable and can have more slender dimensions than those made from normal-weight concrete. Aggregates made from wood reduce the thermal conductiv­ ity and increase the specific heat capacity (fig. B 4.1 6) . Textiles can accommodate tension stresses and are not at risk of corrosion. They can be used to reinforce concrete with a small concrete cover and hence result in smaller and lighter concrete components (textile-reinforced con-

59

Building materials with mineral binders

tension reinforcement and then completed on site with a concrete topp i n g . Cavity facade designs can be erected with a facing leaf of precast concrete panels.

M ineral-bonded components

Mineral-bonded components exhibit high dimen­ sional accuracy because their manufacturing process using steam and pressure at a temper­ ature of 1 60-220°C minimises their shrinkage characteristics. They can be produced in vari­ ous sizes, densities and compressive strengths, with or without holes (fi g . B 4.20) . Lightweight concrete blocks

By using aggregates such as pumice or expanded clay, concrete works can produce a wide range of bricks and blocks for internal and external walls. Such components are char­ acterised by a low thermal conductivity. Aerated concrete blocks

d

B 4. 1 8

Aerated concrete consists of cement with fine­ grain substances such as quartz sand, fly ash and a blowin g agent. The production in an autoclave (high pressure plus high tempera­ tures of about 200°C) is only possible in a con­ crete works. The resultin g concrete contains up to 80% voids, which means a low density cou­ pled with good strength , plus good sound insu­ lation and fire protection characteristics. Masonry units and large-format panels for load­ bearing and non-load bearing walls can be pro­ duced from aerated concrete. Granulated slag aggregate units

These masonry units are made from granulated blast-furnace slag plus cement or lime as a binder. After mou l d i n g they are hardened in steam or gases containing carbonic acid . Granulated slag aggregate units exh ibit similar properties to calcium silicate bricks and blocks and are used for similar purposes. However, they have a lower thermal conductivity for the same density. As an alternative to concrete blocks, the curing of which is time-consuming and costly, the building industry has developed methods in which mineral binders are cured by steam. Automatic presses are used to produce, for example, masonry units, in economic formats with a high degree of dimensional stability. B 4 . 1 8 Mineral-bonded boards a Plasterboard type A b Flooring-grade board c Fibrous plasterboard d Cement fibreboard B 4 . 1 9 Type designations of gypsum plasterboards: comparison of EN 520 and D I N 1 8 1 80 B 4.20 Physical parameters of mineral-bonded masonry units B 4.21 Interior design with gypsum plasterboards, office building, Stockholm, Sweden, 1 997, Claessen Koivisto Runee B 4.22 Facade of cement fibreboards, warehouse, Laufen, Switzerland, 1 991 , Jacques Herzog & Pierre de Meuron

60

Calcium silicate units

Calcium silicate is a mixture of lime and sand that sol idifies upon slaking with water. I nitially, lime is the binder in the resulting mass, but fur­ ther heating in steam causes the lime hydrate to react with the sand particles to form hydrat­ ed calcium silicate. Bricks and blocks made from this material can be manufactured with very tight tolerances and achieve a high com­ pressive strength. Calcium silicate units are frost-resistant and suitable for facing masonry both internally and externally.

Mineral-bonded boards

Plasterboards

The rapid curing time of gypsum enables the cost-effective manufacture of a number of products, especially large-format boards for walls, floors and ceilings. Plasterboards are produced as an endless strip and laminated with cardboard both sides, which also encloses the two long edges. The lamination serves as reinforcement, accommodating tensile forces and enabl i n g longer spans. Plasterboards can be worked easily with simple tools, e.g. sawn, cut, drilled or routed. They can be fixed to metal or timber frameworks with screws or nails, to a m ineral substrate by bond­ ing with dabs of mortar. The main advantages of plasterboards are their low weight, good strength and low thermal conductivity. This material has a high proportion of macropores, which help to regulate the interior humidity. At high humidities they absorb moisture, and release it again when the air is drier. Further­ more, aggregates and fillers influence the material properties. Untreated plasterboards are vulnerable to the effects of water. Addition­ al protection can be provided by claddings, coatings or plaster. Plasterboards are also used as a cladding for fire protection purposes. The duration of fire resistance depends on the additives and the thickness. Types of plasterboard Gypsum plasterboards are ideal for internal use on horizontal and vertical surfaces. The type designations are given in D I N EN 520, which has replaced D I N 1 8 1 80 (which, how­ ever, is stil l valid until August 2006) . Capital letters indicate the performance features, which may also be combined. The following examples are supplemented by fig . B 4 . 1 9:

Type A deSignates standard boards whose good face forms a backin g for gypsum plas­ ter or coatings. Type F designates boards with a defined fire resistance; the gypsum core usually contains mineral fibres. Type H deSignates boards with a lower water absorption; these boards can be used in wet rooms . Plasterboards c a n be supplied in thicknesses from 9.5 to 25 mm. For production reasons the standard width of the boards is 1 250 mm, but 600 mm for boards 25 mm thick. The boards may measure up to 4000 mm lon g . Plaster­ boards must be stamped with EN number, manufacturer's name, date and type designa­ tion. Plasterboards can be further processed in the works and provided with holes or slots to suit particular applications. Gypsum wallboards Gypsum wall boards consist of gypsum to which inorganic fillers or fibres can be added.

Building materials with mineral binders

They have smooth, flat surfaces. To i ncrease their stability they are usually produced with tongue and groove connections on the edges. Gypsum wall boards can be used to construct lightweight, non-Ioadbearing walls (see "Walls" , p. 1 56) . The thickness varies between 50 and 1 50 mm. These boards are ideal for fire-resist­ ant walls. Ceiling boards The (usually) square ceiling boards are avail­ able for satisfying fire protection requirements, for sound insulation and as decorative ele­ ments. The numerous perforation patterns available open up a wide choice of surface and design options with different acoustic effects. Composite boards Boards for floors, walls and cei lings can be provided with plasterboard surfaces that are already bonded to an insulating material such as polystyrene or mineral-fibre sheets. (see "Floors", p. 1 74 ) . Fibrous plasterboards

Fibrous plasterboards consist of a mixture of gypsum and cellulose fibres. The fibres act l ike reinforcement and increase the strength of the board. Fibrous plasterboards can be obtained with larger cross-sections than plasterboards and in building materials classes A 2 and A 2 to DIN 4 1 02-1 . Two or three layers of fibrous plas­ terboards may be bonded together as an alter­ native to a cement screed. Mineral-bonded particleboards Mineral-bonded particle boards consist of approx. 25% by mass wood chips and 65% organic binders (Portland cement, gypsum, magnesia) plus additives. To form these boards the constituents are mixed with water, spread out and compacted under high pres­ sure. Mineral-bonded particle boards are suita­ ble for floors, walls and soffits internally or externally depending on the type of binder used.

Plasterboards to DIN 1 81 80 (valid until August 2006)

Plasterboards to DIN EN 520

Plasterboard

type A

Plasterboard with defined density

type 0

GKB

Plasterboard

Plasterboard for cladding

type E

Plasterboard with improved microstructure bonding of core at high temperatures

type F

GKF GKFi

Fire-resistant plasterboard Fire-resistant plasterboard, impregnated

GKBi

Plasterboard, impregnated

GKP

Plasterboard for plaster background

Plasterboard with reduced water absorption

type H

Plasterboard with enhanced surface hardness

type I

Board for plaster background

type P

Plasterboard with enhanced strength

type R B 4. 1 9

Type of masonry unit

Abbreviation

Density classes available [kg / dm"J

Compressive strength classes available [N / mm']

Calcium silicate

solid (high-precision) perforated and hollow (high-precision) tongue and groove system fair faced brick veneer brick

KS, KS (P) KS L, KS L(P) KS-R, KS-R (P) , KS L-R, KS L-R (P) KS Vm, KS VmL KSVb, KSVb L

1 .6-2 .2 0.6-1 .6 0.6-1 .6

4-60 4-60 4-60

1 .0-2.2 1 .0-2 .2

1 2-60 20-60

Aerated concrete

0.3-0.5 0.5-0.8 0.65-0.8 0.8-0.0 0.35- 1 .0

2 4 6 8

Hbl V, Vbl, Vbl S VbI S-W

0.5-1 .4 0.5-2.0 0.5-0.8

2-8 2-1 2 2-1 2

Hbn Vbn, Vn Vm, Vmb

0.9-2.0 1 . 4-2. 4 1 .6-2.4

2-1 2 4-28 6-48

HSV HSL HHbl

1 .6-2.0 1 .2-1 .6 1 .0-1 .6

1 2-28 6-12 6-12

standard, high-precision

PB, PP

panel, high-precision panel

Ppl, PPpl

Lightweight concrete

hollow panel solid, solid with slits solid with slits and special thermal insulation properties Concrete

hollow solid facing Granulated blast-furnace slag

solid perforated hollow

Cement fibreboards

Cement fibreboards are produced from syn­ thetic and cellulose fibres, cement and water (figs B 4. 1 8 d and B 4.22 ) . They are weather­ proof, impervious to water and incombusti ble. They are available i n thicknesses from 8 to 20 mm and in sizes up to max. 1 500 x 3100 m m .

B 4.20

Perlite wallboards

Perlite wallboards have a core of cement-bond­ ed l ightweight perlite aggregate. A glass cloth plus a layer of cement on each side protect the approx. 1 1 mm thick core. These incombustible (building materials class A 1 ) , extremely robust boards are suitable for use as a render back­ ground on facades.

B 4.22 61

Bitu m i nous materials

B 5. 1

Organic sediments on the seabed and the associated carbon enrichment formed the basis for the formation of deposits of petrole­ um, natural asphalt and bitumen. High temper­ atures and pressures over m i l l ions of years transformed these substances into petroleum. I n natural deposits bitumen frequently occurs together with fine mineral inclusions in the form of natural asphalt. In the period around 3000 BC bitumen was used in Mesopotamia instead of loam as a mor­ tar for masonry. In road building asphalt was used in conjunction with clay bricks in ancient times to form highways. The Hanging Gardens of Babylon were waterproofed with layers of natural asphalt tiles, clay bricks and mortar (fi g . B 5 . 4 ) . This style of rooftop garden was popular around the Mediterranean at the time of the Renaissance, and these gardens req u i red bitu­ men to seal them.

·

Pure bitumen is worked at temperatures of 1 50220°C. After cooling, the bitumen fulfi ls its func­ tion immediately, e . g . as a seal or an adhesive. When cold, bitumen can only be used in a solution or dispersion: •

•

•

Commercially produced bitumen and

(hard paving-grade bitumen) , the residue left behind when further su bstances are volatised from straight-run bitumen by heating in a vacuum with the simultneous addition of steam. Blown bitumen is produced by blowing air and oils into molten straight-run bitumen; it exhibits greater elasticity.

A bitumen solution is made up of bitumen plus a petroleum disti llate (e.g. petrol), which undergo a curing process. A bitumen emulsion consists of a mixture of bitumen, water and an emulsifying agent; the emulsion dries slowly as the water evapo­ rates. Fillers are added to solutions and dispersions to form fi l l i n g compounds.

bitumen products

Properties

B B B B

5 . 1 Liquid bitumen 5.2 Systematic classification of bituminous binders 5.3 Physical properties of bitumen 5.4 The Hanging Gardens of Babylon, one of the first structures waterproofed with bitumen, 562 BC B 5.5 Flat roofs as an expression of technical progress, Weissenhof Estate, Stuttgart, Germany, 1 927, Ludwig Mies van der Rohe

62

The spread of the flat roof across Central Europe d uring the 1 9th century was encour­ aged by the invention of reinforced concrete and the development of framed buildings, which permitted large spans and flat roofs capable of carrying heavy loads. However, the at best only very shallow roof pitches meant that such roofs had to be sealed against the ingress of rainwater. This was achieved with a combination of bitumen and layers of paper on pressed cork boards. By the middle of the 1 9th century the industrial refining of petroleum had covered the increased demand for bitumen. I n order to obtain paraffin for lamps, refineries were establ ished, initially in America, in which petroleum was broken down through d istillation into its components with their different boiling points. One non-distil lable residue was bitu­ men, which today is sti l l obtained in the same way. We d istinguish between the following types of bitumen: Straight-run bitumen (soft bitumen) represents the non-vapourising residue. . Various grades of vacuum asphaltic bitumen •

Bitumen consists of d ifferent mixtures of vari­ ous hydrocarbons and hydrocarbon derivatives depending on the geographical location of the petroleum deposit from which it is obtained. Nevertheless, the useful properties are almost identical. They depend on the so-called colloi­ dal system - the q uantitative composition of malthenes (dispersion agent and soluble, melt­ able petroleum resins) and asphaltenes (insolu­ ble, non-meltable constituents). This results in the physical properties so typical of bitumen : a rise in temperature makes bitumen gradually softer, but the process is reversible and similar to that of a thermoplastic material. Bitumen exhi b its viscoelastic properties that range from elastic deformation to fluid ity depending on the temperature. Polymers mixed into straight-run bitumen can i nfluence these properties (poly­ mer-modified bitumen, PmB) . Bitumen has the function of a b inder. When hot and runny it wets fibres, metals and mineral materials very well and bonds them together after cooli n g . However, the action of oxygen i n the a i r a n d ultraviolet rad iation can make bitu-

Bituminous materials

Bituminous binders

Bitumen in natural asphalt

Tar and binders containing tar

Bitumen and derivatives

Rapid-curing cutback

Special bitumen

Fluxed bitumen

emulsion Cationic bitumen emulsion Polymer-modified bitumen emulsion B 5.2

men brittle on the surface and impair its adhe­ sive qual ities. Bitumen products should there­ fore be protected agai nst ultraviolet radiation by covering them in some way (e. g . chippings on flat roofs) . At room temperature bitumen exhi b its a high resistance to salts, weak acids and also strong alkalis. The d istillation of petroleum represents a physical method of production. Bitumen is non-hazardous in b iological terms and can also be used as a sealant in drinking water appl ica­ tions. Depending on its degree of purity, it can also be reprocessed and recycled. Bitumen should not be confused with pitch or tar, which have a similar appearance. Tar is obtained through the thermal cracking of coal a chemical process. These pyrolysis products contain polycyclic aromatic hydrocarbons (PAH) , and as these are carcinogenic, prod­ ucts made from pitch or tar are hardly ever used these days.

Bitumen

Paving-grade bitumen

Bitumen for use in asphalt for roadbuilding rep­ resents the largest market for bitumen. Various grades of straight-run bitumen are suitable as a b inder for minerals. The minerals used can be natural (e. g . gravel, chippings, bal last, san d ) , man-made ( e . g . slag ) , o r mineral products obtained from recycl i n g processes; their con­ tent is about 95% by weight. The asphalt required for surfaces to roads, landing strips, cycle tracks, etc. is produced in stationary mix­ ing plants. It has to satisfy high quality stand­ ards in terms of affinity to the binder, weather resistance, shock resistance and compressive strength as well as resistance to the effects of heat. The mixing grades for the asphalt are d ivided into two different types depending on the void content of the finished layer, distin­ guished accord ing to their mechanical and working properties: rolled asphalt with a no­ fines porosity (which must be compacted after

Density

Thermal conductivity

Specific heat capacity

Thermal expansion

Water absorption

[kg/m']

[W/mK]

[kJ/kgK]

[mm/mK]

H

Vapour diffusion resistance index [-]

990-1 1 00

0.1 5-0. 1 7

1 .7-1 .9

0.06

< 0. 1 %

approx. 1 00 000

laying), and mastic asphalt with a binder con­ tent greater than that of the voids. Roads usual­ ly comprise three layers: base, binder and sur­ facing. The uppermost layer can be coloured by adding inorganic pigments such as iron oxide (red) or chromium oxide (green) to indi­ cate traffic lanes.

Industrial bitumen

I ndustrial b itumen is the term used for the blown bitumen and solid bitumen used in build­ ing. Applications

The plasticity range can be adjusted by select­ ing a suitable grade of bitumen (fig . B 5.8) , and this makes bitumen ideal for protecting bu ild­ ings and structures thanks to the good bonding and adhesive properties and impermeability with respect to water vapour d iffusion. Depend­ ing on the type of construction to be sealed against i n g ress of water, we d isti nguish between roof and tunnel waterproofing , sealing of rigid or movable joints, and the sealing of tanks, basements or swimming pools. The following bituminous materials are used in building works: Sealing materials bitumen sheeting (with fleece) flexible polymer-modified bitumen sheeting ·

B

5.3

·

Roof coverings bitumen sheetin g (with fleece) corrugated bitumen sheeting asphalt shing les and tiles • •

•

Protective products undercoat (applied cold) topcoat (applied hot) adhesive compounds (applied hot) filling compounds (applied hot/cold) · ·

·

•

Coatings mastic asphalt mastic asphalt flooring asphalt tiles/blocks •

• ·

B 5. 4 63

Bituminous materials

Flexible bitumen sheeting

made from blown bitumen

Bitumen roofing felt with glass fleece base

Bitumen sheeting for waterproofing of roofs

made from polymer-modified bitumen

Bitumen waterproof sheet­ ing for felt torching

R 500 (uncoated felt 500 g/m2)

G 200 DD (glass cloth 200 g/m2)

V 50 8 4 (glass fleece 50 g/m2)

V 13 (glass fleece 50 g/m2)

PV 200 DD (polyester fleece 200 g/m2)

G 200 8 4 (glass cloth 200 g/m2)

Polymer-modified bitumen waterproof sheeting for felt torching

sheeting

G 200 8 5 (glass cloth 200 g/m2) PV 200 8 5 (polyester fleece 200 g/m2)

Insulation bituminised felt bituminised cork felt •

•

Seals jointing compounds •

Flexible waterproof sheeting made from bitumen

Flexible waterproof sheeting made from bitumen is used for sealing structures and roofs (fig. B 5.6). Such products are intended to protect struc­ tures or components against the in- g ress of water and aqueous solutions. The water in these cases occurs in various forms and has different effects, which are explained in DIN 1 8 1 95 (see "Insulating and sealing", p. 1 44).

PYE-G 200 DD (glass cloth 200 g /m2)

PYE-G 200 8 4 (glass cloth 200 g /m2)

PYP-G 200 8 4 (glass cloth 200 g/m2)

PYE-PV 200 DD (polyester fleece 200 g/m2)

PYE-G 200 8 5 (glass cloth 200 g/m2)

PYP-G 200 8 5 (glass cloth 200 g/m2)

PYE-PV 200 8 5 (polyester fleece 200 g/m2)

PYP-PV 200 8 5 (polyester fleece 200 g /m2)

Appropriate i nlays determine the mechanical properties such as strength, extensibil ity and tear resistance. G lass fleece (code letter V) is su itable for low loads, but glass cloth (G) and polyester fleece (PV) are used for h igher loads, less often jute (J) or uncoated felt (R). Metal foil (e.g. copper, aluminium) is used as an i nlay to create a vapour barrier, to prevent root penetration and also below loose soi l . Q uartz sand o r slate granules provide some protection for the flexible sheeting, talcum pow­ der and thin separating layers of polyethylene or polypropylene film ease the rolling/unrolling and working of the sheeting. Flexible sheeting made from blown bitumen has a lower resistance to ultraviolet radiation and therefore req u i res additional protection, e . g . in the form of a layer of loose gravel on flat roofs.

Flexible bitumen sheeting

Flexible bitumen sheeting consists of a backing layer (base) that is soaked in straig ht-run bitu­ men and coated both sides with a facing layer of blown bitumen. The two facing layers are responsible for the waterproofing effect and durability of the flexible sheeting.

B 5.7 64

Flexible polymer-modified bitumen sheeting

In this type of flexible sheeting the facing layers and the bitumen in which the base and inlays are soaked consist of straight-run b itumen to which a thermoplastic or elastomeric material has been added (fi g . B 5 . 7 ) . Both the thermoplastic a n d the elastomeric modification of bitumen results in a flexible sheeting with high thermal stability, good cold­ working properties and better ageing resist­ ance. The guidelines for flat roof construction do not call for a heavyweight surface protection in the form of gravel. The bitumen used for flexible polymer-modified bitumen sheeting is modified with a thermo­ plastic elastomer (styrene-butadiene-styrene, SBS) and has the code PYE. It req u i res protec­ tion against u ltraviolet radiation in the form of chippings. The bitumen in polymer-modified bitumen built­ up felt can also be modified with a thermoplas­ tic material (atactic polypropylene, aPP) - code PYP. Chippings to protect against ultraviolet

B 5.5

radiation are not required for this type of flexi­ ble sheeting. Properties

As two or more layers are employed, flexible bitumen sheetin g is regarded as more resistant to mechanical loads than flexible sheeting made from synthetic materials. However, flexi­ ble bitumen sheeting requires more care and work at junctions and details because no pre­ formed components are available for corners, penetrations and similar details. Ponding on roofs and the associated accumulation of dust and d i rt which can reduce the durabil ity of bituminous flexible sheeting should be avoided by ensurin g a minimum roof pitch of 2°. Types of flexible sheeting

In Germany the d ifferent types of flexible sheeting are distinguished by codes, e.g. PYE­ PV 200 S 5, whose meaning is as follows: •

·

•

type of bitumen used (polymer-modified bitu­ men only) , e . g . PYE type of base with weight in g/m 2 , e . g . PV 200, and in the case of metal inlays the thickness is specified as well type of sheeting and thickness in mm, e.g. S 5

Flexible bitumen sheetin g is used for water­ proofing structures and roofs. The D I N stand­ ards define the following types according to requirements: •

·

•

D I N 52 1 29 Uncoated bitumen-saturated sheeting: R 500 N D I N 52 1 43 Bitumen roofing felt with g lass fleece base: R 500, V 1 3 D I N 52 1 30 Bitumen sheeting for waterproof­ ing of roofs: G 200 DD, PV 200 DD

Bituminous materials

Bitumen grade

Needle penetration [1 / 1 0 mm]

R.a.B. softening point 2 [oC]

Fraass breaking point 3 [oC]

43-37 43-49 54-48 53-59 57-63 55 - 7 1 60-76

-15 -10 -8 -5

40 25 10

85 1 00 1 35

-20 -18 -5

50-90 50-90

48-54 48-55

-15 -15

1

Straight-run bitumen

8220 - 8 1 60 8 1 00 - B70 870- 850 845- 830 B20- 830 825 - 8 1 5 820 - 8 1 0

220-1 60 1 00 - 70 70-50 45-30 20-30 25-1 5 20- 1 0

0 3

Blown bitumen

85/40 1 00/25 1 35 / 1 0 Polymer-modified bitumen

B 5.6 Systematic classification of flexible bitumen sheeting B 5.7 Flexible polymer-modified bitumen sheeting on a substrate coated with bitumen u ndercoat B 5.8 Physical properties of various bitumen grades B 5.9 8itumen u ndercoat as waterproofing to a structure B 5.10 Jointing compound between paving stones

Pm8 65 A Pm8 65 C

elastomer-modified thermoplastic-modified

1

The needle penetration test measures how far a 1 00 g needle penetrates the bitumen (heated to 25°C) in 5 s. The determination of the softening point with ring and ball (R.a.B. method) uses a brass ring filled with bitumen that is loaded with a steel ball and heated in a water or glycerine bath. The softening point is reached when the bitumen has sagged 25.4 mm under the weight of the ball. 3 A layer of bitumen spread evenly on a sheet metal plate is deflected in a defined way. The Fraass breaking point is the temperature at which the layer of bitumen fractures or cracks during bending. 2

B 5.8 ·

·

•

•

•

D I N 52 1 31 Bitumen waterproof sheeting for felt torching: V 60 S 4, G 200 S 4, PV 200 S 5 D I N 52 1 32 Polymer-modified bitumen sheet­ ing for waterproofing of roofs: PYE-G 200 DD, PYE-PV 200 D D D I N 52 1 33 Polymer-modified bitumen water­ proof sheeting for felt torc h i n g : PYE-G 200 S 4, PYE-G 200 S 5 , PYE-PV 200 S 5, PYP-G 200 S 4 , PYP-G 200 S 5 , PYP-PV 200 S 5 DIN 1 8 1 90 Waterproof sheeting for the water­ proofing of buildings: Cu O , 1 D , AI 0,2 D D I N 1 8 1 95-2 Cold-applied self-adhesive sheetin g : KSK

Cold-applied self-adhesive flexible bitumen sheeting has a coating of adhesive on its underside so that it can be laid without the need for any heat (e.g. for supportin g construc­ tions sensitive to heat or on steep pitches) .

Further applications for bitumen

Mastic asphalt

Compared with asphalt for roadbuilding, mastic asphalt has a h igher binder content of sol id bitumen and m inerals with smaller particle sizes. Other materials can be added to modify the properties to suit different applications. Nat­ ural asphalt is frequently added to the bitumen obtained from the refinery, which increases the homogeneity, compactibi lity, deformation resistance and ageing resistance of the mastic asphalt; indeed, the b itumen can be replaced entirely by natural asphalt. As mastic asphalt is free from voids, watertight, resistant to many alkalis and acids and can be laid without joints, it is ideal as a form of waterproofin g , e . g . for wet rooms, for market halls, as protection against substances vulnerable to water, or on monolithic, uninsulated structures.

Bitumen solutions, bitumen emulsions

As undercoats, bitumen solutions and emul­ sions can form the bond between the substrate and flexible bitumen sheeting or insulating materials (fi g . B 5.9) . They form an anchorage in the m ineral substrate and bind any dust on this. Solutions and emulsions are appl ied cold . A s solvents have a low boiling point a n d are therefore volatile and can escape i nto the atmosphere d uring application, it is preferable to use a solvent-free bitumen emulsion or solu­ tion. Jointing compounds

Hot-applied jointing compounds consist of bitumen to which synthetic materials, softeners and m ineral fillers have been added. Joints in concrete, asphalt and paving can be filled with the jointing compound with its elastic or plastic variability (fig . B 5 . 1 0) . Such jointing com­ pounds prevent foreign matter collecting in the joints which m ight impair the movement of the components.

Applications

Flexible bitumen and polymer-modified bitu­ men sheeting is always used in two layers. The first of these can be bonded over the full area or just partially (spot- or strip-bonding) or fixed mechanically, but can even be laid loose. The second layer must be bonded to the first over the full area and with the joints/seams offset. An exception is horizontal waterproofin g in the case of non-hydrostatic pressure, e . g . rising damp, because in this case just one layer of uncoated bitumen-saturated sheeting i s ade­ quate. For details of laying methods and parameters in comparison to flexible sheetin g made from synthetic materials a n d rubber see "The building envelope", p. 1 25-27.

65

Wood and wood-based products

B 6. 1

Wood is readily available throughout the world and can be easily worked with simple tools. It has been used for buildings, everyday objects and furniture since the dawn of civil isation. The use of worked tree trunks in sunken-floor dwellings dating from about 20 000 BC has been proved. The embedded posts at the ends of a roughly 2 x 4 m p it supported the ridge to a couple roof which extended down to the grou n d . In the heavily forested reg ions of Europe, where softwoods grew uniformly, the log construction techniques (fig. B 6.3) stil l used today first appeared around 9000 BC. The spread of settlements to regions with fewer forests led to a more economical form of timber construction - the timber frame. Recognition of the need to protect timber against damage and decay had been taken into account by the Romans, whose perma­ nent timber structures were provided with a stone p l i nth. However, this solution was not familiar to all builders. For example, in the Middle Ages the timber houses of Danzi g (now Gdansk) h a d t o be rebuilt every 20-25 years because the timber in contact with the damp ground began to rot. On the other hand, the stave churches of Nor­ way dating from the 1 1 th to 1 3th centuries i l lustrate the durability of timber structures pro­ tected by careful detail i n g (fi g . B 6.2). Compared to structures of stone, the ind ividual components of a timber building require antici­ patory planning in order to join the individual

parts into a stable overall assembly by means of suitable joints. This is probably one of the reasons why carpenters' guilds were held in such high esteem well into the 1 9th century. I mpressive feats of carpentry such as the oak hammer-beam roof to Westminster Hall (fig. B 6.6) bear witness to their great skills. Industrialisation

Growing marginalisation caused by the new building materials steel and concrete led to efforts to rationalise the production processes and to the development of new forms of timber construction (e.g. platform frame and panel construction) . During the 1 940s Konrad Wachsmann and Waiter Gropius developed the "General Panel System" in America. This system was based on a mod ular arrangement so that walls, floors and roofs could always be assembled in the same way. It was this innovation that made it possible for five unskilled operatives to erect a house ready for its occupants - within just nine hours! Despite a declining market share, timber can still be used for building thanks to the appear­ ance of efficient wood-based products and advancements in structural engineering (fi g . B 6 . 7 ) . And since the mid-1 980s various types of timber claddings have enjoyed a comeback, regardless of the material used for the load bearing structure. The Austrian pro­ vince of Vorarlberg has taken on a pioneering role in contemporary timber architecture - more

B 6.1 Trabocco - vernacular architecture for catching fish, Fossacesia, Italy B 6.2 Stave church, Heddal, Norway, 1 2th century B 6.3 Dairy farm at the foot of the Matterhorn, Wall is, Switzerland B 6.4 The structure of a tree trunk B 6.5 Deformation of solid timber sections depending on their position with respect to the growth rings B 6.6 Westminster Hal l , London, UK, 1 399 B 6.7 Ice rink, Munich, Germany, 1 984, Ackermann + Partner B 6.8 Insurance building, Munich, Germany, 2002, Baumschlager & Eberle B 6.2 66

B 6.3

Wood and wood-based products

Rays H+f Growth ring----P-� Cambium----I-- I Sapwood-----t---- t­ Heartwood----J-H-- tHtl ----

than 20% of all new buildings in that region are built of timber.

W'7-)-1---l-\-+--Ic+-'t-+-'bl---- Pith

1---- 8ark H---- Early wood tt+-1+--- Late wood

8 6.4

· ·

•

Wood as a building material •

Every tree is an individual organism with specif­ ic characteristics. No two pieces of wood are identical. Various criteria influence q uality, appearance and potential applications: • • • •

species of tree location, macrocl imate, microclimate age of tree location within the tree structure (trunk, branch, root, heartwood , sapwood)

•

•

•

Biological structure of wood

More than 30 000 species of wood are known worldwide, and about 500 of these are availa­ ble through the international timber trade. The spectrum of tree species stretches from the eucalyptus of Australia, which reaches a height of 1 35 m, the cypresses with their 1 2 m trunk diameter, to the bristlecone pines of the USA, some of which are 5000 years old. By compari­ son, only a tiny fraction of the species available are used for building in Central Europe; figs B 6.9 and 6 . 1 0 show the most common types. The most important material properties are: •

•

good l ife cycle assessment anisotropy (dependency of most timber properties on d irection of growth) hygroscopy (moisture content is determined by ambient climate) Iow thermal conductivity coupled with good heat storage ability high strength coupled with low weight ( Ioad­ carrying abil ity) multitude of timber species with different appearances (colour, texture, odour) large range of wood and wood-based prod­ ucts available with highly developed methods of working

regenerative raw material carbon dioxide storehouse (reduction in CO 2 concentrations)

8 6.6

The fundamental b u i l d i n g blocks of wood are the cells - wood fibres. It is the job of the cells to transport nutrients, convey water and lend stability to the wood. The majority of cells have an elongated form and lie for the most part par­ allel with the trunk. The rays - running rad ially within the trunk - represent the exception; the rays store organic nutrients (fig . B 6.4) . In terms of evolution, softwoods are older and have a simpler structure, consisting primarily of one type of cell (trache i d ) . Gymnosperm con­ tain more special ised cells with specific tasks. The vessels convey the nutrients and the wood fibres form the load bearing framework for the deciduous Ang iosporm tree. Fig. B 6.4 shows the typical structure of a tree trunk. The cross-section through the trunk in

8 6.7

8 6.5

the majority of trees is as follows (from i nside to outside) : The central p ith is responsible for convey i n g water and storing nutrients in the young shoot, and this part of the trunk dies at a relatively early stage of the tree's growth. I n regions with distinct seasons, the adjoining g rowth rings map the growth of the tree in each year. Every g rowth ring consists of the light-coloured, large-pore early wood (which develops d uring the spring for transporting nutrients) and the dark, denser late wood (which determines the strength of the wood) . The cambium i s responsible for the increase in thickness. It generates wood cells on the inside and the phloem (inner bark) on the out­ side. The p h loem cells form the inner, living part of the bark, which is enclosed by the dead layers of the outer bark. The bark pro­ tects the trunk against drying out and mechan ical damage. Sap wood, heartwood and ripewood species We d ivide timber i nto sapwood, heartwood and ripewood species according to the d iffer­ ent colouration of the cross-section through the trunk. In heartwood species there is a d istinct d iffer­ ence between the colour of the heavy and hard core comprising dead wood cells, which no longer provide any transport functions, and the colour of the sapwood. The wood substances stored in the heartwood (e.g. tan­ ning agents and pigments) provide defence

8 6.8 67

Wood and wood-based products

against fung i and insects that feed on wood. Owing to its natural durability, the use of heartwood obviates the need for chemical preservatives. This group includes oak, Scots pine, chestnut and larch. The ripewood species have, l i ke sapwood, a light-coloured core and do not exh i b it any differences in colour over the trunk cross-sec­ tion . However, the core is considera b ly drier and its properties tend to resemble those of the heartwood species. The ripewood spe­ cies include beech, spruce, fir and lime.

ness or suitabil ity for impregnation can be derived from this. The density is determi ned taking i nto account the moisture content (mass and vol ume changes due to swel l i n g and shrinkage) plus the position of the wood within the trunk. The mean density for softwoods used for load­ bearing purposes l ies between 450 and 600 kg 1m3. However, this can reach 700 kg / m3 among some European hardwoods and even 1 000 kg / m3 for hardwoods imported from over­ seas.

Anisotropy A substance is designated anisotropic (Greek: anisos unequal + tropos turn) when its properties vary with direction. G lass and metal, for example, are isotropic - they exhibit the same properties in all directions. The ani sot­ ropy of wood is due to the wood fibres that run parallel to the direction of g rowth of trunk and branches, and is revealed in the various sections through the wood (transverse, radial and tangential) (fi g . B 6.4) . For example, the swelling and shrinkage of spruce in the tan­ gential d i rection is more than 25 times greater than that in the longitudinal d i rection . The permissible stresses are also considerably influenced by the grain direction. For exam­ ple, spruce can accommodate tensile stress­ es of up to 1 0 N / m m2 parallel to the grain , but perpendicular to the grain only 0.04 N / m m2 (see DIN 1 052) .

Moisture content Wood can absorb a considerable quantity of water within its cellular structure . The moisture content (Um) in the living tree can reach 70% by mass. Among the species of wood that are used for building, the fibre saturation point is reached at Um 30-35%. Above this figure, the cell cavities fi l l with so-called free moisture, but there are practically no more changes in the form d ue to swelling and shrinkage. The mean moisture content of the wood is usually meas­ ured with an electric moisture content instru­ ment. The moisture content is expressed as a mass-based percentage of the water in the wood related to the mass of the wood in the oven-dry condition . According to the new edition of D I N 4074, the moisture content of timber to be i ncorporated i n a building should not exceed 20%. For timber housebuilding the limit is 1 8% , and in g lued components 1 5% . However, t h e absorption o f water takes place not only in liquid form. Due to its hygroscopic nature, wood exchanges moisture with the sur­ rounding air. The so-called equilibrium mois­ ture content is established in timber in use as follows:

=

=

Chemical composition

The main chemical constituents of wood are: • • • •

40-50% cellulose 20-30% hemicellulose 20-30% lignin up to 1 0% other substances and ash

Physical properties

The special physical properties of wood ena­ ble it to be used for a whole range of applica­ tions in the construction industry. However, the proper use of wood presupposes a knowl­ edge about its specific characteristics, suita­ ble species and forms of construction. Density This is understood to be the ratio of the mass to the volume i nc l uding all voids (see "Physi­ cal parameters of mateials", p. 264 ) . Density is one of the most important physical para­ meters of wood because fundamental tech­ nological properties such as strength, hard-

68

• • • •

decreasing moisture content decreasing temperature decreasing grain-load angle i ncreasing density

=

•

With an annual increase of about 7 b i l l ion tonnes, cellulose is the most prolific natural substance on the p lanet. It g uarantees the tensile strength of the wood . Hemicellulose acts as a filler and cement that improves the compressive strength. In contrast to cellulose, lignin is inflexible; it provides the cell walls with the necessary rigidity and compressive strength.

depend on the respective species, the g rowth parameters (density, width of growth rings, pro­ portion of knots), the moisture content, the duration of the load action and the angle between applied load and d i rection of grain . Owing to its anisotropic characteristics, timber parallel to the grain exhibits good structural properties. When subjected to tension, timber generally exhi b its a brittle behaviour, but com­ pressive or flexural stresses usually cause plastic deformations prior to failure. The tensile strength is roughly twice the compressive strength. Generally, the strength of timber increases under the following conditions:

•

· •

heated structures enclosed on all sides 9 ± 3% unheated structures enclosed on all sides 1 2 ± 3% roofed structures open on all sides 1 5 ± 3% constructions exposed to the weather on all sides 1 8 ± 6%

Wood's ability to absorb and release moisture can make a major contribution to improvin g the interior climate. However, the swel l i n g and shrinkage leads to d imensional fluctuations. Fig. B 6.5 shows the deformations of solid tim­ ber sections depending on their position rela­ tive to the growth rings and their original loca­ tion within the cross-section. As far as possi ble, timber components should be incorporated i n a structure with the moisture content to be expected in the final condition long-term. This is a prime req u i rement if chemical preserva­ tives are to be avoided. Strength The strength of a building material is defined as its resistance to fai lure. Timber exhibits a wide range of elastomechanical properties that

A high proportion of knots d isrupts the grain and results in a lower strength. I ndeed, in very knotty Scots p ine the tensile strength can be reduced by up to 85% . The structural proper­ ties also decrease over time in the case of high long-term loads. For example, the bending strength of spruce subjected to a permanent load is only approx. 60% of its short-term strength. As wood exhibits individual character­ istics that experience severe fluctuations, the permissible strength values are set very low for safety reasons. In the end this leads to distinct­ ly oversized cross-sections. The individual load-carrying capacity of a timber member can be determined these days using non-destruc­ tive techniques (see p. 70) , which results in considerably more slender components. Thermal properties The porosity of wood gives it good thermal insulation properties plus pleasant surface tem­ peratures. The thermal conductivity of softwood is about 0 . 1 3 W/mK, that of hardwood about 0.20 W/mK. The thermal conductivity depends on d i rection of grain, density and moisture con­ tent; parallel to the grain it is about twice that perpendicular to the grain. The good specific heat storage capacity of wood ( 1 .67 kJ/kgK for a moisture content of 1 5%) can help to improve the interior c l imate. Compared to many other building materials, the coefficient of thermal expansion is extreme­ ly low. According to D I N 1 052 it is therefore not usually necessary to check changes in length due to temperature fluctuations.

Wood and wood-based products

Species of wood

There exists an enormous diversity of species and each has its own specific serviceabi l ity features, appearance and potential appl ica­ tions. Aesthetic considerations and preserva­ tion aspects must be harmonised when choos­ ing a type of wood. Fig. B 6. 1 1 l ists the properties and features of the timbers used in building. Owing to their faster growth , softwoods are usually more cost­ effective than hardwoods. In recent years more and more softwoods imported from abroad have been used for build i n g . Their advantages over European species are that they are straighter and longer, less vulnerable to rot and have fewer knots. Non-European hardwoods are employed for specific purposes internally and externally, or as exotic, attractive veneers. However, the energy required for their transport considerably worsens their l ife cycle assess­ ments.

a

Tree-felling and the processing of structural solid timber products

Felling trees in winter is advantageous owing to the lower external temperatures, which limits the number of pests, and the reduced risk to the wood outside the sap period. However, the increasing demand for timber means that the winter felling very common in the past is some­ times no longer adequate these days. Depend­ ing on the stock of trees, fast-growing soft­ woods, e . g . spruce and fir, are ready for fel l i n g after 60-1 20 years, oak a n d beech after about 80-1 40 years.

e

Conversion and drying

Various types of conversion - depending on the later use of the wood - are employed to obtain sawn timber from the cross-section of the tree trunk (fig . B 6. 1 3) : •

One-piece conversion The complete retention of the heart (i.e. pith) results in a high risk of crackin g during dry­ ing, and such timber is recommended for low­ grade applications only.

B 6.9 Softwoods (abbreviations to D I N 4076) a Douglas fir (DGA) b Spruce (FI) c Scots pine (KI) d European larch (LA) e Pine (PIP) f Fir (TA) 9 Western hemlock (HEM) h Western red cedar (RCW) B 6. 10 Hardwoods (abbreviations to D I N 4076) a Maple (AH) b Ekki (azobe) (AZO) c Beech (European beech) (BU) d Oak (El) e Dark red meranti (MER) f Merbau (MEB) 9 Robinia (ROB) h Teak (TEK) e

9

h

8 6. 1 0 69

Wood and wood-based products

Species

Density 1

Compr. strength parallel to grain

Tensile strength parallel to grain

Thermal conductivity 2

Heat storage index

Vapour diffusion resistance index 3

[kg/m3]

[N/mm"l

[N/mm"l

[W/mK]

[kJ/m3K]

DGA FI KI LA PIP TA HEM RCW

51 0-580 430-470 51 0-550 540-620 51 0-690 430-480 460-500 360-390

42-68 43-50 55 55 4 1 -58 47 36-55 29-35

82-105 90 1 04 1 07 1 05 84 68 80-93

0.12 0.09-0 . 1 2 0 . 1 2-0. 1 4 0 . 1 1 -0. 1 3 n.a. 0 . 1 0-0. 1 3 n.a. 0.09

AH AZO BU El MER MEB ROB TEK

61 0-660 1 020-1 1 20 700-790 650-760 540-760 81 0-900 740-800 590-700

58-62 87-108 62 65 5 1 -65 59-82 58-72 52-60

82-100 1 50-2 1 5 1 35 90 1 20-165 1 40 1 20-148 117

0. 1 5 n.a. 0.1 5-0. 1 7 0. 1 3-0.21 n.a. n.a. n.a. 0.1 6-0. 1 8

Abbreviation to DIN 4076

Swelling and shrinkage behaviour tangential [% per 1 % change in moisture ct.]

Resistance of heartwood to fungal attack

Resistance of heartwood to insect attack

H

Swelling and shrinkage behaviour radial [% per 1 % change in moisture ct.]

[class 1 -5]

[class 1 -5]

660-750 560-6 1 0 660-720 700-81 0 660-900 560-620 600-650 470-5 1 0

n.a. 88 68 302 n.a. n.a. n.a. n.a.

0.1 5-0. 1 9 0.1 6-0. 1 9 0.1 6-0. 1 9 0.14 0.18 0 . 1 2-0. 1 6 0.1 1 -0. 1 3 0.07-0.09

0.24-0.31 0.29-0.36 0.29-0.36 0.29-0.3 0.29-0.33 0.28-0.35 0.24-0.25 0.20-0.24

3 2 2-3 3 3 2 2 5

3 2 2 4 2-3 2 2 4

790-860 1 330-1460 9 1 0-1 030 850-990 700-990 1 050-1 1 70 960-1040 770-9 1 0

71 n.a. 86 1 40 n.a. n.a. n.a. n.a.

0 . 1 0-0.20 0.30-0.32 0.1 9-0.22 0.1 8-0.22 0. 1 4-0. 1 8 0. 1 3 0.1 7-0.24 0.1 3-0. 1 5

0.22-0.30 0.4 0.38-0.44 0.28-0.35 0.29-0.34 0.26 0.32-0.38 0.24-0.29

1 5

1 5 2 4 3-4 4-5 4 5

Softwoods

Douglas fir Spruce Scots pine European larch Pine Fir Western hemlock Western red cedar Hardwoods

Maple Ekki (azobe) Beech (European) Oak Dark red meranti Merbau Robinia Teak

4 4 5 4 5

1 The

figures here are valid for a mean moisture content of 1 5%. Values for structural timber to EN 1 2524: density 500 kg/m3 0. 1 3; 700 kg/m3 = 0.20; intermediate values may be interpolated. 3 Owing to the numerous dependencies, ARGE Holz (German Timber Organisation) recommends assuming a simplified guide value of 40 for the species of wood given here; EN 1 2524 prescribes the following for structural timber depending on the density: 500 kg/m3 = 20/50; 700 kg/m3 = 50/200. 2

=

B 6. 1 1

. Two-piece spl it-heart conversion This form of conversion reduces the risk of cracking, distortion and twisting. Two- and four-piece conversion, without heart For pieces of timber that must satisfy higher standards of appearance, the heart plank is removed to reduce the risk of cracking even further. •

board req u i res about 1 6 hours to lower the moisture content from 30 to 8%. Grading, surface finishing a n d gluing

Even today, some sawn timber and round tim­ ber sections are allowed to dry in the open air. Depending on the time of year and the prevail­ ing climate, 25 mm spruce boards can take about 60-200 days and the same boards in oak 1 00-300 days to reach a mean moisture content of 20% . The kiln-drying of higher-grade solid timber products takes place under controlled climatic conditions in closed chambers. At a drying temperature of up to 90°C, a 30 mm spruce

The growing conditions and the local c l imate lead to great d ifferences in the structure of wood which are revealed in its properties and its appearance. Strength g rading is prescribed for load bearing and bracing timber members. We distinguish between visual and machine grading. Visual strength grading is based on the external features (e. g . knots, width of growth rings), which permit a conclusion to be reached on the basis of the D I N 4074-1 classification . I n mac h i ne strength g rading the measurement of certain material properties (e.g. modulus of elasticity, density, moisture content) enables higher grading classes to be achieved. Furthermore, there are various criteria for grad­ ing timber according to its aesthetic impres-

a

c

70

b

d

sion. This assessment i s based o n other fea­ tures to those important for strength grading and can be used for non-load bearing members as wel l as an add itional criterion for structural timber. The grad ing required by the authorities is therefore compulsory. As a rule, squared sections, boards and planks are supplied and assembled in the rough-sawn condition. In the case of exposed timber mem­ bers, planed surfaces or special edge work (sharp edge, chamfered) must be contractually agreed beforehand. The gluing of loadbearing sol id timber products (figs B 6. 1 2 c to f) can only be carried out with approved adhesives. Urea-formaldehyde, mod­ ified melamine and phenol-resorcinol resins all contain formaldehyde, but the concentrations lie wel l below permissible limits for this sub-

e

B 6.12

Wood and wood-based products

stance owing to the very small proportion of joints in solid timber products. Adhesives made from polyurethane are free from formaldehyde. The preferred method of achieving structural longitudinal spl ices these days is to use finger joints. Wedge-shaped incisions are made in the end grain of the solid sections to be joined and the pieces are pressed together after spread­ ing adhesive on the joint faces. In glued laminated timber (glulam) the adhesive is spread over the surface of the timber. The use of transparent adhesives and joint thick­ nesses of approx. 0.1 mm result in the i nd ividu­ al laminations of g lulam products being hard ly perceptible. Fissures

Lightning and frost shakes, which occur on the living tree, are not permitted in timber for load­ bearing purposes. By contrast, D I N 4074 expressly permits shrinkage splits that occur during the drying phase. The conversion of the timber, the careful drying and the adaptation of the moisture content during assembly to the climate of the location of use can reduce the likelihood of fissures. However, fissures can never be completely ruled out even with a care­ ful choice of material and correct workmanship.

Wood a n d wood-based products

The industrialisation of the woodworking indus­ try led to the development of many new solid timber products and wood-based products. A selection of the most common solid timber products together with details of their signifi­ cant features is g iven below. Solid timber products

Structural solid timber products involve at most very little change to the structure of the wood. The processing is based - depending on the particular product - on sawing, drying, grad­ ing, finger-jointing and applying adhesive to the surface. Sol i d timber products used for loadbearing or bracing purposes must be approved by the building authorities. Round sections These can be simply trunks with the branches and bark removed (fi g . B 6. 1 2 a) . Relieving grooves are often cut i n larger cross-sections to reduce the risk of uncontrolled crackin g . The surface fin ish can range from retaining the orig­ inal trunk form, to the evening-out of irregulari­ ties, to the machining to size with a constant diameter and smooth surface. Round sections are primarily used for the load bearin g mem­ bers of frames, but also in landscaping work and timber engineering projects. Sawn solid timber made from softwood and hardwood Sawn solid sections (fig. B 6 . 1 2b) are produced by cutting the debarked trunk into square or more usually - rectangular sections. Depend-

ing of the ratio of width (b) to thickness (d) or depth ( h ) , we classify the resulting sections as sawn sections, planks, boards or battens: sawn sections: b $; h $; 3 b and b > 40 mm planks: d > 40 mm and b > 3 d boards: d $; 40 mm and b � 80 mm battens: d $; 40 mm and b < 80 mm •

·

•

•

One-piece conversion

Drying, finger-jointin g , planing, chamfering and further profiling are the operations involved in the processing of sawn sol id timber sections. Such sections are used in many ways in the building industry, e . g . as load bearing mem­ bers, supporting constructions, formwork or external cladding. Solid structural timber (KVH®) These are members made from better-quality sawn softwood products (fi g . B 6. 1 2 c) . The k i l n-drying to a moisture content of 1 5±3%, the careful conversion and the visual strength grading with additional grading req u i rements help ensure a high degree of d i mensional sta­ bility, low risk of fissures and a high-quality sur­ face finish. The trade offers solid structural tim­ ber for exposed and normal purposes. Owin g t o their good d imensional stability, these prod­ ucts are ideal for timber housebuilding and for load bearing members. The low moisture con­ tent enables these products to be used without chemical timber preservatives even in fully i nsulated constructions. Four-piece beams The characteristic feature of the four-piece beam is the central "conduit" running the full length of the timber (fi g . B 6. 1 2 d ) . These prod­ ucts are manufactured by g l u i n g together four softwood squared or similar segments with the grain parallel and the wane placed on the inside. The polyurethane adhesive used forms a structural joint. The moisture content of < 1 5% means that these beams can be used for simi­ lar applications to the sol id structural timber described above. Duo and trio beams These products are made from two or three planks or sawn sections whose surfaces are glued together (fi g . B 6. 1 2 e) . Drying the timber to achieve a moisture content of < 1 5% is fol­ lowed by visual strength grading, finger-joint­ i n g , planing on all sides and cutting to length before the adhesive is appl ied to join the selected pieces to form a beam. Afterwards, the d uo/trio beam can be planed again as a whole and the arrises chamfered. This high­ quality soli d timber product represents another alternative to the aforementioned sol id structur­ al timber and four-piece beam.

Split-heart two-piece conversion

Two-piece conversion, without heart

Four-piece conversion, without heart 8 6. 1 3 8 6. 1 1

Physical parameters of common species of wood 8 6 . 1 2 Solid timber products for structural purposes a Round section b Solid section (VH) c Solid structural timber (KVH®) d Four-piece beam e D uo/trio beam f Glued laminated timber 8 6. 1 3 Forms of conversion 8 6. 1 4 Linear wood-based products a Structural veneer lumber (SVL) b Parallel strand lumber (PSL)

Glued laminated timber (glulam) G l u lam sections consist of at least three soft­ wood boards (laminations) glued together with their grain paral lel. They are manufactured in a similar way to the d uo/trio beams, but in this case the moisture content is only about 1 2% a

b

8 6. 1 4 71

Wood and wood-based products

Wood-based products

Solid timber

Splitting

Debarking LOg S

�1 LI

L__________

Sawing

Sawing

Rotary cutting

Planing

Chipping

I

I

I

I

Sh in g l es __________�

Standard shingles Decorative shingles

ve n ee rs

�1 1

__________� L-

__________� L_____ _ ____ L-

Sawn sections Planks Boards Battens

Solid wood boards

Veneer plywood

Plywood

Laminated veneer lumber

Multi-ply board

Solid structural timber

Blockboard Laminboard

Parallel strand lumber

Four-piece beam

Wood wool

Wood wool slab Multi-ply l ightweight building board

11

11

Chips

Glued laminated timber

Wood cement particleboard

Bitumen-impregnated wood fibre insulating board Wood fibre insulating board Medium board Hardboard

Extruded particleboard

Medium density fi breboard

Tubular particleboard

Plasterboard Fibre-cement board

Oriented strand board Laminated strand lumber

and during the strength grad ing any larger growth-related defects are eliminated. Further­ more, besides straight members it is also possible to produce elements with a variable cross- section, or with single or double curva­ ture. G lued laminated timber is ideal for heavily loaded, long-span members ( e . g . single-storey sheds, bridges) and for components that must satisfy high demands i n terms of dimensional stability and appearance. The life cycle assessment for g lued laminated timber suffers due to the additional energy requirements during production and the use of adhesives. This is also true for other processed timber products. Wood-based products

These products - in the form of fibre boards and particleboards - have been used in the building industry for more than 50 years. In the meantime, the industry has developed a whole range of products (fig. B 6. 1 5) . The appear­ ance of further products capable of accommo­ dating high stresses can be expected in the near future. Wood-based products consist of small pieces of wood, mostly pressed together with the help

of adhesives or mineral b i nders to form boards or l i near members. The raw materials for boards, l i near members, veneers, chips and fibres stem from the sawm i l l , industrial waste and other scrap wood, provided it is free from foreign matter. The production process results in a homogeneity that leads to material properties with a low scatter. In comparison to solid timber products, the anisotropy of the wood is evened out to a large extent, and the swelling and shrinkage tendencies are considerably reduced. Wood-based products made from veneers or boards ( i . e . layered products made up of plies of material) usually achieve higher strengths. Boards made from chips or fibres on the other hand are not as strong as mature timber. If wood-based products are to be used for load­ bearing purposes, then they must be approved by the building authorities. D I N 68 800 parts 2 and 3 d ivide such boards into three classes depending on their resistance to moisture. These classes correspond to conventional usage situations and the anticipated maximum moisture contents that can occur, which may not be exceeded:

Production sizes of wood-based boards

B 6 . 1 5 Systematic classification of solid timber and wood·based products B 6 . 1 6 Formats and material thicknesses of wood·based products (guide only) B 6.1 7 Physical parameters of solid timber products and linear wood· based products B 6 . 1 8 Board·type wood·based products a 3·ply core plywood b Laminated veneer lumber (LVL) C BUilding-grade veneer plywood d BUilding·grade veneer plywood of beech (BFU·BU) e Particle board (P) f Oriented strand board (OSB) g Laminated strand lumber (LSL) h Medium density fibreboard (MDF)

Fibres

Porous softboard

Particleboard

Thin particleboard

Lightweight particle- Gypsum-bonded board with wood particle board wool facing Chipboard with fibre facing

Duo/trio beam

Defibration

Abbre­ viation

·

•

·

B 6. 1 5

HWS class 2 0 : max. moisture content 1 5% (e.g. inner linings to external walls) HWS class 1 00: max. moisture content 1 8% (e.g. cladding to external walls and voids) HWS class 1 00 G: max. moisture content 21 % (e.g. backing layers beneath waterproofing on fl at roofs)

The binder used for wood-based products bonded with synthetic resin can make use of various organic adhesives (urea, melamine, phenol ic and other resins) . Boards of class 1 00 G are impregnated with an approved tim­ ber preservative to combat fungi that feed on wood . Wood-based products bonded with gypsum can be used for applications of class 20 and 1 00, those bonded with cement for class 1 00 G as well (see "Bu i l d i n g materials with m ineral binders", p . 61 ) . Fig . B 6. 1 6 lists the usual material thicknesses and maximum dimensions for common wood­ based products. 3- and 5-ply core plywood

These boards consist of three or five cross­ banded (i.e. adjoining p l ies at 90° to each other) softwood plies (4-50 mm thick) g lued

min. material thickness [mm]

max. material thickness [mm]

max. width [mm]

max. length [mm]

75 75 25 40 280

3000 1 820 1 525 1 850 483

6000 23 000 3000 3050 20 000

Layered products

Multi·ply board Laminated veneer lumber Veneer plywood Building-grade veneer plywood Parallel strand lumber

FSH FU BFU PSL

12 27 8 10 44

LSL OSB P

32 6 2,8

89 40 38

2438 2620 2050

1 0 700 5000 5300

MDF

6

25

1 250

2500

Particleboards

Laminated strand lumber Oriented strand board Chipboard Fibreboards

Medium density fibreboard .

B 6. 1 6 72

Wood and wood-based products

together (fi g . B 6. 1 8 a) . The strengths of such boards vary considerably depending on the respective ply thickness, the species and the quality of the wood. Three- and five-ply core plywood is suitable for load bearing and brac­ ing purposes. Cross-laminated timber Like the three- and five-ply core plywood described above, these boards also consist of cross-banded softwood plies glued together. The individual p lies are glued together to form wall, roof or floor panels with a thickness of up to 85 mm. Computer-controlled assembly plants render possi ble the prefabrication of window and door openings at the works with millimetre precision (figs B 6 . 2 1 and 6.22) . Laminated veneer lumber (LVL) Softwood rotary-cut veneers approx. 3 mm thick can be pressed together and g lued with phenolic resin to form a very efficient wood­ based product (fig. B. 6. 1 8 b) . In grade S (for linear members) the d i rection of grain l ies par­ allel in all pl ies, whereas in grade Q (for planar members) the direction of grain i n some plies lies transverse to the adjoining pl ies.

Structural veneer lumber (SVL) products are linear components with a maximum width of 500 mm that are made from several LVL ele­ ments glued together (fig . B 6. 1 4 a) . These products can be used as beams, columns, facade constructions or in timber housebuild­ ing. Parallel strand lumber (PSL) PSL represents an alternative to solid timber products (e.g. g lued laminated timber) for heavily loaded, linear components (fig. B 6. 1 4 b) . The manufacture o f parallel strand lumber requires strips of rotary-cut veneer 25 mm wide x 0.5-2.6 m long in Douglas fir (OF) or southern yellow pine (SYP) which are aligned with the axis of the beam and g lued together with phe­ nolic resin.

Solid timber products and linear wood-based products

Building-grade veneer plywood (BFU) The term veneer plywood covers boards made from several veneer plies g lued together (fi g . B 6. 1 8 c), but with five p lies or more and thick­ nesses exceeding 1 2 mm the term multiplex is often used. Owin g to their high strength, such boards are ideal for load bearing components. If cross-banded beech veneer i s used instead of softwood (grade B U ) , this produces a very high qual ity, stable board suitable for internal fitting-out and furniture (fi g . B 6. 1 8d ) . Moulded plywood It is also possible to create many different shapes by pressing multi-ply g lued veneer ply­ wood over a negative mould under steam. This technique is mainly used for internal fitting-out and furniture applications. Blackboard (S7) and laminboard (STAE) The core in blockboard and laminboard con­ sists of timber stri ps. In blockboard the strips are 24-30 mm wide, in laminboard < 8 mm. Veneer facings are glued to both sides of the core. In grade 1 even the strips are g lued together without flaws, grade 2 boards can have small flaws here. Particleboards Particleboards are widely used, e . g . as plank­ ing to provide stability, or as a covering to walls and floors. The dense surface is ideal as a backing for veneers and other finishes. We distinguish between particleboards bonded with synthetic resin and those with a mineral binder. The manufacturing process influences the posi­ tion of the chips in the board and hence also the stability of the final product. Pressed parti­ cleboards contain horizontal chips, but i n extruded boards the c h i ps are arranged per­ pend icular to the board.

d

Particleboards (P) consist of relatively small c h i ps lying parallel with the plane of the board and these days are very widely used for inter­ nal fitting-out and furniture (fig . B 6. 1 8 e) . Parti­ cleboards bonded with synthetic resins make use of phenolic, urea or modified melamine resins. Such boards are available in thickness­ es from 2.8 to 38 mm. Vapour diffusion resistance index

Density

Compress. strength parallel to grain

Tensile strength parallel to grain

Tensile bending strength

[kg / m"]

[N / mm']

[N/ mm']

[N / mm']

Swelling and shrinkage behaviour [% per 1 % change in moisture]

420 420 420-460 420-460 420-560

8.5 8.5 8.5-1 1 8.5 8.5 -1 3

7 7-9 7 8.5-13

10 10 1 0-1 3 10 1 1-18

0.24 0.24 0.24 0.24 0.24

40 40 40 40 40

480-550 600-700

16 20

16 18

1 7-20 1 9-21

0.01 /0.32 ' 0.01 /0.32 '

60/80 50/ 1 00

[-]

Solid timber products (e.g. spruce)

Sawn section; S1 0 Solid structural timber (KVH®) Four-piece beam Duoltrio beam Glued laminated timber

7

Linear wood-based products

Laminated veneer lumber grade S Parallel strand lumber (PSL) 1

In the direction of the board parallel to the grain/perpendicular to the grain. B 6. 1 7

h

B 6. 1 8 73

Wood and wood-based products

Board-type wood-based product

Vapour diffusion resistance index

Permissible compressive strength in plane of board 1 [N / m m2]

Thermal conductivity

Shrinkage in plane of board

[kg / m3]

Permissible bending stress perpendicular to plane of board 1 [N / mm2]

[W/ m K]

[% per 1 % change in moisture cont.]

FSH BFU ST, STAE

400-500 400-500 400-800 400-800 450-800

4.4-22 3.5-1 3 1 3-21 13 n.a.

5.5-1 1 7.5-1 1 8-1 9 4-8 n.a.

0.1 4 0.14 0.15 0. 1 5 0. 1 5

0.02 0.02 0.02 0.02 0.02

50/400 50/400 50/400 50/400 50/400

D-s2dO D-s2dO D-s2dO D-s2dO D-s2dO

P OSB LSL

550-700 600-660 670-700

2-4 .5 2.5-8 1 6-20

1 .75-3 1 -4.2 8-1 0

0.13 0. 1 3 0. 1 4

0.035 0.035 0.3-0.4

50/ 1 00 50/ 1 00 50/ 1 00

D-s2dO D-s2dO D-s2dO

MDF HB MBL/MBH SB SB.H/SB.E

450-750 900-1 000 400-900 230-400 200-350

3.6-8.0 6-8 2.5-5 0.8-1 .3 0.8-1 .3

2.8-4.5 4 1 .5-2 . 1

0. 1 -0. 1 7 0. 1 7 0.08-0. 1 7 0.04-0.07 0.056-0.06

0.2 0.2 0.2 n.a. n .a.

8/70 70 8/70 5/10 5/10

D-s2dO D-s2dO E to D-s2dO E E

Abbreviation

Density

Combust2 ibility class

[-]

Layered prpducts

3-ply core plywood 5-ply core plywood Laminated veneer lumber Building-grade veneer plywood Blockboard, laminboard Particleboards

Chipboard Oriented strand board Laminated strand lumber Fibreboards

Medium density fibreboard Hardboard Medium board Porous softboard Bitumen-impregnated woodfibre insul. bd. 1 2

Based on information provided by manufacturers. European combustibility class to DIN EN 1 3501 with the exception of floor coverings. This corresponds to D I N 4 1 02 building materials class B2.

A s the chips of extruded boards are arranged perpendicular to the plane of the board, such boards have high transverse tensile strengths but low tensile bending strengths. Therefore, they are usually installed with planking to both sides (e.g. thin particleboards) . We d istinguish between solid extruded particle­ board (ES) and tubular particleboard (ET) , in which internal longitudinal voids reduce the self-weight of the board . Extruded boards are often used for door leaves or in partitions. Oriented strand board (OS8) Chips (approx. 75 mm long) aligned parallel with the surface of the board give oriented strand board its characteristic appearance (fig . B 6. 1 8 f) , which can remain visi ble as a vigorously textured surface under thin coatings. The edges are vulnerable to damage and OSB is therefore not suitable for exposed areas. Owing to the alig nment of the chips, OSB has a distinctly higher tensile bending strength in the longitudinal d i rection than in the transverse d i rection. This wood-based product is suitable for load-sharing and bracing planking as well as for load bearing flooring beneath a floor covering. Laminated strand lumber (LSL) Chips of poplar approx. 300 mm long are pressed together with the add ition of MDI poly­ urethane adhesive. Laminated strand lumber (fig . B 6 . 1 8 g) exhibits h i g h strengths and is therefore suitable for applications involving high loads. Wood fibreboards Wood fibreboards are manufactured without any b inder - simply by pressing the fine wood fibres together which, owin g to the high pres-

74

sures used, undergo felting (interlockin g ) . The strength of these boards varies depending on the degree of compression. The ensuing fully homogeneous material no longer exhibits any texture (e.g. grain) . In contrast to other wood­ based products, wood fibreboards can be processed like solid timber by routing or similar machining processes to form three-dimensional components. Medium boards (MBLlMBH) and hardboards (HB) are pressed together using the wet proc­ ess without the need for any binder. Their hard­ wearing surfaces protect them against mechanical damage. Owing to their low density and good sound absorption properties, porous fibreboards (SB) and wood fibre insulating boards (WF) are suit­ able for use as combined thermal and sound insulation (see " I nsulating and sealing", p. 1 38) . The manufacture of medium density fibreboard (MDF, fig . B 6. 1 8 h) involves adding a small amount of urea or phenol ic resin to the wood fibres prior to pressi n g . Thanks to their hard , abrasion-resistant surfaces, medium density fibreboards are used as backings for all kinds of finishes and are consequently ideal for i nter­ nal fitting-out. It is also possible to colour the boards evenly by adding pigments; however, the colour range currently available is limited to yellow, red , green , blue and black. These boards can also be shaped with the help of templates under the action of pressure, heat and moisture. Veneers

Almost all the boards and panels made from wood-based products are suitable as backings

B 6. 1 9

for veneer. Consequently, the fitting-out and furniture industries have materials at their dis­ posable that are less vulnerable to shrinkage and cracking than the equivalent solid timber products, but sti l l achieve a simi lar visual effect. This allows more economical usage of high-qual ity species of wood. As traces of wear and damage become readily noticeable along the edges, veneered boards are usually provid­ ed with a solid wood strip to protect the edges. We d istinguish between veneers for plywood, veneers used as backings and those for deco­ rative purposes. Sawn veneers Owing to their production with a circular or gang saw, sawn veneers are at least 1 mm thick, and the high wastage makes them com­ paratively expensive. They can be produced free from fissures and while retaining their natu­ ral colour and grain . Sliced veneers The veneer is sliced lengthwise across the full width of the wood when particularly high-qual ity surfaces are required. The angle of application of the blade influences the final appearance. The wood for this process has to be usually steamed or cooked, which changes the appearance of especially l i ght-coloured wood species such as maple and birch. The use of graded strips of veneer in a mirrored arrangement enables symmetrical veneer pat­ terns or the illusion of greater width. Rotary-cut veneers Rotary-cut veneers are obtai ned by cutting the trunk as it rotates. This creates an endless rib­ bon of veneer material. Rotary-cut veneers are less expensive than sawn and sliced veneers,

Wood and wood-based products

but for most species of wood result in an unnat­ ural, "turbulent" grain. They are used for pro­ ducing laminated veneer lumber or for backing veneers. Rotary-cut face veneers can be obtained from birch, ash and maple provided the trunk is cut at an angle. This results in a similar grain to the sliced veneers but with a greater spacing between the g rowth rings.

Protecting wood

As a regenerative raw material, wood forms part of the natural process of decomposition into its original constituents and their return to the biogenic lifecycle. The purpose of passive and chemical protection of the wood is to guar­ antee the durability of the material and protect the wood against degradation by organisms (fungi and insects) that feed on (and thus destroy) the wood. Fungi extract cellulose and lignin from the wood and therefore cause rot­ ting and decay. They tend to g row when the moisture content exceeds 20% and the cell cavities contain free moisture. I nsects can attack the wood and eat through the softer sap­ wood, which is rich in proteins. The primary objective of so-called passive protection of the timber is to minimise the conditions under which such damaging organisms can thrive. Protection against fung i is therefore mainly aimed at limiting the moisture content of the timber. Such measures include, for example, providing overhanging eaves and protectin g plinths against splashing water. Furthermore, choosing a durable species of wood can elimi­ nate the need for chemical treatments (fi g . B 6. 1 1 ) . All the passive measures should certain­ ly be investigated before resorting to chemical preservatives. Chemical wood preservatives are based on the use of pesticides. The preservative must pene­ trate as deep as possible. We d istinguish between preservatives soluble in water and those containing solvents (see "Surfaces and coatings", p. 1 98 ) . I n recent years environmen­ tally compatible preservatives have appeared on the market alongside those that cause hygiene and ecology concerns. The new pre­ servatives include, for example, boron salts, which can penetrate deep into the timber cross-section when appl ied using pressure impregnation.

as fuel, the other half for paper production and building. Consequently, the forest is one of the largest and, at the same time, most inexpen­ sive producers of raw materials. From forest management to the Brundtland Report

Up until the 1 8th century carpenters them­ selves searched for suitable trees in the forest, felled them and worked them as required . Only as wood became scarcer did this tradition change to planned forest management. Since 1 7 1 3 wood has been used according to the sustainabil ity principle first devised by the Ger­ man forester Hans Car I von Carlowitz. At the start of the 1 8th century sustainabil ity meant that no more wood could be taken from the for­ est than could be regrown. This concept, initial­ ly i ntended for forestry management, was taken on board by the World Commission on Environ­ ment and Development (Brundtland Report) i n 1 987 a s a basis for a n integrative global policy strategy. Wood as a carbon storehouse

Biomass (wood ) is formed from the carbon d ioxide (C02) in the air, water ( HP) and trace elements from the soil with the help of chloro­ phyll and solar energy. During this process oxygen (02) is released. When it is burned, but also during natural de­ gradation by fungi and bacteria, the b iomass is broken down into carbon dioxide and water again as energy is released (fig . B 6.20) . Wood is made up of about 50% carbon (C) from the carbon d ioxide in the air. This carbon remains stored in the forests and timber prod­ ucts for the whole time between photosynthesis and the oxidation of the wood (degradation by fungi and bacteria, or combustion) . Wood therefore makes a major contribution to reduc­ ing carbon d ioxide concentrations. The forests of Europe hold about 20 times the amount of carbon dioxide that is released i nto the atmos­ phere every year through emissions. The use of wood and wood-based products in building prolongs this storage effect. And using more timber and so curtailing the production of steel and concrete reduces the emissions of carbon d ioxide even further.

Solar energy 1

0

-

-

/ 1 "

carbon dioxide + water 6CQ, + 6H,O

--.

oxygen + biomass 60, + C,HI2O,

a 56.5 MJ calorific energy

" r'\ V

1 .44 kg CO, 0.56 kg

1 kg wood kg 0,

1 8.5 MJ heating value

b

B 6.20

B 6.19

Physical parameters of board-type wood-based products B 6.20 Simplified illustration a Photosynthesis of wood b Combustion of wood B 6.21 -22 Structure made from cross-laminated timber, "Parasite" house, Rotterdam, Netherlands, 2001 , Korteknie & Stuhlmacher

Wood and sustainability

Forests cover approx. 30% of the Earth's land surface. Whereas forests in the developing countries have been d isappearing in recent years (-9%), stocks of trees in the industrial­ ised nations have increased (+ 3% ) . Based on this growth, it seems sensible to increase the use of timber products in Europe. Roughly half of the timber stocks available g l o­ bally (approx. 3.3 billion m3 annually) are used

B 6.22 75

Metal

B

The d iscovery and use of metals had a great influence on the cultural development of human­ kind in ancient times. Accordingly, these epochs have been named after the corresponding metals. Up until the New Stone Age, i .e . up until about 6000 BC, metals that occur in pure (native) form in nature were used to a limited extent, e . g . for jewel lery. The next milestone is around 4300 BC, which heralded the dawn of the Cop­ per or earliest Bronze Age in Central Europe. During this period techniques for extracting metals from ores, metal casting and the pro­ duction of tools spread . The discovery of the more hardwearing bronze - an alloy of copper and tin - in Egypt around 3500 BC characterised the next cultural epoc h . Bronze became popular for household utensils, weapons, tools, jewellery and much more besides. The ongoin g development of metal casting even made possi ble the first series pro­ duction runs. The outcome of these technical developments was new professions, and trade relations started to expand. New social struc­ tures formed in society, which led in turn to the first city-states. After about 1 200 BC iron began to replace bronze because it was more readily available. However, at first iron was d ifficult to work. The earl iest furnace for producing iron , the so­ called bloomery, was heated with charcoal and produced a lump of iron and slag from the orig­ inal iron ore. Considerable hammering was required to separate the slag from the iron and then turn the lump of iron into the desired shape.

Waterloo I nternational Rail Terminal, London, UK, 1 993, N icholas Grimshaw & Partners B 7.2 Overview of metals and their alloys B 7.3 Golden roof, Secession building, Vienna, Austria, 1 897, Joseph Maria Olbrich B 7.4 Iron frame, Gare du Nord, Paris, France, 1 863 B 7.5 Large-scale use of cast steel in industrialisation: cast iron wheels, steelworks in V6lklingen, Germany, 1 9th century. B 7.1

76

It was not until the 1 4th century that the tech­ n ique of using bellows in raised blast-furnaces to generate temperatures of about 1 500°C became widespread in order to reduce larger q uantities of molten iron. In his 1 2 books with the title De re metallica /ibri XII published in 1 556, Georg ius Agricola describes the state of the art of that time, techniques that did not undergo any noteworthy changes until the dawn of industrialisation in the 1 9th century. The consumption of great q uantities of wood had already led to the d isappearance of large areas of forest by the 1 4th century. The pro-

7.1

duction of 1 kg of iron required about 1 25 kg of wood to supply the necessary energy. But in 1 709 Abraham Darby succeeded in firing a blast-furnace with coke, and by the end of the 1 8th century coke was increasingly replacing wood as a fuel. This resulted in metal produc­ tion being transferred to coal-mining regions. It was in Coalbrookdale (UK) in one of these regions that the first cast iron bridge was built in 1 779. The growing demand for rolled iron products in the building industry encouraged further technical progess. Metal in architecture

Cramps of iron and bronze for holding together the individual stones of Greek and Roman structures were the first metal components used in the building industry. But it was not until the 1 9th century that metal i n the form of cast iron began to be used for load bearing ele­ ments. The methods of building initially fol­ lowed the practices that had been used for centuries for timber and stone. But delicate constructions quickly showed the unlimited shaping opportunities and the higher load­ carrying capacity of this material . One famous example is the reading room of the St Gene­ vieve l ibrary in Paris ( 1 850) by Henri Labrouste. The use of i ron left exposed was at first accept­ ed only for bridges, industrial structures and railway stations (fi g . B 7.4) . Owing to its effi­ ciency and fast erection, cast i ron was favoured for the world expositions in London ( 1 85 1 ) and Paris ( 1 889). Joseph Paxton used prefabricated cast iron components for his "Crystal Palace" in London in 1 85 1 , the size of which - 564 x 1 24 x 33 m - would even today cause some astonishment. In Paris on the other hand, renowned architects and artists protest­ ed against Gustave Eiffel's 300 m tower for the world exposition of 1 889. At the start of the 20th century, the easy mouldability of metals was used to great effect by the proponents of Art Nouveau (fig . B 7 . 3 ) . Development o f steel construction By the end of the 1 9th century it was possible to obtain large quantities of molten steel direct­ ly from pig iron using the Bessemer method invented in 1 856, which had enabled cheaper

Metal

Metals

Alloys

Alloying constituents

carbon content

carbon content

:;, 2 %

< 2 %

small amounts of: copper chromium

small amounts of: nickel chromium vanadium tungsten

small amounts of: titanium copper etc

copper 80-90% tin 1 0-20%

copper 65% zinc 35%

B 7.2

production of steel on a large scale. It thus became possible to construct large industrial plants (fi g . B 7.5). One of the first steel bridges in Europe was that over the Firth of Forth in Scotland ( 1 889). The efficiency of steel and the economic devel­ opments in America led to a new type of build­ ing - the skyscraper, which underwent a rapid evolution: the first high-rise blocks in Chicago and New York were built around 1 890 and had 1 0-1 5 storeys (fig . B 7 .9) , but the Empire State Building built just 40 years later had 1 03 stories and even today is still in the top 1 0 of the world's tallest buildings. For the first time in history of architecture, the external envelope could be completely transparent (fig . B 7 . 1 ) - thanks to structural steelwork.

This particular metallic bond allows us to explain all the physical properties such as high density and strength, the high melting point plus the good thermal and electrical conductiv­ ity. Metals can be moulded and usually have shiny surfaces. Some metals exhibit magnetic properties. Their high thermal conductivity means that they feel cold to the touch, but inci­ dent solar radiation is absorbed and results in a significant rise in temperature. One particular feature of the metals is their plastic deformation (the so-called yielding) under high loading. For their use in building therefore it is not the u ltimate load that governs but rather a stress equivalent to the yield point, which is reached at an elongation of 0.2%. B 7.3

Deposits and production

Contemporary applications The majority of metal used in the modern con­ struction industry is in the form of rolled steel sections for loadbearing members in single­ storey sheds and high-rise buildings, and steel bars for reinforced concrete structures. How­ ever, metal is also used in many components from outside facilities to roof elements (e.g. cladding and roof coverings) , and for fixings, fasteners and services. Remarkable examples of the use of metal facades can be seen at the offices of the John Deere Company dating from the 1 960s (Eero Saarinen) , which uses weathering steel, the Lloyds headquarters in London (Richard Rogers) , which is clad with stainless steel panels (fig. B 7 . 1 1 ) , and the copper facade to the railway signal box in Basel by Herzog & de Meuron (fig. B 7. 1 6) . Further possibilities for steel construction can be seen in the designs of Frei Olto (see "Synthetic materials", p . 90, fig. B 9. 1 ) , which reveal the path of the forces. Norman Foster showed us the boundaries of technical feasibility in steel high-rise building i n his design for the 1 000 m Mi llennium Tower in Tokyo.

Although the majority of chemical elements are in fact metals, they account for less than 1 5% of the material in the Earth's crust. Only the so­ called precious metals such as gol d , si lver and p latinum occur in nature in their pure (native) form. The metals important for the building industry (e. g . iron, aluminium, copper) are obtained from ores (sulphides and carbonates) but first have to be converted to oxides in vari­ ous preparatory processes before they can be smelted (reduced) in blast-furnaces. Classification of metals

We distinguish between heavy metals (> 4500 kg! m3) and light metals « 4500 kg/m3) . The classi­ fication into ferrous and non-ferrous metals (fi g . B 7.2) shows the great importance of iron and its alloys in comparison with the other met­ als. Metals can be pure - consisting of the atoms of one chemical element - but can also be combinations of two or more elements (so­ called all oys) , i.e. a blend of a metal and anoth­ er substance (metallic or non-metallic such as silicon or phosphor) . Even small proportions of other substances can change the material properties of metal al loys. This allows the mate­ rial to be adapted for diverse applications.

Metal

Material lifecycle

Metals (Greek: metal/on mine) are those chemical elements whose atoms combine to form crystalline structures with free electrons. =

Metals can be returned to the production proc­ ess without impairing the q uality of subsequent products. In fact, recycling represents an B 7.5

77

Metal

Shaping and jointing of metals

B B

B B

7.6 7.7

7.8 7.9

Shaping and jointing of metals Semi-finished products made from metal sheets: a Trapezoidal profile sheet metal b Perforated sheet metal c Stamped sheet metal d Expanded metal Ropes and rods: e Cable net f Knitted fabric g Woven meshes of strips h Woven meshes of ropes and rods Sections: i Rolled stainless steel sections j Extruded aluminium sections (window frames) Castings: k Cast steel node I Washbasin tap Semi-finished products made from various metals Structural steelwork, Times Tower, New York, USA, 1 905, Daniel Burham

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advantage because it requires much less ener­ gy to melt down the metal. The reuse q uota for scrap metals sent for recycl i n g is 90%, in the case of steel almost 1 00%. Behaviour in fire, fire protection

Metals are incombustible, but lose their strength at high temperatures. The modulus of elasticity and the yield point fal l , and the metal deforms. The maximum temperature for steel is approx. 500-600°C, depending on the cross­ section. In order to protect building occupants against the failure of components in a fire, structural steelwork must be protected, either by enclosing it in a fire-resistant material or coating, by filling hol low members, or by install­ ing fire extinguishing systems. Corrosion

Corrosion is the chemical or electrochemical reaction of a substance. Metals oxid ise in high humidities and through contact with wet or damp materials. Galvanic corrosion takes place at the point where two disparate metals are in contact in the presence of an electrolyte, e . g . water. I n this case the less noble metal is corroded, a

fact that must be taken into account by consid­ ering the electrochemical series when using non-ferrous metals. The series extends from the non-noble metals magnesium and aluminium to the noble metals silver and gold. Simplified , the series looks l i ke this: Mg-AI-Zn-Cr-Fe-Ni-Sn-Pb­ Cu-Ag-Au. In order to prevent corrosion, p i pes of copper, for example, should be laid down­ stream of those made from iron or zinc, and not vice versa. As the working or machining of metals can change their properties, especially in the case of steel , an electrochemical reaction can take place even within a steel component, e . g . at bending points, welds or through alloying con­ stituents.

7.6

Passive corrosion protection is provided by numerous forms of metallic and non-metallic coverings such as paint, powder and plastic coatings, enamel, galvanising and zinc plating. Such coatings and coverings should not be damaged during erection (e.g. through bolted connections) . Corrosion protection prolongs the l ifetime of external components or internal components where the humidity is high. Natural protective layers Copper, aluminium, lead and zinc plus a number of steel alloys (stainless steel , weather­ ing steel) form protective layers on their surfac­ es that prevent further corrosion. Shaping and processing of metal

Corrosion protection We distinguish between two fundamental approa­ ches to the protection of components against corrosion: active and passive protection. Active protective measures are forms of con­ struction that present I ittle or no chance for cor­ rosion to gain a foothold. The targeted "sacrific­ ing" of a less noble metal with an electrically conductive attachment to the component can actively prevent corrosion.

We d istinguish between cold- and hot-working and mechanical machining processes. In cold­ working the geometry of the atomic metal microstructure is altered mechanically. In hot­ working it is not the absolute temperatures (for steel 900-1 300°C, for lead 20°C) that govern, but rather the possible rearrangement of the crystal lattice, a process that also occurs dur­ ing the hardening and tempering of steel. Therefore, rol l i n g , pressing and forging can be

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used for both hot- and cold-workin g depending on the material (fi g . B 7 . 6 ) . Forging Forging can be carried out manually or by machine using a hammer and anvil or with pressing moulds (forg i n g d ies) . Forg ing can be both a cold- and a hot-working process. Diverse shapes are possible. Casting Casting permits any shape to be formed . How­ ever, further processing of steel castings is only possible using machining methods. Tin and bronze are suitable for the production of delicate, precision castings. Rolling Workpieces (e.g. rolled steel sections) are shaped in several operations in a rolling mill by applying high contact pressures through a system of variously sized rolls. Extrusion In extrusion the metal is forced through an opening (die) to form the desired final shape. This process i s particularly suitable for non­ ferrous metals, which enables, for example, complicated aluminium cross-sections for win­ dow frames to be produced. Extrusion can be both a cold- and a hot-working process. Drawing Wires, rods and reinforcing bars are produced by drawing, usually a COld-working process. Twisting Sections, rods and wires for cables are twisted about themselves. The enlarged surface area of twisted reinforcing bars, for instance, improves the bond between steel and concrete.

Mechanical machining A wide range of metal products i n the building industry require mechanical machi n i n g . Milling, dri l l i n g , fi l i n g , sawing and turni n g are the so­ called material-removal machining options. It i s possi ble t o c u t a thread in sol id material, mill holes, or turn hinges for doors and windows, to name just a few examples. Bending and stamping are among the COld-working process­ es (e.g. for sheet metals) . And the folding of thin sheet metal creates rainproof joints for roof surfaces (see "The building envelope", p. 1 24 ) . Jointing techniques

N umerous methods are used to join metals together. We d istinguish between detachable joints such as screws, bolts, nails, rivets and pins, and the non-detachable ones such as welding, solderi n g , brazing and bonding with adhesives. Welding involves melting the workpieces at their point of contact to create a material bond at the joint. In soldering, a molten metal or an al loy with a low melting point joins together two other metal workpieces. Products, semi-finished products

The great number of metal products relevant to building means that it is only possible to men­ tion a few groups here: castings, drawn wires, rods, reinforcing bars and meshes, p i pes, steel sections, welded sections, cold-formed sec­ tions, extruded sections, rings, collars, d iscs, bolts, screws, turned parts and many forms of sheet metal (figs B 7 . 7 and B 7 . 8 ) .

Ferrous metals

I ron and its alloys, especially steel, are suitable for diverse technical applications and are therefore required in such large q uantities that today the production plants shape many Euro­ pean cities.

Iron

I ron is the most widely used metal worldwide. I ron deposits account for about 5% of the chemical e lements available in nature and it thus ranks fourth after oxygen, silicon and alu­ minium. Pig iron contains approx. 4% carbon and is brittle. Chemically pure iron is hardly ever used because of its low strength and rapid oxidation (corrosion) . But as the proper­ ties of iron can be i mproved by reducing the carbon content, it is mainly further processed to form steel and other iron al loys. Production and recycling I ron ore is mixed with lime i n a blast-furnace and reduced to iron at temperatures of 1 500°C. The process also produces slag and gases from the non-metallic constituents in the iron ore. Some of the carbon in the iron dissolves, which lowers the melti ng point. The result is pig iron containing carbon, which is heavier than the slag and so s inks to the bottom of the fur­ nace from where it can be drawn off continu­ ously. The addition of scrap metal to this proc­ ess results in two advantages: firstly, it improves the qual ity of the pig iron, and sec­ ondly, the primary energy requirement of recy­ cling is only about 20-40% of that req uired for new production. Materials for casting Compounds of iron with a carbon content > 2% are known as cast iron, those with < 2% cast steel (fig . B 7 . 1 0) . The properties and designa­ tions of cast iron depend on the form of the car­ bon in the solidified casting material. We d istin­ guish between cast iron with lamellar graphite (grey cast iron, GJL), with spheroidal graphite (ducti le cast iron, GJS) and malleable cast iron (GJ M ) . The latter turns a l i g hter colour in an oxi­ dising atmosphere (white cast iron). In sand moulding the carbon remains in the material and gives it a dark colour (grey cast iron, L) . There are also al loys of cast iron . Cast i ron

79

Metal

Density

Abbreviation

Ferrous metals

[kg/ m']

Thermal conductivity

Tensile Coefficient Electrical of thermal conductivity strength expansion

Modulus of

Elongation Yield

elasticity

at failure

& 0.2% proof stress

[W/ mK]

[mm/mK]

[m / flmm']

[N / m m']

[%]

[N / mm']

0.8-0.3

98/285 2

[N / mm']

Cast iron cast iron (lamellar graphite)

GJL

7 1 00-7300

40-50

0.Q1 2

5-7

1 00-450 (600-1 080)'

78000-143 000

cast iron (spheroidal graphite)

GJS

7 1 00-7200

36.2-31 . 1

0.Q1 3

5-7

400-900 (700-1 1 50) 1

1 69 000- 1 76 000

7850

40-50

0.Q1 2

5-7

380-1 1 00

7850

56.9

0.Q1 2

5

7850

48

0.01 2

1 8-2

240-600

2 1 0 000

7-25

200-830

340-470

2 1 2 000

25

235

5

450-680

2 1 2 000

1 7-20

275-355

Steel cast steel structural steel Fe 360 BFN (RSt 37-2)

WT St 37-3

Fe 5 1 0 C (St 52-3

WT St 52-3

U)

S235JR

1 .0038

S235J2W

1 .8965

S355JO

1 .0553

S355J2W

1 .8965

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1 .4301

7920

1 4. 5

0.01 6

1 .5

500-700

200000

45

1 90

V4A (X 6 CrNiMoTi 1 7- 1 2-2)

1 .4571

7960

15

0.01 7

1 .4

500-730

200000

45-50

2 1 0-255

1

In contrast to steel, the compressive strength and tensile strength of cast iron are not identical. The compressive strengths are therefore given in brackets.

2 Owing to the low elongation at failure, these values apply to a 0 . 1 % proof

materials are brittle, cannot be shaped by forg­ ing, and only certain types can be machined . The melting point of cast iron is lower than that of steel . Cast iron with spheroidal graphite can be welded to a limited extent and i s more resis­ tant to corrosion. A cast steel that undergoes no further shaping is known simply as cast steel (GS) . Cast steel al loys can be readily welded to structural steel and are used for jOints with complicated geometry (fig . B 7 . 7 ) . Applications Cast i ron in building is suitable for drain p i pes, radiators and bath tubs, for instance. Inspec­ tion covers and hydrants made from malleable cast iron are also common. Fittings, hardware and keys (i.e. ironmongery) are mad e from white cast iron. Components made from d uctile cast iron are used for connecting tie bars, guy rods, bracing , etc. If no test certificates are available, the proper­ ties of load bearing cast parts must be proven in elaborate tests. This is the reason for the building industry's sluggish acceptance of the more efficient casting materials made from the special alloys that have been developed i n recent years.

B 7.10

Steel

Steel is an alloy of iron with a carbon content < 2 % . Stee l with a low carbon content has a higher melting point, but can be forged more easily and is less brittle. The modulus of elas­ ticity and weldabil ity are the decisive factors contributing to the wide use of steel in build i n g . Structural steel contains approx. 0.2% carbon. Proportions of other chemical elements - even very tiny amounts - can influence the properties of the steel quite considerably, e . g . corrosion behaviour. New steel variations are constantly being added to the 2000+ types currently covered by standards. Production and recycling There are three methods for reducing the car­ bon in pig iron and thus producing steel. In the air refining process the carbon is removed from the pig iron, either by injecting air (Thomas process) or pure oxygen (Linz-Donauwitzer LD method ) . T h e open-hearth refi ning processes include the Siemens-Martin and the electric-arc furnace processes. The Siemens-Martin process was developed by Wilhelm and Friedrich Siemens

in 1 856 for convertin g scrap metal back into steel. Using a system for preheating gas and air, the temperature of approx. 1 800°C neces­ sary for producing molten steel is generated in a d ish-like furnace. I n 1 864 Pierre und Emile Martin managed to apply this method success­ fully, and it was set to remain the most impor­ tant method for producing steel for the next 1 00 years. The electric-arc furnace method requires an electric arc to be fired between two electrodes. The extremely high temperatures generated by the arc are sufficient to melt even hig h-quality metal alloys. The LD and e lectric-arc furnace methods are the most common steel making methods in use today. Heat treatment The physical properties of steel can be changed through specific heating and cooling or hammering (forging) because - depending on the carbon content - various crystal struc­ tures ensue at temperatures of 700-1 500°C. We d istinguish between annealing, hardening and tempering. Steel alloys

Steel alloys with other constituents must be clearly d istinguished from steel because they can exhi bit considerable d ifferences in terms of their properties. The development of efficient steel alloys is an ongoing process, and high­ strength alloys of this kind are used , for exam­ ple, in automotive and mechanical engineering applications. Stainless steel Corrosion-resistant steels are usually grouped together under the heading of stainless steel . Such al loys contain a t least 1 0% chromium, but also other metals such as nickel, molybdenum, titanium, vanadium and tungsten; the carbon content l ies below 1 .2%. In contrast to steel , stainless steels form a protective, so-called passive, coating under normal conditions, which renews itself if damaged. Nevertheless, seawater or high humidity in combination with salts (e.g. in thermal baths) can still attack some types of stainless steel. B 7.1 1

80

B 7.12

Metal

B 7 . 1 0 Physical parameters of ferrous metals common in building B 7.1 1 Stainless steel facade, Lloyds headquarters, London, UK, 1 986, Richard Rogers Partnership B 7. 1 2 Weathering steel , Kalkriese Museum, Bramsche, Germany, 2002, Gigon + Guyer

B 7 . 1 3 Various anodised aluminium surfaces, Town Hall, Scharnhausen, Germany, 2002, Jurgen Meyer H . B 7.13

The energy required to manufacture stainless steel is higher than that for steel owing to the additional alloying elements requ ired . As stain­ less steels often require no further surface fin­ ishes, they can be readily recycled because the electric-arc furnace process can melt down these high-quality steels. Various mechanical surface treatments can be used on stainless steel, e . g . brushing, grinding, acid-etching or sand-blastin g . Building authority approval is required when stainless steel is to be used for load bearing applications. Stainless steel is used for facades, roof coverings, pipes (flues), safety barriers, handrails, kitchen furniture, hardware, fasteners and much more. Weathering steel Alloys of steel with additions of copper, chromi­ um, nickel and phosphorus gradually form a permanent layer of rust upon exposure to the atmosphere (fig . B 7 . 1 2) . Owing to this process of rust formation, minimum thicknesses should be taken into account in the case of load bear­ ing components. Nevertheless, in marine envi­ ronments or other unfavourable climatic condi­ tions the rust layer does not provide permanent protection.

Non-ferrous metals

Compared with aluminium, lead, zinc, copper and their alloys, silver, gold, magnesium and titanium are less important in the building industry and therefore are not considered any further here. Aluminium

Although aluminium is the third most common element and the commonest metal in the Earth's crust, it was not discovered until the 1 9th century. Its extraction was so complicated that it was initially treated as a very precious metal. Production and recycling The raw material of aluminium is bauxite, which is obtained from open-cast mines . In a process not unlike that used for iron, aluminium oxide is

obtained first. Caustic soda (sodium hydroxide layer a n d i s therefore very durable. On building solution) is used to separate the aluminium sites aluminium must be protected by sheeting or similar means against the effects of concrete hydroxide from the other constituents of the ore and lime or cement mortars because their alkali and this is subsequently heated to 1 200°C to constituents can attack the surface of alumini­ obtain aluminium oxide. The high meltin g tem­ um. perature of approx. 2000°C is lowered by add­ The oxide layer on aluminium can be reinforced ing cryolite (Na AI F6) . Aluminium can then be 3 extracted from the mixture at approx. 1 000°C by considerably through anodisin g . Depending on the period of immersion in an electrolytic bath, applying an electric current of between 30000 colours between light grey, grey-brown, bronze and 1 00 000 A. The process requires a high and dark brown are possible (fig. B 7 . 1 3) . energy input and the by-products of the elec­ Joints and junctions o n aluminium construc­ trolysi s represent a problem for the environ­ tions and facade cladding must take into ment. This i s why aluminium is already being recycled to a large extent, which saves 75-90% account the fact that the coefficient of thermal of the primary energy, the exact saving depend­ expansion of aluminium is about twice that of steel . ing on the method of generating the electricity. Nevertheless, in the price of aluminium the cost Applications of energy accounts for about 40%. Extruded sections for supportin g frameworks, Properties and processing windows and post-and-rail facades represent the most i mportant applications for aluminium Aluminium is used wherever its low weight in building . With correspondi ngly large num­ only about a third of that of iron and steel - is beneficial. bers, the forms of the extruded sections can be Aluminium materials can be mil led, sawn and varied almost at will with l ittle effort. Further applications include plain and profiled sheets drilled . They are light in weight, read ily mould­ for facades and roofs, perforated sheets ed, easy to work and can be polished. Shaping is performed by rolling, stretch-form­ (acoustic ceilings), lamp bodies, hardware made from cast aluminium and much more i n g , pressing, drawi n g , forging and upsettin g . Aluminium is more ductile than steel a n d so besides. Moreover, aluminium foil is popular for waterproofing. extruded sections can be manufactured with considerably less energy input. Aluminium foams Aluminium can be welded only in an oxygen­ free atmosphere because the formation of the Metal foams made from aluminium exhibit a lower thermal conductivity and relatively good layer of oxide must be prevented during the wel d i n g procedure as wel l . sound insulation properties. They have a good compressive strength coupled with a low The aluminium alloys used i n building are gen­ erally also referred to simply as aluminium. weight and are easy to work. They are already in use in the automotive sector. In principle, it is These alloys contain about 2-2.5% of elements possi ble to produce such foams from other such as s i l i con, magnesium, copper, manga­ metals as well . nese, etc. The European material numbering system includes a material designation for every type of Lead After aluminium, lead is one of the commonest metal. For example, aluminium alloy EN AW 3 1 01 has the chemical designation AIMn 1 . The metals in the Earth's crust. It is a non-ferrous main constituent of this material, besides alu­ metal which is classed as a heavy metal because of its high density. minium, is manganese (0.9-1 .5%) plus about 2% of other alloying constituents (Fe, Si, M g , Zn, Properties Lead has a low tensile strength and exhibits Cr, Zr and Ti) . Aluminium corrodes immediately upon exposure large temperature-induced changes in length. to the air, but forms a permanent protective It can absorb sound waves, x-rays and radio-

81

Metal

active radiation. Lead is attacked by strong acids, fresh mortar and concrete, but is extremely resistant to corrosion. Upon expo­ sure to the air it forms a permanent l ayer of oxide that subsequently carbonates with car­ bon dioxide. This layer is l ight grey in colour and insoluble in water. As lead is very soft, it is easy to rol l , and easy to shape by hammering and moulding . It can also be soldered and welded. Lead has a matt grey colour. Production and recycling A lead sulphide concentrate is obtained after several passes throug h so-called flotation cells. This involves frothing up the finely ground ore and copious aeration in order to separate the metal compounds from other constituents. The subsequent smelting of the dried concentrate permits the addition of a high proportion of sec­ ondary raw materials such as lead scrap. The process requires a great deal of energy and a toxic dust is produced, which must be d is­ posed of in landfil l sites. The recycling quota is in excess of 50%, which can help to save about 40% of the energy required for production. Applications Sheet lead is suitable for roof coverings and facades (fi g . B 7 . 1 4) . Owing to its corrosion resistance lead is also used as a protective sheathing (e.g . for electric cables) . Lead is suitable for shielding radiation in nucle­ ar medicine applications and as a raw material for rustproofing paints (red lead ) . Owing to its toxic effects lead should be avoided these days because it can become enriched in the food chain. Zinc and titanium-zinc

The Romans were already using zinc in the form of brass, without being aware of the zinc content itself. Marco Polo described the pro-

B 7.14 82

duction of zinc oxide for medicinal purposes at the end of the 1 3th century. I n d ustrial production of zinc began around 1 850. Zinc alloys ( e . g . titanium-zinc made from 99.995% zinc plus 0.003% titanium) have high­ er strengths than the relatively brittle zinc itself. The alloys can be soldered and welded and have a lower thermal expansion than zinc. It is for this reason that the building industry makes use of titanium-zinc almost exclusively. Zinc i s weather-resistant because, like lead, it forms a permanent layer of carbonate when exposed to the air. It is therefore frequently used as a protective coatin g (galvanising) on other metals such as steel, copper, etc. Production and recycling Zinc ores (sphalerite, smithsonite and zinc oxide) are prepared using froth flotation - simi­ lar to lead. To extract the zinc, both the so­ called dry process, in which coal reduces the zinc oxide in the by-product coke oven, and also the wet process, in which the reduction is performed electrolytically, are employed. The preparation of the zinc ore directly at the mine is an attempt to save energy. About 30% of the worl dwide production of zinc is obtained from secondary material (scrap). Applications Titanium-zinc in sheet form is suitable for facades (fig . B 7 . 1 5) , roof g utters and pipes. Zinc can be cast very precisely and in very intricate moulds. There are many z inc-based alloys relevant to the building industry, e . g . d ie­ cast zinc for hardware, brass, nickel silver and solders for solderin g . O n e i mportant area o f application for zinc is its use as corrosion protection on steel compo­ nents because zinc is much more resistant owing to the permanent protective layer that

B 7.15

forms. There are many methods for applying this protection to steel components for use externally: hot-di p galvanisi n g , electrogalvanis­ i n g , zinc spraying, etc. The durabil ity of zinc coatings essentially depends on the carbon dioxide content of the surrounding air. Copper

The word copper stems from the Latin word cuprum and is evidence that the Romans mined the ore on the island of Cyprus (Latin : cyprium) . Copper is one of the heavy metals. Properties Copper has a shiny red colour and is very hardweari n g . It is easy to work, is easy easily shaped, soldered and welded, but is difficult to cast. Copper conducts heat and electric cur­ rent very wel l . Pure, soft copper is d ifficult to work, but its strength improves considerably in the form of copper al loys. Patina Copper is resistant to effects of gypsum, lime and cement, and forms a dense, greenish layer of copper salts upon contact with the air. Under normal urban conditions this patina builds up over a period of about eight years. Its colour d uring this process ranges from red-brown to dark brown and grey to the typical green. This process can be reproduced chemically prior to erection (so-cal led pre-patination) . Verd igris on the other hand is a copper salt that forms in the presence of acetic acid and is often m istaken for the copper patina. In con­ trast to the patina, verdigris is toxic and soluble in water. Production and recycling Like lead and zinc, the copper ores chalcopy­ rite and chalcocite are prepared using the froth flotation process. The reduction takes place in

B 7.16

Metal

Non-ferrous metals

Aluminium

EN AW-7022

(AIZn5Mg3Cu)

Lead

[kg/m"]

Electrical Thermal Coefficient of conductivity thermal expansion conductivity [ml!1mm"] [mm/mK] (W/mK]

Density

Tensile strength [N/mm"]

Modulus of elasticity [N/mm"]

Elongation at failure [%]

Yield & 0.2% proof stress [N/mm"]

2703 ' /2699 '

222

0.023

8-25 ' /2-8 '

1 30

n.a.

37 20

72 200

2780

4 1 0-490

70 000

3-8

330-420

1 1 340

35

0.029

4.8

1 0-20

20000

50-70

5-8

90-1 20 ' / 1 50-230 '

40-70 '/ 80-1 1 0 '

Zinc

7 1 30

113

0.033/0.023'

1 6.9

1 50/220 '

94000

25/ 1 5 '

1 60/220

Titanium-zinc Z1 (ZnCuTiAI)

7200

1 09

0.022

17

1 50-220

80000

;,, 35

1 00-1 60

Copper

8940

394

0.D1 7

1 20 000

25-1 5 ' / 50-30 3

8900

329

0.01 7

57 n.a.

1 60-200 ' / 200-250 3

CW024A; 2.0090

200-51 5

1 32 000

Copper-tin alloy (bronze)

8600-8800

54-75

0.01 7-0.0 1 9

ca. 9

240-300

Copper-zinc alloy (brass)

8300-8500

1 1 7- 1 59

0.01 7-0.020

ca. 1 6

370-740

CuZn37; CW508L; 2.321

8400

121

0.020

ca. 1 6

740

' cast

' rolled

3 annealed

40-60 1 / 1 00-1 50 3

3 - 40

35-320

80000-1 06000

5-12

1 30-1 80

75 000-1 20000

1 0-20

1 50 - 490

10

440

1 1 0 000

' Values for parallel with and transverse to rolling d i rection B 7.17

a converter. However, for applications in elec­ trical engineering, which account for about 60% of copper production, the copper is extracted electrolytically (electrolytic copper) . More than 50% of the production is based on recycled material, which saves 86% of the pri­ mary energy requirement. Processing and applications All the conventional metalworking techniques are suitable for copper and its alloys. But the material's high thermal conductivity makes it difficult to weld, although it is easy to solder and bond with adhesives. Sheet copper is used for facades and roofs (fig. B 7 . 1 6) but is also suitable for waterproof­ ing tasks because it can be bonded with bitu­ men. Copper is suitable for manufacturing pipes, e.g. for heating systems, and is widely used in electrical engi neerin g (see "Building services", p. 1 50). Alloys of copper and tin: bronze

The name bronze stems from the Latin brundi­ sium (from Brind isi) should these days really be replaced by the standardised designation "alloy

of copper and tin" because there are also alloys of copper and aluminium (previously known as aluminium bronze) . Bronze is produced in a smelting furnace at 1 000°C and contains a pro­ portion of tin amounting to between 1 0 and 20%. Bronze is extremely durable and weather­ resistant. It is harder than brass and copper, and exhibits good resistance to corrosion and abrasion, which is why it is used for long-lasting bearing bushes. Bronze has a dark surface which can be pol­ ished to a shiny gold colour with little effort. Evi­ dence of this can be seen on the many bronze sculptures and objects in public areas - parts that frequently touched by admirers and pas­ sers-by have shiny, pol ished surfaces. Bronze is suitable for pipe couplings, hardware and gas, water and steam fittings. In addition, bronze i s used for casting bells and artistic objects. Owing to its durabi l ity, bronze window frames and doors can be found on many his­ torical buildings, even on prestigious contem­ porary buildings (fi g . B 7 . 1 8) .

Alloys o f copper and zinc: brass etc.

These alloys contain at least 50% copper. These days we disti ng u i sh wrought copper alloy (previously known as brass) from gunmet­ al and nickel silver. The wrought copper alloy consists of 55-85% copper plus zinc. Gunmet­ al is an alloy of copper, zinc and tin (each 1 -1 0% ) . N ickel silver consists of 50-60% cop­ per, 1 0 -25% nickel and zinc. Copper alloys are read ily shaped, easy to work and - in contrast to pure copper - can be cast too. Brass is h i ghly resistant to corrosion and has a shiny gold appearance after working or polish­ ing. However, over time the surface tarnishes to a dark matt finish. Copper al loys are used in many applications, e . g . brass for electric terminals, screws and nuts, pipe fittings and hardware. One architectural example of the use of a woven metal mesh made from brass is the syn­ agogue in Dresden (fi g . B 7 . 1 9) . Nickel silver i s suitable for contact surfaces i n electrical engineering, but also for hardware and pipe fittings.

B 7.14 Cladding of sheet lead, Parco dell a Musica Auditorium, Rome, Italy, 2002, Renzo Piano B 7.15 Cladding of sheet titanium-zinc, Guggenheim Museum, Bilbao, Spain, 1 997, Frank Gehry B 7.16 Cladding of copper strips, signal box, Basel, Switzerland, 1 999, Jacques Herzog & Pierre de Meuron B 7.1 7 Physical parameters of non-ferrous metals and alloys used in the construction industry B 7.18 Bronze facade sections, Seagram Building, New York, 1 958, Ludwig Mies van der Rohe B 7.19 Brass mesh fabric, Dresden Synagogue, Germany, 2001 , Wandel Hoefer Lorch + Hirsch

83

Glass

B 8. 1

The invention of the sand core technique ena­ bled g lass to be made in small q uantities after about 6000 BC. The blowing iron developed by Syrian craftsmen around 200 BC meant that it was possible to produce transparent vessels. Roman builders were already using a form of cast glass for windows. However, owing to the method of production, the glass was not trans­ parent, merely translucent. G lass production between the 4th and 1 9th centuries was dominated by two methods. I n the crown g lass method the glass blower creat­ ed a circular pane up to 2 m in d iameter by rotating the glass around the blowing iron. This method of production left the typical raised centre section - the bullion. Larger areas of glazing were created by joining together such panes and smaller g lass fragments by means of lead cames. Contrasting with this, the blown cylinder sheet g lass process enabled the production of larger, almost flat panes. To do this, the blowing iron was used to form a cylinder that was then slit while still hot and subsequently rolled out on a flat bed. However, the surface finish possible with this method was far less uniform than that of a pane of crown g lass. The next major development took place in France in 1 687: Bernard Perrot developed the method of casting g lass on a preheated cop­ per plate and subsequently i mproving the sur­ face finish by grinding and polish i n g . Mirrors were produced by polishing one side only. Products made with this method were known as pol ished plate glass. The demand for timber for glass production was enormous during this period because it was needed to provide heat and to provide potash. G lass therefore remained a luxury reserved for prestigious buildings until well into the 1 8th century. The windows of Gothic churches are excellent examples of the skills of the glass blowers of this period. B 8.1

Glass pavilion at the Summer Academy in Rheinbach, Germany, 2000, Marquardt Architekten

Industrialisation

B 8.2

Systematic classification of glass products

B 8.3

Physical parameters of silicon-based glass

B 8.4

Glass curtain wall, Bauhaus, Dessau, Germany,

B 8.5

Profiled glass facade, extension to the art gallery

During the 1 9th century glass manufacturers began to fire their melting furnaces with coal. New methods optimised the process of melting and reduced the consumption of solid fuel . Lucas a n d Robert Chance improved the blown

1 926, Waiter Gropius in Winterthur, Switzerland, 1 995, Gigon + Guyer

84

cylinder sheet g lass process in 1 832 by unroll­ ing and stretching the slit cylinder in a furnace. Thanks to this new technique it became possi­ ble to produce the large numbers of better­ qual ity panes, e . g . for the Crystal Palace in London ( 1 85 1 ) . The production of glass became more efficient and cost-effective thanks to these various technological developments. In 1 905 - more or less at the same time - Emile Fourcault and Emile Gobbe from Belgium as well as the American I rving Col burn developed different methods of drawin g flat glass directly out of the melt. By 1 9 1 9 Max Bicheroux from France had man­ aged to combine the various operations for producing cast g lass by shaping the hot glass with cooled rollers, cutting it while stil l hot and then conveying it on flat beds through an annealing lehr. It was not until 1 959 that manufacturers were in a position to produce really flat g lass. I n that year Alastair Pilkington invented the float glass technique in which the glass is poured onto a bath of liquid tin and allowed to solidify. Owing to the efficiency of this method, it quickly became established for producing almost all types of flat g lass. Today, a typical float glass plant can produce about 3000 m2 of hig h-quali­ ty glass every hour. Glass in architecture

The palm houses, railway stations and market halls of the 1 9th century were already able to incorporate fully g lazed facades. The architects of the time were fascinated by the chance to provide their bui ldings with totally transparent external walls. As early as 1 9 1 9, Ludwig M ies van der Rohe put forward a radical design for a total ly glazed high-rise building in Berlin (which was never b u i lt) . The Bauhaus building in Des­ sau (Waiter Gropius, 1 926, fig. B 8.4) is regard­ ed as an early example of a large glass facade. One of the first residential buildings to make use of translucent hollow glass blocks was Pierre Charreau's "Maison de Verre" in Paris ( 1 932 ) . The first ful ly g lazed residential blocks in Ameri­ ca appeared in the early 1 950s (Ph i l i p Johnson and Ludwig M ies van der Rohe) , also glass curtain walls for office buildings, which are still a beloved medium of many architects today.

Glass

Glass products

Pressed glass

Glass fibres

glass brickslblocks glass tiles glass roof tiles

glass for greenhouses profiled glass

Metal composite wired polished plate glass

fusing patterned glass

wired patterned glass

sand-blasting

wired profiled glass

optical fibres

foam glass­

glass fleece

insulating materials

glass cloth

composite laminated safety glass

sheet glass optical glass bent glass

glass-fibre insulating materials

treatment

wired glass

Drawn glass

Foam glass

polished plate glass Surface

Thermal

treatment

treatment

sand-blasting

self-cleaning

toughened safety glass

acid-etching

anti-reflection

heat-treated glass

silk-screen printing

angle-selective

si lk-screen printing

insulating glass

radiation-selective

acid-etching

sound-insulating glass

adaptive

fire-resistant glass

phototropic/thermotropic B 8.2

The oil crisis of the early 1 970s gave impetus to the advance of glass technology; the develop­ ment of double g lazing systems and coatings encouraged the wider use of g lass. One excel­ lent example for a thermal break of great trans­ parency is the pyramid at the Louvre in Paris (fig. 8 8. 1 3) .

Glass as a building material

Glass in the general sense is an amorphous solid made from inorganic raw materials. This amorphous state ensues when a melt cools too rapidly for a crystalline structure to form. We could therefore call glass a sol idified liquid, although this would not be scientifically correct. Isotropy, solidity and thermal behaviour are three special qualities of glass that depend on this state. The constituents of glass for building are defined in EN 572 as silicon dioxide (Si02), cal­ cium oxide (CaO), sodium oxide (Nap ) , mag­ nesium oxide (MgO) and aluminium oxide (AIP3) ' The "normal" g lass accounting for the majority of applications in building consists of 75% silicon dioxide, 1 3% sodium oxide and 1 2% calcium oxide.

Properties

Like all materials, glass absorbs radiation. How­ ever, it does this in a range that is invisible to the human eye and therefore glass appears to be transparent. Glass is hard , resistant to wear and has a h i g h compressive strength (fig . 8 8.3) . An exact tensile strength, however, cannot be determined owing to the great brittleness of this material and the relatively high surface stresses. A decisive factor for the strength is hence the qual ity of the g lass surface. Even immed iately after production, microscopic flaws can appear on the surface whose significance or otherwise cannot be meani ngfully assessed without extensive examination. Furthermore, g lass exhibits the property of non-critical crack propagation. This means that cracks on the sur­ face of the g lass can also propagate even if the glass is not subject to any significant load. The breaking of a pane of glass may therefore not have anything d i rectly to do with the tri g gerin g event. I nterestingly, the high surface stresses in glass enable it to do just the opposite, i . e . to close up damage on the surface, e . g . cracks, to a certain extent. This process depends on the surrounding medium; in water for example, this capabil ity is lost. All these properties mean that the probabi lity of fai l u re must be taken into account when design­ i n g glass for structural purposes. And although g lass is incombustible, its brittleness means that it can accommodate only minor thermal

stresses. Only special fire-resistant glass can withstand temperature d ifferences exceeding 80 K ( 1 50 K in the case of toughened safety glass) . G lass is resistant to almost all chemicals apart from aggressive compounds such as hydrofluoric acid . In addition, ordinary glass surfaces can also be damaged by the alkali ne conditions formed under certain circumstances in hardened cement mortar. Manufacture

The high melting temperature of quartz sand (approx. 1 700°C) can be lowered to 1 2001 600°C when mixed with soda (Nap03) or potash (K2C03) ; fluorspar (CaF2) or sodium sulphate (Na2S04 ) reduce the formation of air bubbles . The semi-liquid glass is given the desired shape by flowing, blowing, pressing, casting or rolling while sti l l hot. G lass manufac­ ture requires enormous amounts of energy and is not environmentally friendly; however, the energy audit can be improved by mixing in bro­ ken g lass (cullet) from the production process and, to a l imited extent, from recycled material. Processing

G lass is cut to the desired size by scoring the surface. To do this, a cutting wheel made from diamond or high-strength steel is dragged over the surface while applying pressure. The pane of glass can be subsequently "snapped" along this l ine. Moistening the cut aids this procedure.

Glass parameters Density

[kg/m3 ]

Compressive strength

[ N / mm2]

> 800

Tensile bending strength

[ N / mm2]

30-90

2490

6-7

Mohs hardness Vickers hardness

[kN/mm2]

4.93 ± 0.34

Modulus of elasticity

[ N / mm2]

7x1 0'

Coeff. of thermal expansion

[ 1 0·6K]

8.4

Thermal conductivity

[W/mK]

0.8

Specific heat capacity

[J/kgK]

0.23

Transformation temperature

[OC]

525-545

Softening temperature

[OC]

7 1 0-735

Processing temperature

[0C]

1 0 1 5- 1 045

B 8.3

B 8.4

B 8.5

85

Glass

Metal oxide

Chemical formula

Iron oxide

FeO, Fe,0 3 FeO, Cr,0 3 Fe,03, CoO

deep blue

NiO

grey-brown

Nickel oxide

Colour

blue-green grey

Manganese oxide

MnO

violet

Copper oxide

CuO

red

Selenium oxide

SeO

pale red

Cobalt oxide

CoO

deep blue

Chromium oxide

Cr,0 3

light green

Silver oxide

AgO

yellow

Gold oxide

AuO

yellow

8 8.6

8 8. 7

There are two ways of fixing g lass: clamping or bolting. The clamping method is generally pre­ ferred because with suitable fixings this results in lower stresses in the glass. If fixin g s with bolts in drilled holes are employed, then it is important to ensure that the glass is mounted without any restraints. Washers help to d istrib­ ute the forces at the fixings over a larger area. Drilled holes and cut-outs must conform to m i n­ imum spacing and rad i i requirements.

can be varied between 1 .5 and 12 mm. The maximum d i mensions of single float glass panes are approx. 3.20 x 6.00 m (fig . B 8.9) . Today, some 95% of all flat g lass is produced by the float glass method . Float glass reheated to 640°C or more can be relatively easily bent over forms made from fire­ resistant material.

Special types of glass for building

Heat-resistant borosilicate g lass for fire-resist­ ant glazing has a higher silicon d ioxide content and in addition contains boron trioxide (BP3) ' Quartz g lass has a high silicon content, is especially heat-resistant, is pervious to ultra­ violet radiation and is ideal for photovoltaic modules. If lead oxide (Pb02) is mixed into the glass melt, this produces lead glass, which owing to its high optical density can b e used for lenses and simi lar optical apparatus. Nor­ mal, "clear" glass generally has a l i g ht green tinge and this can be minimised by reducing the amount of iron oxide (FeO) in the g lass melt to produce "colourless" or extra-clear glass. The use of metals and metal oxides to colour glass (fig. B 8.6) has been known since ancient times. Such oxides are introduced during the melting process and colour the whole body of the glass, not just the surface (body-tinted g lass).

Glass products

As the glass products (fi g . B 8.2) depend upon the production methods, the respective meth­ ods are described below together with their particular features. Float glass

Float glass is a high-quality, clear g lass with a flat surface. It is produced by floating the liquid glass at a temperature of 1 1 OO°C on a large bath of molten tin. Being l i g hter, the g lass floats on the surface, spreads out as far as the edges of the bath and gradually solidifies. So-called top rollers convey the glass out of the bath and at the same time reg ulate the thickness, which 86

Cast glass

Cast g lass, more correctly called rol led g lass, passes through pairs of cooled rollers and it is this process that gives this type of g lass its undulating surface. Like float glass it can also be further processed. It is suitable for applica­ tions such as greenhouses. The rolling process also enables a wire mesh to be incorporated (wired g lass) , which helps bond the glass fragments together in the case of damage. The g lass can also be g iven a pat­ tern on one or both sides (patterned glass) . Wired glass can satisfy the requirements for fire-resistant glaz i n g . Profiled g lass is a special form o f cast g lass. The edges of the glass are bent through 90° during rol ling to form glass channels. This product can carry considerable loads and is available i n standard widths of 232, 262, 331 and 498 mm; flange sizes between 4 1 and 60 mm are possible. Profiled glass provides the chance of producing endless ribbons of glass with horizontal retaining profiles alone (fi g . B 8.5). Glass tiles are cast g lass products available in sizes up to 640 x 7 1 5 mm, also in various col­ ours. They can be used both internally and externally.

8 8.8

Glass fibres and foam glass

G lass fleece and g lass cloth can be used to reinforce flexible sheeting, synthetic resins, screeds and concrete. G lass cloth is suitable as wallpaper and for bridging over cracks. Optical fibres of g lass are used for data transmission and in lighting systems. In accordance with their applications, foam glass (cellular glass) and g lass fibre insulating materials (glass wool) are discussed in the chapter " I nsulating and seal ing" (p. 1 36). Capil­ lary panels such as those used for transparent thermal i nsulation consist either of cellular glass structures, PMMA or polycarbonate (PC). These panels are translucent, approx. 8-40 mm thick and achieve U-values as low as 0.8 W/m2K with a simultaneous solar energy gain (see " Insulat­ ing and sealing", p. 1 40) . Glass ceramics

A temperature change in the glass melt trans­ forms this i nto a crystalline (ceramic) state and enables the production of glass with an espe­ cially low coefficient of thermal expansion. This type of glass is resistant to high temperatures (up to 700°C) and can therefore be used for cooker hobs or oven windows for instance.

Further processing of glass

This i ncludes working the edges, thermal treat­ ment or modifying the surface of the glass by various means. Edge work

There are four q uality grades for working the as­ cut edge (code KG) :

Pressed glass

Hollow glass blocks are produced by pressing two glass halves together. These very hard­ wearing building components can be bonded together with mortar and exhi bit good sound insulation properties. Pressing i s also used to produce transparent glass roofing tiles. All pressed glass products exhibit the typical marks that ensue where the two parts of the press come together.

Arrissed edges (KGS), produced by grinding chamfers. Ground edges cut exactly to size (KMG) in which the dimensions of the glass correspond exactly to the dimensions ordered. Ground edges (KGN) with a matt finish. Polished edges (KPO) have the same surface quality as the pane of g lass itself.

Glass

Thermal treatment (toughened safety glass, heat­ treated glass)

The thermal treatment involves heating the glass to approx. 600°C, then cooling the sur­ face in blasts of cold air, which ind uces a pre­ stress: tension in the core, compression on the surfaces. This type of treatment reduces brittle­ ness, improves crack behaviour and also increases the tensile strength. Toughened or heat-treated glass is therefore used for load­ bearing applications (fig . B 8 . 1 1 ) . One such type of glass is called toughened safety glass because it breaks into small, blunt fragments instead of large, sharp pieces when it breaks. Toughened safety g lass exhi b its a higher bending strength (fig . B 8 . 1 0) and better thermal stabi l ity. If intended for use as over­ head glazing or cladding to an external wal l , it must withstand a heat-soak test (see "The building envelope", p. 1 1 6) . The storage over several hours at approx. 300°C tests the glass for possible inclusions that could lead to failure once the glass is built into the structure. The cooling process is slower in the case of heat-treated glass. Heat-treated g lass has a lower internal stress and it breaks into larger pieces than toughened safety glass. However, in contrast to toughened safety g lass, heat­ treated glass in laminated form possesses a residual load-carrying capacity. Thin panes of glass for aircraft and lighting units are pretreated with a chemical method in an electrolytic bath. This method also creates a prestress and permits loads up to six times higher than normal glass. Surface treatments and coatings

Surface treatments can be for purely aesthetic reasons, but adding a coating to the surface of the glass can also change its properties. Enamelling Enamel is a coloured glass powder that can be melted onto the glass at approx. 700°C. This enables coloured surfaces to be produced which, depending on the thickness of the enamel, can vary from translucent to opaque. Any type of pattern, sign, etc. can be produced as required. The temperature rise during the enamelling process creates a prestress in the glass similar to that of toughened safety glass. Fusing This method involves fusing coloured pieces of glass into the surface of a single pane of glass. Glass treated in this way is suitable for i nterior use only. If required outside, the treated pane must be bonded to a pane of toughened safety glass with casting resin. Obscuring processes The mechanical treatments used are grinding or sand-blasting the surface of the glass. After this treatment the g lass is no longer transparent and has a matt appearance (fig . B 8.8). Certain areas can be masked in order to create pat­ tems as required. Etching with hydrofluoric

acid has a similar effect, but surfaces treated in this way do not attract so much d ust and d irt as sand-blasted or ground surfaces. Engraving is suitable for intermittent obscured portions. Silk-screen printing Silk-screen printing is used for decorating areas of g lass. Transparent, coloured surfaces and any form of decoration are possible (fi g . B 8 . 7 ) . Self-cleaning glass I n order to gain the maximum benefits from g lass in energy terms and to reduce the cost of cleaning the g lass, glass with self-cleaning sur­ faces has been on the market for a number of years. A coating of polymers prevents the for­ mation of water droplets and this prevents d i rt and dust adhering after the water has evapo­ rated (hydroph i l i c effect) . Other coatings func­ tion in a similar manner: the hydrophobic prin­ ciple uses a microscopically coarse structure to prevent the formation of a film of water (Lotus Effect) , and a photocatalytic coating breaks down organic residues with the help of the inci­ dent solar radiation. I n doing so, catalytic rad i ­ cals are formed in a chemical reaction and these destroy biological structures.

Max. producPermissible deviations tion size; side thk. side length x width length length < 2000 mm > 2000 mm

Nom. thk.

[mm]

[mm]

[mm]

[mm]

3

0.2

2

3

4500 x 3 1 80

4

0.2

2

3

6000 x 3 1 80

5

0.2

2

3

6000 x 3 1 80

6

0.2

2

3

6000 x 3 1 80

8

0.2

2

3

7500 x 3 1 80

10

0.3

3

4

9000 x 3 1 80

12

0.3

3

4

9000 x 3 1 80

15

0.5

5

6

6000 x 3 1 80

19

1

5

6

4500 x 2820

[mm]

B 8.9

Heattreated

Tough. safety

Property

Float

Ult. bend, strength

45

70

1 20

12

29

50

Max. permissible temp. 40

1 00

1 50

2.5

2.5

[ N /mm'} Max. bending strength [ N/mm'}

gradient [K} Density [g/cm3}

2.5

Cutting ability

Optically effective coatings Anti-reflection coatings reduce the reflection from the g lass surface. There are two ways of doing this. In one method several thin layers are applied to the glass and the effect of these is to cancel out the reflected radiation by means of i nterference. Such coatings can be applied for selected wavelengths. In the other method microscopic structures embossed in a layer of synthetic material reduce the refractive index of the glass. In contrast to the first meth­ od, such microscop i c surfaces work particular­ ly wel l at shallow i ncident angles. And the total incident solar energy is able to pass through the g lass. Dichroic coatings break up the incoming l i g ht at the surface of the g lass and allow the pane to shine i n various colours - based on interfer­ ence effects.

Failure behaviour

radial cracks emanat- dice-like­ ing from failure point

struct. B 8. 1 0

B 8.6

Metal oxides for body-tinted glass

B 8.7

Glass with silk-screen printing, health spa admin.

B 8.8

Acid-etched glass, art gallery, Bregenz, Austria,

B 8.9

Nominal thicknesses, permissible deviations and

building, Bad Elster, D , 1 999, Behnisch & Partner 1 997, Peter Zumthor maximum pane sizes for float glass B 8. 1 0 Comparison of the physical parameters of float, heat-treated and toughened safety glass B 8 . 1 1 Glass beams made from laminated safety glass, sunshading by means of baked-on ceramic ink, Museum of Glass, Kingswinford, UK, 1 994, Design Antenna

Laminated glass

The bonding of float, toughened safety or heat­ treated g lass over its full area opens up further possibilities for the use of glass regarding: • • · •

safety sound insulation fire protection visual design

Laminated safety glass

Lami nated safety glass is produced by bond­ ing together up to six panes with polyvinyl butyl (PVB) film. This transparent film binds the frag­ ments of glass together in the case of break­ age and ensures a certain residual load-carry­ ing capacity. Applications range from loadB 8. 1 1

87

Glass

Outside

Reflectio

coatings B 8 . 1 3 Louvre Pyramid, Paris, France, 1 989, B 8 . 1 4 Comparison of heat-absorbing and solar-control glazing B 8 . 1 5 Adaptive glass, "R 1 29" Project, Werner Sobek

III

J � U � I 11 I

Emission + convection

B 8. 1 2 Schematic diagram of position and effect of

leoh Ming Pei

Light permeability

======�>

-..___==>

___

1

1 2 3 4

0

Inside

Transmission

Emission

+ convection

2 3 4

Surface coating Low-e coating for thermal insulation Low-e coating for sun protection Surface coating B 8. 1 3

B 8.12

bearing (fig . B 8. 1 1 ) to bullet-resistant glazin g depending on t h e thickness. Fire-resistant glass

The use of aqueous gel layers as the interlayer instead of PVB film results in laminated fire­ resistant g lass. A rise in temperature causes the gel to foam up, which makes it opaque and therefore able to absorb heat radiation. D I N 4 1 02 d isting uishes between G-glass, which reduces the heat radiation by 50%, and F­ g lass, which must limit the temperature rise to 1 40 K on the side not exposed to the fire. Film interlayers

The use of, for example, printed polyethylene (PE) films i nstead of the PVB i nterlayer req uired for laminated safety g lass leads to further design options for architects. Very h i g h q uality printing is possible in any colour and any inten­ sity from transparent to opaque. This technique is limited only by the width of the films availa­ ble. Casting resin represents an alternative for bonding panes together. It is also possible to use laser imag i n g to create holographic optical effects. Like optical devic­ es such as lenses etc . , holographic optical ele­ ments (HOE) can generate specific red irection, refraction or shading of the incom i n g light.

Insulating glass

I nsulating glass consists of at least two panes on either side of an insulating layer of gas pre­ vented from escaping by a hermetic edge seal. Such composite glazing units improve the ther­ mal and sound insulating properties. All the types of glass described above can be com­ bined to form insulating glass elements. Further division of the cavity between the panes by means of extra glass panes or separating films can improve the insulating properties of the glazing still further. The cavity is generally between 8 and 20 mm wide. The hermetic edge seal must be designed according to the requirements of the gas fil l i n g . The g lued metal edge seal most commonly used consists of a double seal, a metal spacer and an integral dessicant.

88

Thermal insulation

I n comparison with s i n g l e g lazing, insulating glazin g achieves substantially better thermal insulation values. In physical terms, the heat transfer through the composite g lass unit involves three d ifferent processes: •

•

•

Convection, i .e. energy transfer by means of gas movements in the cavity Transmission, i .e . energy transfer by means of radiation Heat conduction in the g lass, g lass compos­ ite and cavity

Gas fillings Noble gas fillings such as argon, xenon or krypton improve the thermal i nsulation; com­ pared with air they lower the U-value (fi g . B 8 . 1 4) . Such heavy gases reduce the effects of convection and transmission in the cavity. Although xenon and krypton exhi bit better ther­ mal properties, argon is generally used owin g t o its ready availability a n d the simpler produc­ tion process. Vacuum Creating a vacuum in the cavity enables the heat conduction to be reduced even further. This requires a vacuum of about 1 0-3 bar in the cavity. The insulating effect of the vacuum does not depend on the spacing of the panes, which renders possible cavities < 1 mm wide. Howev­ er, as the vacuum causes the panes of glass to deflect inwards, spacers are necessary to pre­ vent them touching and hence negatin g the insulatin g effect. Coatings Metallic coatings of silver or titanium influence the reflective and absorption behaviour of the g lazing. The aim is to reflect the majority of the infrared radiation that is re-emitted out of the building. Such coatings reduce the emissivity and are in principle suitable for solar control and thermal i nsulation purposes. The spectral emissivity denotes that part of the transmission that penetrates a body by way of thermal emis­ sion. The emissivity of float glass is 0.89. There are three ways of applying such coat­ ings. In the online method a layer of metal

oxide is appl ied to the hot surface of the g lass d uring the manufacturing process. The offline process (including sputtering) involves coating the finished pane of g lass. A coating produced in this way is less durable than an online coat­ ing and is therefore immediately incorporated in an insulating glazing unit. The physical vapour deposition (PVD) method allows the coating material to condense on the glass. Heat-absorbing g lass coated with silver is known as low-e ( low emissivity) glass and represents the current state of the art. These days, such g lass can be produced practically without any colour. A low-e coating can cut the U-value of a glass pane from 3.0 to 1 .6 W/m2K. As the position of the coating influences the effect of the insulating g lazing (fig. B 8 . 1 2 ) , the g lazing units must be suitably marked to ensure that they are installed correctly. =

Heat-absorbing insulating glass This i s an i nsulating unit with at least one heat­ absorbing coating . It is normal for a heat­ absorbing double g lazing unit to achieve U-val­ ues of 1 .0-1 . 1 W/m 2K. Triple-glazed units with a noble gas fi lling and two low-e coatings can achieve U-values as low as 0.4 W/m2K. Solar-control glass

A reflective coating on the outer pane can lower the U-value considerably, improve the energy transmittance and hence contribute to controlling the amount of solar radiation enter­ ing a building. The type of reflection can range from simple mirroring to selective coating (e. g . inverse low-e coating ) . A s c a n be seen from fig. B 8. 1 4, it is necessary to check the colour rendering of the g lass when using solar-control coatings. Angle-selective coating Metallic coatings with a optical refraction behav­ iour dependent on angle represent a new devel­ opment. A m icroscopically small prismatic structure refracts the incoming light depending on the angle of incidence. Such coatings pre­ vent solar glare, but must be produced specifi­ cally for the location and the corresponding angle of incidence.

Glass

Solar-control glazing

Heat-absorbing glazing

Technical values of various insulating glazing units

Dimensions (pane/cavity/pane) [mm]

Double glazing,

Triple glazing,

Double glazing,

one pane coated

two panes coated

one pane coated

4-1 5-4

4-1 2-4-1 2-4

6-1 6-4

normal emission ,; 0.05

6-1 6-4 colourless 1

6-1 6-4

normal emission ,; 0.05

Argon

Argon

Argon

Air

Cavity filling (gas concentration ;, 90%)

Argon

Krypton

Argon

Krypton

blue 1

green

1

Uo

[W/m2K]

1 .5

1 .2

1 .1

0.8

0.5

1 .1

1 .1

1 .1

g

[%]

64

64

64

52

52

37

24

28

Light permeability 1

TL

[%]

81

81

81

72

72

67

40

55

Light reflection

RL

[ %]

12

12

g

14

14

1 1 /1 2 2

1 0/33 2

9/ 1 2 2

Ra

[%]

98

98

98

96

96

96/94 2

95/70 2

86/88 2

U-value to EN ISO 1 0077-1 Total energy transmittance

1

1

Colour rendering 1 1

Typical manufacturers' data

2 Values valid for inside/outside B 8.14

Adaptive glazing Variable coatings will be available for further applications in the future, particularly for intelli­ gent facades (fig. B 8. 1 5) . These coatings change - either automatically or by using suit­ able controls - from a light- and rad i ation-per­ meable to a light-deflecting, shading or reflect­ ing state. Electrochromic coatings consist of an approx. 1 mm thick polymer film containing certain metal oxides such as tungsten oxide (W0 ) , 3 nickel oxide ( N iO) or iridium oxide ( I r0 2) . The total energy transmittance of the glass is reg u­ lated by applying an electric current, which switches the glass between a transparent and a deep-blue state. After switching off the cur­ rent the latter state remains for a limited period (1-24 hours) . The coating achieves a reduction in the energy transmittance of max. 20%. Elec­ trochromic g lass is suitable for shading and anti-glare appl ications. Liquid crystals can be aligned upon applying an electric current and therefore switched from a light-scattering, non-transparent state to a transparent state. However, owing to their sen­ sitivity to temperature, liquid crystals have so far only been used internally for variable priva­ cy screens. Micro-encapsulated liquid crystals, which create a minimal obscuration of the glass, can vary the l i g ht transmission value between 0.48 and 0.76. Gasochromic g lazing represents yet another development. A coating of tungsten oxide (W0 ) changes to a blue colour due to an inlay 3 of catalytically generated hydrogen and loses this colour again when air is introduced. The coating enables the light transmission value to be varied between 1 5 and 60% . A gas supply capable of regulating an area of up to 1 0 m2 is required for operation. Phototropic and thermotropic g lasses do not require any form of control. The variabil ity of the phototropic glass is based on metal ions (e.g. silver ions) and the glass is regulated depend­ ing on the ultraviolet radiation. Thermotropic glass is based on a mixture of two substances that segregate above a certain temperature. The glass then scatters the incoming light and appears translucent.

Fittings in the cavity Glazing with rigid or movable fittings in the cav­ ity between the panes can satisfy further requirements with respect to thermal insulation, shading and aesthetics. However, it should be remembered that external pressure conditions d uring certain types of weather can cause the panes to deflect. It is therefore necessary to g uarantee sufficient clearance between the fit­ tings and the g lass. Light redirection, sunshading, anti-glare provisions Rigid or movable - with electric or mechanical drive - aluminium louvres can be fitted in the cavity. The surface of the louvres can be opti­ mised to red i rect the light; for instance, rigid reflective louvres are often triangular in shape with each side having a concave form. The incoming l i ght causes no glare provided the geometry has been chosen correctly; however, an unobstructed view through the window - in either direction - is no longer possible. Retro-Iouvres are very sma l l , folded, rigid blinds. Thanks to their ingenious geometry, they enable a good view through the window, achieve good light-redirection characteristics but also provide shad i n g . Besides movable a n d r i g i d systems i n the cavi­ ty, it i s also possi ble to i nstall any material whose degree of perforation determines the

energy transmission a n d t h e view through the window. The possibil ities are almost limitless: perforated sheet metal, woven metal meshes, wooden bars, etc. Sound insulation

Heavy gases, e . g . sulphur hexafluoride (SF6) , argon and krypton, also improve the sound insulation properties of i nsulating glazing com­ pared to a filling of air. The following parame­ ters can also improve sound insulation: • •

·

·

heavy panes (high inertia) different pane thicknesses (avoidance of resonance effects) inclusion of PVB films (mass-spring-mass principle) wide cavity

B 8.15

89

Synthetic materials

B 9. 1

B 9.1

The production of synthetic materials began in the middle of the 1 9th century with the chemi­ cal conversion of natural , organic raw materi­ als. Following an experimental phase, it became possible to improve specific properties of the materials in such a way that it was gradually possible to replace trad itional products. The chemical cross-linking (vulcanisation) of rubber­ latex from the rubber tree to form rubbery elas­ tic natural rubber marked the beginning of the rubber industry. Cellu loid , a conversion product made from nitrocellulose and camphor, is regarded as the first thermoplastic material. It was used as a transparent backing for the l i ght-sensitive lay­ ers needed for photography. U p until the end of the 1 9th century the produc­ tion of these synthetic products required regen­ erative raw materials. A chemical analysis reveals the carbon atom in the molecules to be the central, common element, which is added together to create the long chains that form the foundation for the structure of organic products. The application of this knowledge led in 1 898 to the production of the first ful ly synthetic mate­ rial from a combination of phenol (obtained from coal tar) and formaldehyde. Without fillers, phenolic resin is as clear as g lass. But mixed with fi l lers and pressed into moulds at high temperatures it provided the emerg ing electrical industry with a heat-resist­ ant, non-meltin g , non-conductive material for housings and insulation. This, the first thermo-

setting plastic, first appeared in 1 909 and was called Bakelite. Fundamental to the production of plastics is the fact that individual low-molecular units (mono­ mers) combine under suitable conditions to form macromolecules (polymers) in a chemical reaction known as synthesis. By 1 940 the plastics industry had devised methods for the large-scale production of most of the plastics we know today. The numerous combination options of various units and the further processing result in tailored materials such as foamed plastics, synthetic fibres or composites. These synthetic materials were i nitially used in the electrical engineering and automotive industries, but started to appear in the building industry from the 1 960s onwards - also for larger components. Since then, architects have dem­ onstrated the efficiency of synthetic materials for load bearing shell structures, facade clad­ ding or, for example, the translucent panels to the roof of the Olympic Stadium in Munich (fig . B 9. 1 ) . Today, synthetic products can be found in all branches of building ; either exposed e . g . as a floor covering or facade element, or con­ cealed, e . g . as waterproofing sheeting, insula­ tion or building services.

B 9.2

B 9.3

Tent roof covered with PMMA panels, Olympic Stadium, Munich, Germany, 1 972, Gunter Behnisch + Partner, Frei Olto and others

B 9.2

"Blow" PVC armchair assembled using seam welding, Italy, 1 967, Carla Scolari, Donato D'Urbino, Paolo Lomazzi, G ionatan d e Pas

B 9.3

"Connexion skin", pneumatic balloon made from PVC film assembled using seam weldin9, Austria, 1 968, Haus-Rucker-Co

B 9.4

Youth centre, Gironde, France, 1 994, Lacaton & Vassal

90

Synthetic materials

Chemical structure of synthetic materials

The fossil raw materials petroleum, natural gas and coal were formed by the decomposition of organic substances. Over m i l l ions of years, carbon (C) and hydrogen (H) accumulated on the seabed under the action of heat and pres­ sure. Petroleum consists of hydrocarbon molecu les whose boiling point rises as the length of the chain increases. The d istillation of petroleum in the refinery separates the molecular chains with their different lengths into ind ividual frac­ tions such as gas, petrol, diesel and heavy o i l . In the so-called cracking process unsaturated - and hence reactive - hydrocarbons are pro­ duced from the lightweight petrol (naphtha) obtained in the d istil lation process. Those hydrocarbons include the low-molecular gases ethylene and propylene, which are the most important raw materials for the manufacture of synthetic materials. Today, they can also be obtained from regenerative raw materials but only at great cost. Besides carbon and hydrogen, synthetic mate­ rials - depending on type - contain further chemical elements such as oxygen (0) , chlo­ rine (Cl ) , fluorine (F) , sulphur (S) , s i l i con (Si) and nitrogen ( N ) . Features

The following features are characteristic of the majority of synthetic materials, even if their properties are sometimes very specific: low density, low thermal conductivity, high coeffi­ cient of thermal expansion, high tensile strength, low modulus of elasticity, narrow con­ tinuous service temperature range, good elec­ trical insulation capabil ity, resistance to water and many chemicals, inflammabi l ity, ageing caused by ultraviolet radiation (unless add itives are used), brittleness at low temperatures.

Homopolymers consist of identical monomers, e . g . polyethylene (PE) , polystyrene (PS) or poly­ vinyl chloride (PVC). Copolymerisation i s the reaction between d is­ parate monomer units, which enables the prop­ erties of the synthetic materials to be varied even further. Copolymers with linear macromol­ ecules include, for example, styrene acryloni­ trile (SAN) and styrene-butadiene rubber (SBR). Step polymerisation Step polymerisation is achieved through the reaction of monomers with reactive groups usually hydroxyl (-OH) or amino groups (-NH2) - to form macromolecu les. In doing so, low­ molecular molecules, usually water (HP) , are given off. The reaction is based on an equilibri­ um, which allows the reaction to be controlled. Step polymers with l i near macromolecu lar structures are, for example, polyamide (PA) , polycarbonate (PC) and polyester (PET) , those with a cross-l inked structure include, for exam­ ple, phenol-formaldehyde resins (PF) . Chain polymerisation The basic principles of chain polymerisation are very similar to those of step polymerisation: different monomers form macromolecules through reactive groups; however, in this case without g iving off low-molecular by-products. The ensuing products are classified according to their chemical structure, e.g. as polyurethanes (PUR) or epoxy resins (EP).

The so-called polymer blends or alloys occupy a special position. These are blends of at least two complete thermoplastics, the aim being to benefit from the properties of both polymers, e . g . ABS + PC. Classification according to the macromolecular structure

The diverse range of synthetic products can be classified according to the method of synthesis or according to the molecular structure. Both forms of classification allow conclusions to be drawn regarding the nature of the raw materials used and the mechanical-thermal properties of the product.

I rrespective of the method of synthesis, there are three groups of synthetic materials classi­ fied according to the structure of the ind ividual macromolecu les and hence the possible arrangement withi n the polymer microstructure (fi g . B 9 . 7 ) . The degree of cross-l inking between the macromolecu les, which i nfluences

the fundamental properties of the synthetic materia l , is the governing criterion for this clas­ sification. Thermoplastics The macromolecules of the amorphous thermo­ plastics, e . g . polymethyl methacrylate (PMMA) , consist of l i near molecular chains that tangle around themselves but do not form any chemi­ cal bonds with each other. Amorphous thermoplastics are as transparent as glass and hard and brittle at room tempera­ ture. Partially crystalline thermoplastics such as polyamide (PA) also exhi b it orderly, so-called crystalline, regions in addition to the tangled reg ions, which contribute to the better strength of such materials. As the degree of crystallisa­ tion increases, so the transparency decreases. Physical bonding forces hold the macromole­ cules together. As the tem perature rises, so the bonding forces decrease and the flexibility of the i n d ividual chains increases, which allows the properties of the thermoplastics to gradually change from hard to thermoelastic to thermoplastic. The process ( e . g . melting) is reversible and can also be achieved with certain solvents. It is this characteristic that al lows the thermoplastics to be readily mou lded, machined and recycled. Elastomers Elastomers consist of cross-linked low-density molecular chains. Upon forming they are joined together chemically (vulcanisation) and cannot be separated again by applying heat, and therefore cannot melt. Solvents cause them to swell up. At service temperatures elastomers exhi bit a rubbery elastic behaviour and break down irreversibly at certain temperatures, e . g . elastomers o n the basis o f styrene-butadiene rubber (SBR). Thermoplastic elastomers (TPE) such as PUR or SBS block copolymers have similar proper­ ties to elastomers. However, they exhi b it physi­ cal i nstead of chemical cross-linking and can thus be processed l i ke thermoplastics. Thermosets The high-density, three-dimensional cross-link­ ing characteristic of thermosets comes about

Classification according to the method of synthesis

We distinguish between three methods for pro­ ducing synthetic materials. In these processes reactive monomers are combined through chemical reactions to form chain-like, branch­ ing or cross-linked macromolecules. Polymerisation Pressure, heat, light, initiators and catalysts ini­ tiate the polymerisation. The covalent bonds of the monomers break up and the i n d ividual units combine to form l i near molecular chains with­ out giving off any by-products. The external conditions influence the length of the chain and the degree of interlocking among the molecular chains.

B 9.4

91

Synthetic materials

as they are formed with pressure, heat or hard­ eners. After forming, the i nfusible thermosets can only be machined. They are hard and brit­ tle, insoluble in organic solvents and have the highest thermoforming resistance of the three groups of plastics. Their mechanical properties improve in conjunction with fibres or fillers. Reaction resins such as epoxy resins (EP) , polyurethane resins (PUR) and unsaturated polyester resins (UP) in the form of casting res­ ins or moulding compounds form the basis (matrix) for fibre composites.

a

Processing

The manufacture of monomers and their further processing to form polymers is carried out on a large industrial scale. This i n dustry supplies the pure synthetic materials in the form of granular material (pellets) to the product manufacturers. These then mix add itives homogeneously into the synthetic materials in the so-called com­ pounding process. Afterwards comes the form­ ing process to form the semi-finished or final product.

b

Additives

Besides the degree of polymerisation (length of chai n), degree of crystallisation and degree of branching/cross-linking of the synthetic mole­ cules, it is the additives that have a considera­ ble i nfluence on the properties of the synthetic materials.

B 9.5

Macromolecular structures of synthetic materials: a Tangling in amorphous thermoplastics b Low-density cross-linking in elastomers c High-density cross-linking in thermosets

B 9.6

Polycarbonate rooflights used as a facade ele­ ments, ads 1a gallery, Cologne, Germany,

2002,

b & k+

B

9.7

Systematic classification of synthetic materials according to macromolecular structure and method of synthesis

Fillers Fillers in the form of particles, fibres or beads made from organic or inorganic substances are used in thermosets as extenders, for i mproving the surface finish and for reducing the brittle­ ness. They can also influence the flowin g prop­ erties and the shrinkage of thermoplastics. The industry uses fillers such as cellulose, wood d ust, stone dust, chalk, kaolin or g lass beads . Reinforcing materials Reinforcing materials are used to improve the rigidity, strength and thermoforming resistance. Glass fibres (GF) , carbon fibres (CF) and ara­ mid fibres (AF) reinforce the synthetic materials in the form of meshes, non-woven fabrics or rovings in roofl i ghts, waterproofin g , vessels or pipes. Colorants I nsoluble colorants (pigments) dye the whole body of the synthetic material opaque. Soluble colorants are used in transparent, dyed syn­ thetic materials. Stabilisers The add ition of stabilisers can help to counter­ act the damage sometimes caused by heat, light and ultraviolet radiation. Besides its use as a pigment, carbon black also increases the UV­ radiation stability of many synthetic materials.

B 9.6

92

Plasticisers Plasticisers i ncrease the flexibility and hence also the impact toughness. Hard and brittle synthetic materials can thus be transformed into flexible materials. We distinguish between two types of plasticisation: external plasticisa­ tion is achieved by adding viscous, Iow-molec­ u lar substances which slip between the molec­ ular chains of the synthetic material , reduce the physical attraction forces and thus increase the flexibility of the molecular chains. As in this case the plasticiser is not chemically bonded with the synthetic material, in principle it can leach out, or be exuded, or over a long time in contact with another synthetic material can m ig rate to this other material. The original syn­ thetic material thereby loses its flexibility and becomes brittle. I nternal p lasticisation increases the spacing of the molecular chains chemically through copoly­ merisation and therefore increases the flexibility of the chain segments. I nternal plasticisation is virtually inert to external effects. Flame retardants The objective of flame retardants is to reduce the combustibility of synthetic materials. I n physical terms they bring about cooling o r pro­ vide a coating in the event of a fire, or - in chemical terms - form a layer of ash, or prevent the oxidation of combustible gases. Blowing agents Blowing agents create foams from synthetic materials. In the foaming process, blowing agents such as hig hly volatile fluids or com­ pressed gases are allowed to expand. In the chemical foaming process chemical reactions form gases (blowing agents) which then expand the polymers. Non-halogen blowing agents are now standard (see " I nsulating and sealing", p. 1 37 ) . Forming methods

The initial form i n g of semi-finished products or moulded parts from the basic synthetic materi­ als in powder, pellet or liquid form is known as "primary forming". In the case of thermoplastics the forming process is reversible owing to the physical entanglement. The melted pellets retain their form and cool down to the solid state. In thermosetting polymers a chemical cross-linking takes place during the irreversible forming process during which the thermoset­ ting properties ensue. Elastomers are irreversi­ ble after the forming process, but have a low­ density cross-linked structure produced by, for example, vulcanisation (fig . B 9.5) . Extruding The extruder turns the liquid thermoplastic syn­ thetic compound into PVC, PE, PM MA or PC sections, profiles, p ipes, boards, sheets, films, tubes and hoses in a continuous process. In a second stage, e . g . blow moulding, a section of tube, for instance, can be blown into a negative mould before cool i n g .

Synthetic materials

Synthetic materials

Thermoplastics,

Thermosets,

no cross-linking

high-density cross-linking

Polymerisation

Step polymerisation

Step polymerisation

Chain polymerisation

Polyolefins:

Polyamides (PA)

Aminoplasts:

Cross-linked poly­

Elastomers o n the basis

Polyurethane­

polypropylene (PP)

Polycarbonate (PC)

urea-formaldehyde resins (UF)

urethanes (PUR)

of:

elastomers (TPU)

styrene-butadiene rubber

Polyester elastomers

(SBR)

(TPC)

polyethylene (PE)

melamine resins (MF)

high-density

Linear polyester:

melamine-phenolic resins (MP)

polyethylene (PE-HO)

polyethylene terephtha­

resorcinol resins (RF)

butadiene rubber (BR)

Iow-density

late (PET)

& blends

chloroprene rubber (CR)

Epoxy resins (EP)

polyethylene (PE-LD) polyisobutylene (PI B)

Chain polymerisation

Elastomers on

isobutylene-isoprene

polyolefin basis:

Phenoplasts:

rubber / butyl rubber ( I I R)

ethylene-vinylacetate

phenolic resins (PF)

chlorosulphonated poly­

copolymer (EVAC)

Polyvinyl chlorides (PVC):

ethylene (CSM)

unplasticised (PVC-U)

Linear polyurethanes

Unsaturated polyester resins

ethylene-propylene-diene

plasticised (PVC-P)

(PUR)

(UP)

rubber (EPOM)

Polystyrene (PS) expanded polystyrene

Copolymerisation

(EPS)

Semi-synthetic materials Ethylene-tetrafluoro­

Polysulphone (PSU)

ethylene copolymer (ETFE)

Polyoxymethylene (POM)

Ethylene copolymer

Polyacrylonitrile (PAN)

bitumen (ECB)

Polymethyl methacrylate

Styrene acrylonitrile (SAN)

(PMMA)

Acrylonitrile-butadiene­

Silicones (SI) (polysiloxanes)

Polytetrafluoroethylene

styrene copolymer (ABS)

Nitrocellulose (CN)

Vulcanised

(PTFE)

Polyvinyl acetate (PVAC)

Cellulose acetate (CA)

fibres (VF)

Natural rubber (NR)

B 9. 7

Ca/endering A succession of rolls can turn thermoplastics or rubbers into sheet material. During this process it is also possible to profile the surface and incorporate a textile inlay. Floor coverings and waterproofing sheeting made from PVC or poly­ olefins can be produced using this method . Injection moulding The mass production of articles - but also small moulded parts - made from thermoplastics, thermosets and elastomers is possible with in­ jection moulding. The synthetic material is in­ jected into moulds under high pressure where it cools or cures. This method can also be used to interlock several plastic components. Pressing The moulding compound made from thermo­ setting resins is poured into the die and com­ pressed at a high temperature so that the molecular chains cross-link to form a thermo­ set. A lamination press is used for manufactur­ ing facings for boards and panels from backing sheets saturated with thermosetting resin. Thick-walled panels or foamed semi-finished products made from PS or PP (thermoplastics) are obtained by cooling after pressing. Rotational moulding Almost all thermoplastics are suitable for rota­ tional moulding . Rotation causes the fluid syn­ thetic compound to spread over the outside of the mould, which is rotated about various axes. This method is used to manufacture recepta­ cles for transport and storage.

Plastic forming Only semi-finished products made from ther­ moplastics (e. g . panels, sections, pipes) are suitable for plastic forming. Once heated to a suitable temperature they can be bent, stretch­ formed in a vacuum or deep-drawn. However, the new shape must be maintained until the product has fully cooled, otherwise the part returns to its former shape. Jointing Only semi-finished products made from ther­ moplastics (e.g. panels, sections, pipes) are suitable for plastic forming. Once heated to a suitable temperature they can be bent, stretch­ formed in a vacuum or deep-drawn. However, the new shape must be maintained until the product has fully cooled, otherwise the part returns to its former shape. Health hazards

Fully processed, pure synthetic materials are harmless when used properly. Even the manu­ facture, further processing or installation of syn­ thetic materials does not represent an increased health risk when carried out properly and pro­ vided the numerous reg ulations of the authori­ ties, e . g . the limits for concentrations of sub­ stances in the air or the technical directive for hazardous substances, are adhered to. Toxic compounds such as dioxins or furans can ensue during a fire. The halogen com­ pounds often used as flame retardants in some synthetic materials contribute to this problem (see "Glossary", p. 268 ) .

Recycling

The plastic waste that occurs during produc­ tion is generally returned to the material lifecy­ cle because it satisfies the conditions for reus­ ing the material: it is pure, clean and has not yet aged. There is no need for a complex and expensive collection system. There are basically four options for recycling plastic waste: Reusing the products Identical components in large batches plus compatibil ity guaranteed through standardised forms and dimensions ease the reuse of plas­ tics. This i s the case, for example, with returna­ ble bottles or moulded parts for the automotive industry. In the building industry only PVC win­ dow frames have been reused to date, and this only on a small scale. Enormous potential lies in expanding this system to include other com­ ponents such as facade panels or insulation by employing standardised sizes. Reusing the materials This involves the mechanical preparation of used plastics to form directly reusable ground materials. The chemical structure remains unal­ tered during this process. Viable reuse of synthetic materials requires an abundance of clean, sorted, plastic scrap cou­ pled with minimal logistics requirements. This is the case, for i nstance, with commercial p lastic waste or PVC windows and pipes from private household s . As a rule, the reuse of materials leads to a loss of q uality.

93

Synthetic materials

Reusing the raw materials To do this it is necessary to break down the polymer chains of the synthetic materials using heat and solvents. The ensuing prod ucts are petrochemical su bstances such as o i l s and gases which can be used to manufacture new synthetic materials or even for other purposes. This method also works with unsorted , soiled plastic waste. Reusing for energy purposes Plastics scrap and waste containing plastics have a high calorific value owing to their high carbon content. If they are unsuitable for recy­ cling processes to extract the materials or raw materials, they may be burned instead of fossil fuels for energy generation in appropriate incin­ eration plants. Thi s is frequently a rational option from both the ecological and economic viewpoints.

Synthetic materials in building

Alongside the packagings industry, the build­ ing industry is one of the most important cus­ tomers for products made from synthetic mate­ rials, accounting for about 20% of the output of the plastics industry. A selection of the synthetic materials used in building is given below, arranged in the order thermoplastics , thermo­ sets, elastomers and composite systems. Fig. B 9 . 1 3 l ists possible applications.

8 9.8

U n plasticised PVC (PVC-U) is hard and brittle. The add ition of plasticisers modify the material to form p lasticised PVC (PVC-P). PVC can be manufactured in clear transparent, coloured transparent or opaque forms. It does not ignite easily and burns only with difficulty owing to its high chlorine content. Polystyrene (PS) - thermoplastic

Polystyrene is clear l ike glass, has a high sur­ face gloss and is relatively brittle. Only by add­ ing UV-radiation stabilisers does it become hardweari n g . Solvent-based adhesives achieve a good joint by partly d i ssolving the surface. Foaming produces expanded (EPS) or extrud­ ed (XPS) polystyrene, both of which are wel l known a s thermal and sound insulation materials.

Polymethyl methacrylate (PMMA) - thermoplastic

Better known by its trade names, e . g . Perspex, this material has very good optical qual ities and a high scratch resistance. In many instanc­ es it can be used as a substitute for glass. Its high coefficient of thermal expansion must be taken into account, and unrestrained changes of length must be possible in the installed con­ dition. The following products are made from PMMA: clear transparent and coloured sheets, double-walled panels, rooflights and splinter­ proof panes. Polymers containing fluorine (PTFE/ETFE) thermoplastics

Polytetrafluoroethylene (PTFE) and ethylene­ tetrafluoroethylene copolymer (ETFE) both

Polyethylene (PE) - thermoplastic

Polyethylene is one of the polyolefins and con­ sists entirely of hydrocarbons. We d istinguish between high-density (PE-HO) and Iow-density (PE-LD) polyethylene. Polyethylene is an inex­ pensive, easily worked plastic and comes in forms from rigid to soft depending on the degree of crystallisation and polymerisation. In the form of a thin film, polyethylene is almost as clear as glass, but otherwise has a m i l ky white appear­ ance. It can be dyed any colour and i s very easy to join by wel d i n g . The applications in build ing i nclude drinking water and waste water p i pes, sheets for waterproofing and protecting, and floor coverings (see "Floors", p . 1 81 ) . Polypropylene (PP) - thermoplastic

The properties and applications of polypropyl­ ene - also one of the polyolefins - are similar to those of polyethylene. This synthetic material resists ageing without additives. Owing to its particularly high chemical resistance, its adhe­ sive qualities are poor. Polyvinyl chloride (PVC) - thermoplastic

The outstanding properties of PVC such as chemical resistance, mechanical strength, mul­ tiple machining options and adjustability with regard to flexib i l ity and impact toughness make it suitable for use in many areas, e . g . waste water p i pes, window frames, rooflights, corru­ gated sheets, facade elements, waterproofing and floor coverings. 8 9. 1 0

94

Synthetic materials

B 9.8

Coloured paper laminated with melamine resin, private house, Bad Waltersdorf, Austria, 2004, Splilterwerk

B 9.9

Translucent corrugated PVC sheets, workshop, Madrid, Spain, 2004, Garcia Abril

B 9. 1 0 "Falter", National Garden Exhibition, Kassel , Ger­ many, 1 955, Frei Olto B 9.1 1 Glass fibre-reinforced polyester resin, Forum Soft Pavilion, Yverdon-Les-Bains, Switzerland, 2002, Team Extasia B 9. 1 2 Glass fibre-reinforced polycarbonate, canopy, Kassel, Germany, 2005, Hegger Hegger Schleiff B 9.13 Possible applications for synthetic materials according to consumption (selection)

exhibit excellent chemical resistance. They are l ight-fast without the addition of UV-radiation protection, virtually self-cleani n g , exhibit excel­ lent thermal stability and incombustible. How­ ever, they are hydrophobic (and that makes them difficult to bond with adhesives) . Pneu­ matic, translucent constructions often make use of ETFE film, whereas PTFE is processed to form membranes in conjunction with textiles or as a coating to textiles. Epoxy resins (EP) - thermosets

The addition of a hardener causes the fluid or viscous molecules of the epoxy resins to cross­ link and form a thermosetting material. The strength and impact toughness varies depend­ ing on the fillers used, the degree of cross-link­ ing and whether fibre reinforcement has been incorporated. Coatings, adhesives and fibre composites are produced from epoxy resins.

B 9. 1 1

B 9. 1 2

adhesives for joining glass, metals, ceramics and plastics can be made from s i l i cones.

shells) make u s e of reinforcement made from g lass fibres (GF), carbon fibres (CF) and ara­ mid fibres (AF) . The latter two exhi bit very high tensile strengths but are seldom used owing to their high price. The quantity of non-woven fabrics, meshes, textiles and rovings i ncorporated l ies between 20 and 75% by mass. The combinations and the proportions of the individual components, the direction of the fibres, the elongation of the matrix at failure and the adhesion between fibres and matrix deter­ mine the properties of the composite material.

Fibre composites

Embedding fibres in synthetic materials im­ proves their mechan ical properties. Fi bre com­ posite systems consist of a base (matrix) of curing resins or thermoplastics plus a fibre material which is responsible for high strength, rigidity and thermal stability. The designations for fibre-reinforced plastics (FRP) are given in the order fibre-matrix, e . g . glass fibre-reinforced polyester resin (GF-UP) . The thermosetting materials suitable for use as a matrix are unsaturated polyester resins (UP) , epoxy resins (EP) and cross-linked polyurethanes (PUR) in the form of casting resins. Among the thermoplastics, polypropylene (PP) is just one of those that can be used for fibre composites. The building components with load bearing functions (e.g. structural sections, roofli ghts,

Synthetic materials made from regenerative raw materials

Owing to the enormous quantities of non­ degradable waste generated, our finite fossil resources and the high carbon d ioxide concen­ trations in the atmosphere, attempts are being made to produce synthetic materials from

Styrene-butadiene rubber (SBR) - elastomer

Owing to its extremely high wearing resistance, rubbery elastic behaviour and resistance to chemicals, SBR is ideal for floor coverings, waterproofing sheeting, seals and cable sheathing.

enc

0 "13 0) en 0> c

Silicones (SI)

Silicones possess simi lar features to plastics. However, instead of carbon atoms, inorganiC silicon atoms are responsible for forming the molecules. Owing to their chemical structure, silicones are designated as polysiloxanes (sili­ con-oxygen chains) , which exhi bit organic substituents (alkyl, vinyl and pheny l ) . On a commercial scale they are produced exclusive­ ly through polyreactions (e. g . step polymerisa­ tion) of low-molecular, sil icon organic com­ pounds. Depending on the length of the mole­ cule, this creates oily, resin- or rubber-type substances with outstanding resistance to high and low temperatures. The hydrophobic (water-repellent) behaviour of the silicone products and their consistent elas­ ticity during temperature fluctuations is exploit­ ed in sealing tapes and joint sealants made from siloxane elastomer (formerly silicone rub­ ber). Silicone resins are processed to form coatings and impregnations. I n addition , elastic

Applications of synthetic materials according to consumption

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0) L -0 50 K lead to changes in length of 3-5 mm/m depending on type of material and sheet thickness. Holes and fasteners must therefore be designed in such a way that fixing without restraint is guaranteed. Plastic sheets are fixed with conventional fasteners (fig. C 1 .3 1 ) . Corrugated sheets attached to walls are fixed through the troughs, and not through the crests as is the case for roof surfaces. Multi-walled sheets are normally installed with the voids ver­ tical in order to prevent condensation collecting.

C 1 .30 Profiled metal sheets a flat (E) b shallow ribs (L) c grooves (N) d micro-profile (M) e trapezoidal profile (T) f corrugated profile (W) C 1 .31 Methods of fixing various semi-finished products C 1 .32 External wall claddings using synthetic materials a corrugated sheets made from glass fibre­ reinforced plastic (GFRP), lit from behind b triple-walled polycarbonate panel, rear face co-extruded in different colour c transparent polycarbonate corrugated sheet revealing straw insulation behind d translucent polycarbonate double-walled panel with tongue and groove joints a

b

c

d

C 1 .32

1 15

The building envelope

a

b

Glass

loads for cleaning and maintenance must be allowed for on horizontal and sloping g lazin g ; dependi n g on thermal req u i rements, laminated safety g lass or a composite comprising lami­ nated safety g lass ( i nside) and toughened safety g lass is used. Laminated safety glass is also used for vertical safety barriers without any self-supportin g protective elements (handrail etc . ) . The corresponding technical regulations (e. g . TRAV) apply to vertical glazin g , the top edge of which is > 4 m above the adjoining level . Laminated safety glass can be used as single g lazin g , as the inner pane of an insulat­ ing glass unit, or as an outer pane with tough­ ened safety g lass on the inside. The load-carry­ i n g capacity can be verified either with calcula­ tions or by means of the pendulum impact test ( including the supporting construction) .

I n the architecture of the past few decades, the theme of transparency has played a dominant role, also as a signal for openness and commu­ nication. On the one hand, more slender and more l i ghtweight fixing systems, on the other, new glass technologies, have enabled archi­ tects to sound out the whole spectrum of possi­ bilities between transparent, translucent and opaque g lazing (fig . C 1 .33) , and at the same time have improved the thermal and optical properties. Besides the traditional frame, frame-less, sealed and overlapping forms of glazing have appeared. Furthermore, g lass facades with a ventilated cavity are becoming increasingly popular.

C 1 .33

Requirements

Glass facades have to satisfy numerous techni­ cal requirements. The incident solar radiation requires special attention. Exploited properly, solar radiation can contribute significantly to the energy requirements of a bu ildin g, and improve the comfort of occupants and q uality of the incoming l ight. On the other hand, solar radiation can lead to overheating, a poor interi­ or climate and to considerably higher energy and technical requirements and hence costs. For information on choosing the right type of g lass see "Glass" (pp. 86-89) . Safety Owing to the properties of glass, safety aspects may have to be considere d , depend­ ing on the particular application. The very spe­ cific way in which glass fai l s means that people must be protected against splinters of g lass falling from above, or prevented from falling through g lass barriers and spandrel panels. We distinguish here between overhead glazing (pitch > 1 0°) and vertical glazing . Only types of glass with sufficient residual load-carrying capacity may be used for overhead g lazin g . Supported along t h e edges, wired g lass can span up to 700 mm, laminated safety glass made from heat-treated glass up to 1 200 mm. Cut-outs in overhead glazing are not permitted. Other types of support and larger spans must be checked in each individual case. Additional

Areas of application

Glass facades have proved to be especially durable. I n terms of architecture, laminated and insulating glass - comprising various types of sheet g lass - enable many different types of surface finish (figs C 1 .36 c-f) . External wall cladding with ventilated cavity The facade cladd i n g products in widespread use include obscured g lass, body-tinted glass, glass with a coloured coatin g and patterned glass. Sandwich elements are also available, e.g. backing panels of expanded glass granu­ late with a coloured coating p lus toughened safety g lass on both sides. The requirements to be satisfied by a facade of toughened safety g lass with a ventilated cavity are stipulated in D I N 1 8 51 6-4. The structural analysis determines the thickness of the glass, but a nominal thickness of 6 mm is the mini­ mum permitted. All panes must undergo a heat-soak test prior to installation (see p. 87). A cladding comprising more than one pane requires a cavity at least 30 mm wide. Single-leaf glass facades Open or unheated interiors such as atria or conservatories require glass without a thermal break. As a free-standing wal l , such g lazing can also be used to satisfy sound i nsulation requirements. Heated interiors requ ire insulat-

C 1 .33 Pharmacology Research Centre, Biberach, Germany, 2002, Sauerbruch Hutton Architekten a vertical louvres open b vertical louvres closed C 1 .34 Fixings for glass a patent glazing bar with cap to clamp glass in place b individual clamp fixing c individual screw fixing through hole d structural sealant glazing (SSG) with mechani­ cal retainer C 1 .35 Systematic classification of glass facades C 1 .36 Glass facades with various types of glazing a cable net with overlapping panes b flush cable net c printed glass, individual fixings through drilled holes, loads transferred via spider brackets d glass printed with text, individual clamp fixings e printed glass, individual clamp fixings f double-leaf profiled glass facade

ing or heat-absorbing glass. The standard is double glazing with a system U-value (i.e. including the frame) of 1 . 1 - 1 .4 W/m2K. I n pas­ sive-energy housing triple glazing with a sys­ tem U-value of 0.7-0.8 W/m2K is normal. Build­ i n g s with high i nternal thermal loads or no external sunshadi n g can be protected against excessive solar gains (to a certain extent) by solar-control glass. G lass bricks and blocks achieve U-values as low as 1 .5 W/m2K, depending on type. They are installed with continuous mortar joints. Double-leaf glass facades Double-leaf g lass facades are used as part of a climatic building control system or for sound insulation purposes. In the case of sound insu­ lation, the inner leaf (insulating glass) provides the thermal break function, and the outer leaf is responsible for the sound insulation. Firstly, the pane of glass reflects part of the sound, and secondly, the cavity open to the outside cre­ ates oscillations that contribute - through inter­ ference - to the absorption of the sound waves (Helmholtz resonator). With an appropriate building height and a system of openings in the facade, such a system can also be used to provide protection from the wind. Translucent profiled glass, which can be built with (Jne or two leaves, represents a special form of external g lass wall (fig C 1 .36 f) . The glass channels are held on two sides by alu­ minium sections and bonded together with sili-

a

b

c

d C 1 .34

116

The building envelope

Glass facades

Rigid facade elements

clamped leaded light timber frame metal frame plastic frame profiled glass

clamping sections structural sealant glazing individual fixings

cone. Profiled glass is self-supporting up to two storeys. In a double-leaf arrangement, a U­ value of 2.0 W/m2K is possi ble, and with a fill­ ing of capillary-structure material this can be reduced to 1 .4 W/m2K. Forms of construction

The supporting structure has a decisive effect on the overall architectural impression of a glass facade. We d istinguish between com­ pression and tension systems. Systems in ten­ sion offer greater design freedom because the loads do not need to be carried at the bottom of the elements, but instead place increased demands on the structure.

Post-and-rail designs The most common form of construction is the post-and-rail facade. This consists of vertical primary members and horizontal secondary members - usually of aluminium, steel or tim­ ber. This form of construction enables all the loadbearing components to be sized accordi n g to the loads they have t o carry. The primary members can be loaded either in tension (sus­ pended) or in compression (supported). This form of construction requires the glass fix­ ings and seals or gaskets to be fitted on site, which calls for more generous tolerances. And as this type of design forces the panes of glass to be fitted from the outside, large, prefabricat­ ed facade elements are preferred in order to

screwed

side-hung vertical pivot

hopper top-hung horizontal pivot

push-out sliding

screwed bracket spider bracket

C 1 .35

offset the high cost of the scaffolding to a cer­ tain extent.

fore be ensured that all rainwater can drain away readily from all fixings and frames.

Framed designs I n contrast to the post-and-rail facade, the ele­ ments, mainly loaded in compression, are always mounted from the inside. Prefabrication results in better tolerances and better sealing . A continuous layer of insulation in the frame sections open to the outside can avoid thermal bridges.

Continuous support The panes of glass are held over their entire length by means of glazing beads or the wings/ caps of patent glazing bars. For instance, on a typical window frame the beads are fitted to the inside. Minimal widths of about 50 mm are thus possi ble. The further development of this form of clamping led to the patent glazing wings and caps (fig . C 1 .34 a) . These are mounted from outside, which allows both thermal problems to be red uced and also the fixing of two panes simultaneously. Patent glazin g wings/caps are max. 40 mm wide. This category also includes structural sealant glazing (SSG) . The structural bond between g lass and frame achieved with special sil icone adhesives results in completely flat facade surfaces broken up only by the joints, and with no fixings visible on the outside. In Germany this technique is not permitted above hei g hts of 8 m without add itional mechanical retention of the outer pane (metal sections).

Cable net designs The desire of architects to "dissolve" the glass facade more and more led to the development of the so-called cable net in the mid-1 980s (fi gs C 1 .36 a and b). The loads are carried by pre­ stressed cables. Such designs are primarily loaded in tension and req u i re strong abutments to accommodate the prestress in the cables. Fixing

Owing to the specific characteristics of g lass, it must be fixed in such a way that there is no contact between the glass and other hard materials, both when loaded or as a result of thermal movement. The glass is therefore sup­ ported on permanently res i l i ent intermediate pads or layers. We d isti n guish between inter­ mittent and continuous forms of support (fig . C 1 .35) . Water that cannot drain away properly leads to ponding, which can cause permanent "fogging" of the g lass. It must there-

Intermediate support I n this form of support the g lazing is fixed at individual points by clamp-like fixings or coun­ tersunk screws (figs C 1 .34 b and c). In princi­ ple, the clamping arrangement is better for the material because drilling through glass can lead to detailing problems. Discrete fixings in

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a

c

C 1 .36

117

The building envelope

drilled holes are usually attached to brackets called spiders. These metal components collect the forces from several glass support points and transfer them to the load bearing construction . Solar energy aspects

G lass enables the passive use of solar energy as it allows the solar radiation to penetrate into the building interior. However, glass is also a major component in active solar energy sys­ tems. I n order to minimise the transmission heat loss­ es in winter and the risk of overheating in sum­ mer, the passive use of solar energy requires the relationship between available solar radia­ tion, size of openings, heating requirements, shading systems and thermal storage masses to be balanced. I nstal l i n g solar energy systems in the building envelope converts the facade from a passive, protective enclosure to an active, energy-producing element. Generally, we distinguish between two active forms of solar energy usage: photovoltaic systems, for generating electricity (fig . C 1 .37) , and thermal energy systems, for generating heat. The archi­ tectural integration of these solar energy sys­ tems i nto walls and roofs results in the compo­ nents acting simultaneously as energy-produc­ ing, constructional , functional and architectural elements in the design of the building envelope. Photovoltaic systems There are currently two strategies for integrat­ ing photovoltaic systems into the facade. One of these strategies involves positioning the semi-transparent solar cells (the transparency of which is constantly being improved) in such

External wall claddings Layers • for origin of data see "Life cycle assessments", p. 1 00

a way that the g lass surfaces still possess a certain transparency. The other strategy employs opaque solar cells with d ifferent col­ ours in order to the increase the design options with this material. The cells - originally dark blue - are now avai lable in various shades of blue, red and green , also in a yellow-gold col­ ouri n g . The shape of photovoltaic modules employing vapour deposition techniques can be varied and thus used as a further architec­ tural device. The degrees of efficiency of photovoltaic modules are as follows: • • •

·

crystal l ine sil icon cells, 1 2-1 7%, amorphous s i l i con cells, 5 -7%, copper indium seleni d e (CIS) cells, approx. 1 1 % cadmium tel luride (CdTe) cells, 7%.

Thermal energy systems Developments in the field of thermal energy systems are following a similar pattern to those of photovoltaic systems. Thermal energy sys­ tems use air or water as the heat transport medium and were ori g i nally black, but now the range of colours includes shades of blue, red , brown, green, gol d , si lver a n d light grey. How­ ever, the new colours do not achieve the degree of absorption of the black material; the energy gains are reduced by 2 -1 0% depend­ ing on the colour. The degrees of efficiency of thermal energy systems are in the region of 50-75% for flat­ p late collectors, whereas vacuum collectors achieve values of up to 80% .

C 1 .37 C 1 .37

C 1 .38

PEI primary energy non-renewable [MJ]

PEI primary energy renewable [MJ]

suspended stone slabs, limestone'

1 68

17

limestone slab, cut, 30 mm stainless steel fasteners (V4A) , 1 40 mm

•

stone slabs bedded in mortar, limestone'

71

limestone slabs, cut, 20 mm lime-cement mortar MG 1 1 , 1 5 mm

•

Photovoltaic panels integrated into the building envelope, Mont-Cenis Training Academy, Herne, Germany, 1 999, Jourda & Perraudin, Hegger Hegger Schleiff Life cycle assessment data for external wall claddings

GWP AP ODP global acidificaozone warming depletion tion [kg C02 eq] [kg R 1 1 eq] [kg S02 eq]

EP eutrophication [kg PO.eq]

POCP Durability summer smog [kg C2H.eq] [a]

10

0.060

0.0030

0.0040

0

0

0

0

0.026

0.0020

0.0020

80- 1 00

0.0 1 9

;;, 80

Stone 0

80- 1 00

0

3.5

5.4 0

Materials with mineral binders in situ concrete

680

in situ concrete, reinforced, 2% steel (FE 360 8) , 1 00 mm concrete anchor, high-alloy steel, 1 20 mm

-

fibre-cement sheets'

88

five-cement sheets, 8 mm timber supporting construction, 30 mm

•

calcium silicate units, with ventilated cavity

320

calcium silicate units (KS Vb 20/1 .8) , mortar MG 1 1 , 1 1 5 mm wall ties, steel , 80 mm

-

118

36

55

0

0.21

0.Q1 5

c:=J

c::::::J

c::::J

38

3.4

0

0.030

0.001 7

0.0020

40-60

10

33

0

0.082

0.0086

0.Q 1 8

60-80

0

Cl

c::J

c:::::::J

The building envelope

External wall claddings Layers • for origin of data see "Life cycle assessments", p. 1 00

PEI primary energy non-renewable [MJ]

PEI primary energy renewable [MJ]

GWP global warming [kg C02 eq]

ODP ozone depletion [kg R1 1 eq]

AP acidification [kg S02 eq]

EP eutrophication [kg PO.eq]

POCP Durability summer smog [kg C2H.eq] [a]

facing masonry, with ventilated cavity

400

9

51

o

0.10

0.0053

0.0080

solid clay bricks (VMz 28/1 .8). mortar MG 1 1 , 1 1 5 mm wall ties, steel, 80 mm

-

o

o

o

0. 1 1

0.0053

0.0080

o

o

o

0. 1 5

0.0095

0.0 1 4

Cl

CJ

CJ

0. 1 5

0.0093

0.0 1 3

Cl

CJ

CJ

0.16

0.0097

0.01 3

o

CJ

CJ

0.20

0.014

0.0 1 8

CJ

=

=

Ceramic materials

ceramic panels, with ventilated cavity

285

VFH ceramic panels, 30 mm aluminium sections, 60 mm

-

50

21

o

=

o

60-80

;, 80

Glass profiled glass, single-leaf'

532

profiled glass (channel). 498 x 41 mm, glass 6 mm thick aluminium frame, silicone joint, 40 mm

-

toughened safety glass'

531

toughened safety glass, 6 mm patent glazing bar, aluminium, EPDM gasket, 40 mm

-

insulating glass Ug = 1 . 1 '

547

double glazing, argon filling, 24 mm patent glazing bar, aluminium, EPDM gasket, 40 mm

-

insulating glass Ug = 0.7"

837

triple 91azing, argon filling, 36 mm patent glazing bar, aluminium, EPDM gasket, 40 mm glass double facade

59

28

o

28

o

o

62 o

65 o

70

=

29

o

=

40

o

o

50-80

50-80

50

50

2 1 62

353

131

o

0.76

0.041

0.055

50

832

1 68

55

o

0.34

0.01 7

0.023

70- 1 00

0. 1 1

0.0075

0.010

60-80

o

o

o

1 .29

0.016

0.030

80- 1 00

0. 1 5

0.0075

0.0 1 0

70 - 1 00

o

o

o

0.12

0.0057

0.008

o

o

o

0.01 6

0.001 7

0.004

toughened safety glass, 6 mm aluminium supporting framework, 250 mm double glazing, argon filling, 24 mm Metal corrugated aluminium sheeting corrugated aluminium sheeting, 1 mm aluminium supporting construction, 30 mm

=

trapezoidal steel sheeting, coated

452

trapezoidal steel sheeting, coated, 0.75 mm galvanised steel supporting construction, 30 mm

-

copper sheet

1 091

9.6

24

o

41

60

0.000040

copper sheet with double welt standing seams, 0.7 mm particle board P5, 22 mm

c:=====rI D

titanium-zinc sheet'

416

sheet titanium-zinc with double welt standing seams, 0.7 mm particle board P5, 22 mm

_

stainless steel sheet'

319

43

25

33

19

0.00001 4

0.00001 1

stainless steel sheet with double welt standing seams, 0 . 7 mm _ particleboard P5, 22 mm

80- 1 00

Timber wooden shingles/shakes

41

226

red cedar shakes, single-lap tiling, 16 mm timber supporting construction, 48 mm

-21

o

=

weatherboarding

73

larch weatherboarding, dispersion glaze, 24 mm timber supporting construction, 30 mm

•

plywood

1 89

building-grade veneer plywood, 1 6 mm timber supporting construction, 30 mm

-

40-70

o

459

-43

o

0.029

613

-29

o

0.066 o

o

0.28

0.0 1 8

40-70

0.0034

0.009

o

D

0.0075

0.033

40-70

0.049

25

Synthetic materials plastic sheet

1 099

63

52

four-walled sheet, polycarbonate, 40 mm patent glazin9 bar, aluminium, EPDM gasket

o

=

For plasters, renders and thermal insulation composite systems, please refer to "Surfaces and coatings", p. 201 . C 1 .38

119

The building envelope

"00

'0 55

ft �

o o ��_________________

Thatch Reed, straw Flat overlap. elem. Stone slabs laid loose Wooden shingles/shakes Natural/fibre-cement slates Clay/concrete tiles Clay/concrete tiles Pro!. overlap. elem. Glass, plastic Flat sheets Profiled sheets Fibre-cement Metal Metal with welted joints Sheets Bitumen Flexible sheeting Plastics, rubber

Couple roof Framing in plane of roof Purlin roof Vertical framing with king post In situ concrete roof standard applications with additional measures

C 1 .39 Relationship between material and roof pitch C 1 .40 Green roofs, office building, Vienna, Austria, 2001 , Oelugan-Meissl C 1 .4 1 Systematic classification of materials according to principle of roof covering and roof waterproofing C 1 .42 Jointing principles: a overlapping flat elements b overlapping profiled elements c welted joints (sheet metal) d clamping of flat sheets e soldering of sheet metal f welding and bonding of flexible sheeting

C 1 .39

Roofs

The roof, as part of the building envelope and loadbearing structure, shelters the building and its occupants from the effects of the weather. It protects against precipitation, carries wind , snow and imposed loads, and is part of the thermal insulation system. There is a complex relationship between building utilisation requirements, types of construction and roof forms. This is illustrated by the many d ifferent types of roof influenced by cultural develop­ ments, regional materials, manual techniques and industrial developments, e.g. the thatched couple roof, or the industrially prefabricated flat roof. Design principles

The overall roof construction generally consi sts of various layers, each of which fulfils one or more specific tasks, e . g . wearing course, cov­ ering layer, waterproofing layer, load bearing layer (e. g . battens, boards) , ventilation cavity, insulation layer, loadbearing structure and inner lining. The schematic detailed drawings on p p . 1 22 ,

1 26 and 1 28 show typical examples of the above layers and the options for variations withi n the roof system. I rrespective of type of covering, material and roof pitch, we can d istin­ g u i sh between single- and double-skin roofs. Double-skin roof The double-skin roof is also known as a venti­ lated roof or cold deck. The typical characteris­ tic according to 01 N 41 08-3 is a ventilated air layer d i rectly above the layer of insulation (fig . C 1 .43) . This air layer g uarantees the removal of any water vapour from the interior that m ight d iffuse through the insulation. This concept only works if the cross-sectional size of the air layer is adequate and there is an uninterrupted flow of air between the inlets and outlets. Single-skin roof The sing le-skin roof is also known as a non­ venti lated roof or warm deck. The roof covering or waterproofin g lies immediately on top of the layer of insulation. A vapour barrier on the inside prevents water vapour reaching the insu­ lation (fig . C 1 .44) .

The disadvantages of the double-skin roof cor­ respond to the advantages of the single-skin roof as g iven here: •

•

•

• • •

The overall depth of the roof construction is reduced. The absence of an airflow means there is no accelerated heat transport. The roof construction is not subjected to any moisture, timber components do not require any chemical preservatives. Ventilation openings are not required. Fewer layers means simpler penetrations. All the building performance requirements can be integrated into one component (e.g . compact roof) .

Covering and waterproofing

The uppermost layer of the roof generally pro­ tects the building against preci pitation. Depending on the roof covering material and roof pitch, there are basically two ways of pre­ venting the ingress of preci pitation: fast drain­ ing from the building (pitched roofs) , or creat­ i n g a barrier and draining the water to prede­ fined points (flat and shallow-pitched roofs). This results in the terms defined in DIN 4 1 08: "covering" is a layer of overlapping compo­ nents, and "waterproofing" is the sealed bond­ ing of sheet materials. The denser the materials and the tighter their joints with one another, the shallower the pitch can be. Fig. C 1 .39 illus­ trates the relationship between material and roof pitch. Jointing principles

The primary classification of the materials for roof covering and roof waterproofing is carried out accordi n g to their form (fig C 1 .41 ) . Funda­ mental methods for jointin g , junctions and fix­ ing can be derived from this classification and explained by means of examples. The list of potential materials is constantly increasing due C 1 .40

1 20

The building envelope

Materials for roof covering and roof waterproofing

Roof covering

Thatch

Diminishing roof pitch Flat overlapping elements

Profiled overlapping elements

reed

wooden shakes/

clay roof tiles:

straw

shingles

pantiles

slates

flat pan tiles

fibre-cement slates

under- and over-tiles

asphalt shingles

Roman tiles French tiles

clay: wire-cut tiles pressed tiles bullnose tiles concrete roof tiles stone metal

interlocking pantiles interlocking flat pan tiles adjustable head lap tiles

Flat sheets

I I

L_ _ _ _ _ �

glass plastic

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ •

Profiled sheets

I I

Sheets

L_ _ _ _ _ �

corrugated fibre­

aluminium

cement sheets corrugated bitumen sheets corrugated plastic

lead

sheets

Roof waterproofing

Flexible sheeting bitumen

copper

synthetic materials:

stainless steel

thermoplastic/

galvanised steel

elastomeric sheeting

zinc

membranes

aluminium galvanised steel coated and galvanised steel copper stainless steel

concrete: Roman tiles double Roman tiles

C 1 .41

to regional differences and the appearance of new products. Overlapping joints Roof coverings consist of individual compo­ nents that are laid in an offset, overlapping arrangement so that they drain the rainwater. Together with an appropriate roof pitch, this type of joint results in a rainproof but not water­ proof roof. Additional layers provide further pro­ tective functions, e . g . against drifting snow and driving rain. •

•

·

Flat overlapping elements such as wooden shingles or clay bull nose tiles require a steep roof pitch because otherwise water can pass through the side joints and reach the layers underneath. Multiple overlapping both parallel with and transverse to the roof slope guaran­ tee that the water is drained reliably. Thatched roofs are based on the same, overlapping principle. Profiled overlapping elements have a form that prevents water penetrating the side joints. The simplest are the under- and over-tiles: the under-tiles (tegula) form a channel to drain the water, the over-tiles (imbrex) cover the space in between. Double Roman tiles and other special forms have interlocking ribs on one or more s i des, this enables shallower roof pitches because each tile covers the head, tai l and side joints and presents an effective barrier to water. Welted seams are used to join sheet meta l . The side joints o f the sheet metal lie above the water run-off leve l . The pieces of sheet metal are bent up and over (stand i n g seam) , or the bent-up edges are covered by an add itional strip of metal (batten roll seam) . The transverse joints are in the form of overlaps, welted seams and steps in the fal l , which drain the water reli­ ably. The principle of the welted seam is simi­ lar to that of the profiled overlapping element.

Sealed joints Roof waterproofing materials form a coherent waterproof layer. Large-format sheets, sheet metal and flexible sheeting have fewer joints and are thus suitable for sealed joints. ·

•

·

Flat sheets of glass and plastic or sandwich panels are joined together with metal sec­ tions. With the help of patent glazin g wings! caps and resilient gaskets made from syn­ thetic materials, they form a watertight layer. Sheet metals can be joined together and made watertight by solderin g , stai n less steel sheets by wel d i n g . Apart from stainless steel, this form of jointing is only suitable for smaller areas and elements because temperature­ related changes in length can cause restraint stresses. Flexi ble sheeting and membranes based on bitumen, synthetic materials and rubber can be bonded together to form watertight over­ lapping joints. Solvents d issolve the surface structure of polymers (solvent welding). Hot­ air or flame guns reverse the structure of the material so that it acts like an adhesive. These two techniques are used to waterproof roofs and basements reliably.

a

p

b

/

Roof covering c

Roofs > 5° pitch can be covere d . Every roof covering material is assigned to a range of roof pitches at which the material can be properly laid (figs C 1 .39 and C 1 .47) . Although the materials for roof coverings and external wall claddings can be identical, in order to emphasise the character of the enclos­ ing envelope, the roof surfaces are exposed to the weather to a greater extent than the walls. Accordingly, the materials for the roof coverin g must be o f a better qual ity s o that the roof can satisfy all requirements.

d

@L

•

e

C 1 .42

1 21

The building envelope

C 1 .43 Single-skin roof construction, pitched, covering of 6 4 Water

Water

/

o o o o o

o o o o

Heat

Vapour

2 3 4 5 6 7 8

Roof covering Separating layer Boarding Ventil. air cavity Sheathing Thermal insulation Vapour barrier Loadbearing structure C 1 .43

The local conditions led to d ifferent forms of roof over the course of the centuries. For exam­ ple, in reg ions with heavy snowfall, roofs must be conceived differently to roofs in windy areas. Likewise, even today the availability of regional building materials and the typ ical col­ ours dominate the appearance of whole roofs­ capes. Even social standing is reflected in the choice of roof form, either to give the buildings of important persons more prominence ( e . g . domes) or t o al low ideological viewpoints a form of expression. "Why do we have the p itched roof? Some peo­ ple believe it is a matter for romance and aes­ thetics. But that is not the case. Every roofing material demands a certain angle . . . . Apart from small tiles and sheets we had no other means of protecting us from rai n , snow and storms . . . . Of course, the best solution always seemed to be a roofing material consisting of just one piece. Such a roofing material would need only the angle necessary to allow the water to drain away naturally." (Adolf Loos: " D i e moderne Siedlung", lecture, 1 926) Roof forms The simplest form of pitched roof is the mono­ pitch roof, and a row of monopitch roofs pro­ duces a sawtooth roof. In Central Europe the duopitch roof - in the form of (close) couple and purl in roofs - is the most common form. The hipped roof is among the oldest forms.

o o

Heat

Vapour

2 3 4 5 6 7 8 9

Roof covering Tiling battens Ventil. air cavity Sheathing Boarding Ventil. air cavity Thermal insulation Vapour barrier I n ner lining C 1 .44

Curved roof forms such as barrel vault, dome and onion play special roles. Every roof form calls for the specific design of its constituent parts. Appropriate laying tech­ niques g uarantee a rainproof result, and there are even complete roofing systems with which manufacturers can provide solutions with differ­ ently shaped parts. These special parts form the edges of the roof surface (ridge, verge , eaves) and ensure that they function correctly. They also i ncorporate i nto the roof surface openings such as roof windows, chimneys and other penetrations. The recommended roof pitch is the lowest angle at which a certain type of roof covering has proved to be rainproof without fixi n g ele­ ments and special seals. Thatch

Reed and straw are laid in the form of long bundles with a d iameter of 1 40-1 70 mm. They are fixed to the horizontal battens with tyi n g wire and sways (small sticks) in individual, overlapping layers starting at the eaves and proceed i n g towards the ridge. No tying wire should be visi ble on the surface of the roof. The thickness of thatch is approx. 350 mm for reed, approx. 300 mm for straw (fi g . C 1 .46 a) . The chimney must pass through the ridge. Dor­ mer windows are roof openings that req u i re a steep pitch and rounded junctions to prevent ingress of rainwater. A double-skin roof con­ struction (pitch � 45°) prevents a build-up of

C 1 .45 1 22

sheet metal with welted joints (schematic) C 1 .44 Double-skin roof construction, pitched, covering of interlocking plain clay tiles (schematic) C 1 .45 Sheet metal covering, Pavilion, Zeewolde, Netherlands, 2001 , Rene van Zuuk C 1 .46 Various types of roof coverings: a thatch b natural slates c asphalt shingles d plain (bullnose) clay roofing tiles, double-lap tiling e profiled wire-cut interlocking concrete roof tiles f interlocking profiled (flat pan) clay roofing tiles g corrugated metal sheets, stainless steel h sheet aluminium with locked double welt standing seams

moisture and rotting of the covering. A thatched roof of reed will last between 30 and 50 years provided it is regularly main­ tained, constant ventilation is ensured and moss and pests are removed . Reed and straw belong to building materials class B3 (highly flammable). Wooden shakes and shingles

High-qual ity, slow-growing species of wood with fine growth rings (without sapwood) are used for producing split shakes or sawn shin­ g les. We disti n guish between nai ling and laying loose. Shakes/shingles for laying loose are 600-900 mm long, 70-300 mm wide and at least 1 5 mm thick. They are laid offset with an overlap and are wei ghted down with heavy stones, and are therefore only suitable for roof pitches of 1 7-22°. They shou ld be taken up, turned over and reversed, and relaid after 51 0 years. Nailed shakes/shingles can have a tapered or parallel form, are 1 20-800 mm long and 60350 mm wide. They should be m i n . 8 mm thick at the tai l . Nailed shakes/shing les are fixed to battens on counter battens with clout nails; fix­ i n g d i rectly to the loadbearing board ing is not recommended because there is no airflow under the shakes/shingles and that compromis­ es their durability. The durabi l ity of a double-lap tiling arrange­ ment of wooden shakes/shingles in years is roughly equal to the roof p itch in degrees, but 70 years is the maximum. A proper roof construc­ tion requires no chemical timber preservative.

The building envelope

Natural and fibre-cement slates

The clayey shale obtained from quarries is split into approx. 5 mm thick slates at the works. German slates have a blue-grey to black colour depending on the reg ion from where they are obtained . Other countries can supply red or dark green slates. Fibre-cement slates are nor­ mally grey in colour, but can be dyed or g iven a coloured coatin g . They are 4 mm thick. I n both these materials, components for the gen­ eral roof surface and roof edges are given their form in the works by milling or punching , by cutting to a template, or manually. Natural slates are normally supplied with holes, but can be supplied without. Fibre-cement slates are supplied with holes. The shape of the slate determines the form of roof covering: rectangular double-lap, diago­ nal, German (curved or scalloped, equal sizes ) , or Old German (scal loped, unequal sizes ) . The course o f slates are l a i d in a bond either horizontally or at an angle, on battens or board­ ing (fig. C 1 .46 b). They are fixed with nails, clips or hooks. The larger the ind ividual slates, the lower the pitch can be.

•

•

minimum overlap is determined by the spac­ ing of the battens. Two nibs on the underside of each tile prevent them slipping down the roof (fig . C 1 .46 d ) . I n crown tiling two rows of bullnose tiles are hung on every batten with a half-tile offset. The course on the next batten repeats the pattern of joints to g ive a straight line from eaves to ridge. I n slip tiling there is no offset between individ­ ual courses and 50 mm wide slips are placed beneath the side joints so that rainwater can­ not penetrate. The slips should not be visible on the roof surface.

In addition, all side and transverse joints can be "torched", i .e. filled with mortar, either from outside during lay i n g , or from i nside after­ wards. This mini mises the ingress of rai n , snow and dust and also bonds the clay tiles together. Clay tiles are usually simply laid on the roof construction. However, as the roof pitch increases, so wind suction has a greater effect and can lead to tiles uplifti n g . I n such cases it is necessary to fix the tiles with nails, screws or c l i ps .

Asphalt shingles

Also known as strip slates, these are basically the same material as flexible bitumen sheeting (see "Bituminous building materials", p. 64) and are 3-6 mm thick. A surface finish of coloured mineral granules or chippings provides protec­ tion against ultraviolet radiation. The shingles are available in formats of approx. 1 000 mm wide x 336 mm lon g . Two or three slits across the width gives them their shingle-like appear­ ance. Asphalt shing les are laid in a double-lap arrangement offset by half or one-third of an individual shingle and fixed with clout nails (fig . C 1 .46 c) . Self-adhesive strips (melted b y the action of solar radiation) on the top of the shin­ gles bond the shing les together. Asphalt shingles require a rigid supporting construction made from tongue and groove boards or wood-based boards. A layer of flexi­ ble bitumen sheeting nailed to the board i n g serves a s sheathin g . Asphalt shingles w i l l last about 3 0 years provid­ ed dust and dirt, which could form a substrate for plants, is cleaned off regularly. Flat overlapping clay roof tiles

Flat clay roof tiles are available without i nter­ locking ribs (bullnose tiles ) , with deep side ribs (wire-cut interlocking tiles) or with ribs on all sides (flat pressed interlocking ti les) (see "Ceramic materials", pp. 5 1 - 53 ) . The ribs pro­ vide an overlap in both d i rections. They deter­ mine the form of laying and the typical appear­ ance of the respective type of til i n g . When using clay roof tiles without any ribs, the tile size, roof pitch and type of tiling define the min­ imum overlap for the tiles. The following forms of tiling are used:

Flat overlapping concrete roof tiles

Concrete roof tiles are g iven a acrylate-styrene­ based coati ng to protect the concrete against the effects of the weather and mechan ical damage. Pigments can be added d uring mix­ ing to provide colour. The surface finish resem­ bles that of fired clay roof tiles. Flat concrete roof ti les have deep twin side ribs and tai l ribs, and the special elements for edges, roof pene­ trations, etc. match these. They are laid l i ke clay roof tiles; the format of the concrete roof tile determines the spacing of the battens and the overlap. Coverings of clay or concrete roof tiles do not req u i re any reg u lar maintenance. However, some care over the years (depend­ ing on the degree of soiling) will increase their longevity beyond 50 years, but junctions may require repairs in the meantime.

Bullnose tiles in double-lap tiling form a half­ tile bond. They are hung on batten s and the

r

-

,

..\l

�

�

.'

, �

IJ

e

J

!

I�

l'

,

Profiled overlapping clay roof tiles

The multitude of d ifferent clay roof tile shapes and their dimensions depend on the manufac­ turers - the standards specify only the require­ ments for the material itself (fig C 1 .46f. The same is true for concrete roof tiles. A general classification into basic forms is therefore help­ ful: •

·

• •

d

Clay roof tiles without i nterlocking ribs include under- and over-tiles, clay flat pan tiles and pantiles. If manufactured with nibs, these clay tiles can be laid dry d i rectly on the battens, or in mortar. Headlaps and side laps depend on the shape of the tile. On pantiles the right corner at the head and the left corner at the tai l are splayed to avoid a four-tile overlap at the corners. In the case of Roman and double Roman tiles and i nterlocking pantiles, it is the interlocking ribs that determine the direction of laying,

h 1 23

The building envelope

Building Max. materials load class [N]

Bending Tensile strength strength

Rec. roof pitch [0]

Weight per unit area [kg/m ']

Thermal conductivity [W/mK]

Water vapour diffusion resistance

Reedlstraw Wood shakeS/shingles (2-lap) Natural slates Fibre-cement slates Asphalt shingles (single-lap) Corr. fibre-cement sheets Corrugated bitumen sheets

;, 45 ;, 22 ;, 22 ;, 22 ;, 1 5 ;, 1 0 ;, 7

70 25 45-60 25-40 15 20-24

0.04--0.07 0.1 1 . 2-2 . 1 0.58 0. 1 6 0.58

1 /2 40 800/1 000 70/ 1 30 virt. vapourtight 70/ 1 30

B3 B2; B1 A1 A2 A2 A2 A2

Flat clay roof tiles bullnose wire-cut interlocking pressed interlocking

;, 40' ;, 35 ;, 25

60-75

1 .0 1 .0 1 .0

30/40

A1

;, 600 ;, 900 ;, 900

Flat concrete roof tiles with deep side rib

;, 25

60- 65

1 .5

60/ 1 00

A1

;, 800'

Profiled clay roof tiles under- and over-tiles pantiles interlocking flat pan

;, 40 ;, 35 ;, 30 ;, 22

gO

1 .0 1 .0 1 .0 1 .0

30/40

45 55 55

A1 A1 A1 A1

;, ;, ;, ;,

Profiled concrete roof tiles flat pan

;, 22

55

1 .5

60/100

A1

;, 800'

15 60 1 09 1 60-235 293-385

virt. virt. virt. virt. virt.

vapourtight vapourtight vapourtight vapourtight vapourtight

A1 A1 A1 A1 A1

470-700 270-500 ;, 1 50 90-230 200-300

virt. vapourtight

A1

270-500

Roof covering

Sheet metal (double welt standing seam) ;, 7 30 stainless steel ;, 7 30 galvanised steel 30 zinc ;, 7 25 ;, 7 aluminium copper 30 ;, 7 Metal sheets galvanised steel

;, 1 0

1 5 -30

60

[-]

[N/mm>] [N/mm>] 38-52 40-87 1 6 -28 1 6 -28 1 2 .2

1 000 1 200 1 200 1 200

8-30 8-30 8 - 30

8 - 30 8 - 30 8 - 30 8 - 30

, For crown and double-lap tiling: ;, 30 mm. , Depends on the cover width: ,; 200 mm cover width = max. load ;, 800 N; ;, 300 mm cover width = max. load ;, 1 200 N; intermediate values may be interpolated. 3 Owing to the specific material properties. the strength is measured differently (see "Bituminous materials". p . 65). C 1 .47

usually from right to left. Sometimes tiling with an offset bond and a variable head lap is possible. . Tiles with an adjustable head lap enable the overlap at the head of the tile to be varied by up to 30 mm despite the presence of head and tail ribs.

Precut splayed corners prevent four-sheet overlaps at the corners. The sheets are fixed to the supporting con­ struction with screws, at least four per sheet, through the crests of the corrugations. A seal­ ing washer/cap between fastener and sheet prevents ingress of water.

Profiled overlapping concrete roof tiles

Corrugated bitumen sheets

Concrete roof tiles cure after being moulded and hardly shrink during production (fig . C 1 .46e). I n some more elaborate forms of concrete roof tile, e . g . double Roman, the tail ribs interlock with the head ribs of the tile below and there­ fore can be laid dry while still attaining a good level of rainproofin g . They are laid in a similar way to profiled overlapping clay roof tiles.

Plain sheets made from cellulose fibres are impregnated with bitumen , shaped in presses and allowed to dry. Coatings on an acrylic resin basis give the sheets their colour and also help to protect the surface. The maximum size avail­ able is 2000 x 1 060 mm, and the sheets are 2.4- 3.0 mm thick. Edge and special compo­ nents p l us translucent corrugated sheets of PVC or g lass fibre-reinforced polyester resin are also available. Corrugated bitumen sheets are laid offset with the corrugations parallel to the slope so that rainwater can drain away easily. The side over­ laps are equal to one corrugation. The end lap of 1 40 - 1 60 mm depends on the roof pitch. The sheets are fixed through the crests of the corru­ gations with non-rusting nails with a PVC head, or countersunk-head nails with a sealing wash­ er. Run-off water that has drained across corru­ gated bitumen sheets can cause corrosion on unprotected metal parts, e . g . roof gutters, which must be avoided at all costs. The sup­ portin g construction of battens or boards must al low for ventilation of the sheets.

Corrugated fibre-cement sheets

Owing to their large format (up to 2500 mm long and 1 097 mm wide) , corrugated fibre­ cement sheets can provide a rapi d covering to roof pitches � 7°. They are divided i nto stand­ ard-pitch and narrow-pitch types. The latter have more corrugations than standard-pitch sheets (over the same width), but are not as deep. Special components for edges, junctions and special purposes (e. g . translucent sheets of glass fibre-reinforced plastic) complement the range of standard sheets. The sheets are laid starting at the eaves and proceeding towards the ridge, usually from right to left.

1 24

Profiled metal sheets

Profiled metal sheets can be made from galva­ nised, stainless or duplex-coated ( galvanis­ ing + powder coating) steels, aluminium alloys or copper. The shaping of the flat sheet metal, 0.5- 1 .5 mm thick, produces planar compo­ nents with various trapezoidal, corrugated or ribbed profiles, also metal panels. Composite panels are produced by enclosing insulating material between two metal sheets. The pro­ d uction process limits the width to about 1 200 mm, the length is limited by the transport restrictions. The side overlaps of these sheets are equal to one rib or corrugation. The fixing to the sup­ porting structure is by way of screws, rivets or c l i ps through the crests. Elongated holes and sliding fixings are used to accommodate tem­ perature-related changes in length. Additional sealing washers prevent the ingress of wind and water (fig . C 1 .46 g ) . =

Sheet metal

Flat sheets of aluminium, lead, copper, stain­ less stee l , galvanised steel and zinc are availa­ ble in rolls. The minimum roof pitch is 3°, but r is recommended because standing water can penetrate through the seams. Furthermore, as it evaporates, the water can leave behind aggressive substances on the surface of the metal. Rainproof side joints between the bays of sheet metal are ensured with single, double or locked double welt standing seams, or vari­ ous batten rol l s and, for sheet lead only, hol low or wood-cored rolls (fig . C 1 .46 h ) . All the differ­ ent types of side joints make use of the same bent-up edge, which can be bent by hand or machine. C l i ps fixed to the supporting con­ struction are fitted into the side joints to create a structural connection to the supporting con­ struction. Nevertheless, they sti l l permit chang­ es in length caused by temperature fluctua­ tions. The transverse joints are overlapped and welted. Sheet metal roof coverings are very durable (70 -80 years for copper, lead and stainless steel) and are suitable for shallow pitches and curved surfaces. The width of the sheets and the material chosen g ive the final roof surface its characteristic appearance. Double-skin roof constructions prevent a build-up of moisture below the vapour-tight metal covering. The supporting construction is usually made from timber boards.

The building envelope

Roof waterproofing systems

Flexible synthetic and rubber sheeting

Flexible bitumen sheeting

made from polymer­ modified bitumen

with thermoplastic elastomers Elastomer bitumen sheeting

with thermoplastic elastomers Elastomer bitumen sheeting

Polyisobutylene

Butyl rubber

Unplasticised polyvinyl chloride

Ethylene-propylene-diene rubber

Ethylene copolymer bitumen

Chlorosulphonated poly­ ethylene

Ethylene-vinylacetate terpolymer Chlorinated polyethylene

with thermoplastic materials C 1 .4 7 Physical parameters of roof coverings C 1 .48 Systematic classification of roof waterproofing systems

Plastomer bitumen sheeting

Roof waterproofing

Flat and shallow-pitched roofs require a water­ proofing or sealing layer because water cannot drain away quickly enough. This watertight layer covers the entire roof surface and includes penetrations and junctions. The sur­ faces of flat roofs can be used in many ways, e.g. as open landscaped areas, for parkin g , as circulation areas in urban surroundings (e.g. above basement parking), or as rooftop gardens. Flat and shallow-pitched roofs

The term "flat roof" is difficult to define precise­ ly. We can class roofs with a p itch 5: 5° as flat, and those with pitches up to 25° as shallow­ pitched. However, the German Flat Roof Guide­ lines speak of flat roofs with waterproofin g but without stating an angle. In order to avoid ponding, the fall of the roof should be at least 2%. Shallower falls must be regarded as spe­ cial constructions. The multitude of possible types of construction for flat and shallow-pitched roofs is due to the number of layers, which perform various func­ tions and together form that complex system known as a flat roof. Single-skin designs are favoured in practice. These can be classed according to the position of the roof waterproof­ ing within the system of layers. Conventional flat roof The waterproofing lies above the thermal insu­ lation. A vapour barrier must be i ncluded to protect the insulating material against moisture from the interior of the building. Depend i n g on the method of laying the waterproofin g , gravel can be used as protection against wind suc­ tion, heat and ultraviolet radiation (fig . C 1 .49) . Should any leaks occur, water tends to seep underneath the layers of the conventional flat roof.

made from elastomers (rubber sheeting)

made from thermoplastics (synthetic sheeting)

Flexible unsaturated poly­ ester resins Flexible polyurethane resins Flexible polymethyl methacrylate

Chloroprene rubber Thermoplastic elastomers

Alloys of flexible polyolefins

C 1 .48

Compact roof The compact roof is simi lar to the conventional flat roof. Cellular g lass slabs laid in hot bitumen serve as thermal i nsulation, and a vapour barri­ er is unnecessary. This plus the fully bonded flexible waterproof sheeting prevents any water seepi n g underneath. Upside- down roof I n this roof the insulation is laid above the waterproofing and therefore protects it against mechanical loads. The loosely laid insulating material should not absorb any water, and it is usually made from expanded polystyrene (EPS) . Grave l , stone/concrete flags or planting secures the insulating material against wind suction and upl ift. The roof waterproofing func­ tions both as drainage level and vapour barrier (fig . C 1 .50) . Duo-roof/plus-roof The duo-roof is a combination of conventional flat roof and upside-down roof. There are two layers of thermal insulation - one above and one below the waterproofing . If a roof is given a new layer of insulation ( e . g . in the case of add­ i n g rooftop plantin g ) , this is known as a duo­ roof. In the case of refurbishment work, this type of roof is known as a plus-roof when a new layer of waterproofing is laid on top of the exist­ i n g , insulated roof construction, and further insulation is laid on top of this.

Flexible bitumen sheeting

Bituminous sheeting consists of a backing soaked in straight-run bitumen and coated on both sides with a facing layer of blown bitumen. Sheeting made from polymer-modified bitumen uses strai g ht-run bitumen (including thermo­ plastic or elastomeric additives) for the facing layer and for soaking the inlays. Depending on the type of sheeting, a surface finish protects against ultraviolet radiation (see "Bituminous materials" , pp. 64-65). Bituminous sheeting is suitable for waterproofing roofs and basements. Laying Bituminous waterproofing can only claim to be permanently watertight when at least two layers are used, one on top of the other, which are bonded or welded together to form a homoge­ neous layer. The following methods have become establ ished in practice: ·

•

•

Flexible waterproof sheeting

Flexible waterproof sheetin g can be d ivided into bitumen, synthetic (thermoplastics) and rubber (elastomers) groups. Each group has its specific properties, resulting in different meth­ ods of working and different arrangements. Provided they are compatible, different types of flexible waterproof sheeting can be combined.

•

Pouring and rol ling: the (polymer-modified) bitumen sheeting is rolled out and pressed down into a hot bitumen compound that is poured ahead of the material. There must always be a continuous bulge of compound just ahead of the rol l of material. Felt torching: the underside of suitable sheet­ ing can be melted with a propane gas torch as it is unrolled and pressed down onto the roof surface. Mop p i n g : the hot bitumen compound can be spread over the roof before unrolling the sheetin g . There must always be a continuous bulge of compound just ahead of the roll of material. Cold a p p l i cation: self-adhesive sheeting has an adhesive appl ied to the underside of the sheeting by the manufacturer.

Depending on the type of roof construction, the first layer of sheeting can be fully bonded to the substrate or just with spots or strips of bonding

1 25

The building envelope

Water

1

compound. If mechanical fixings are being used , the first layer of sheeting is laid loose. Overlaps at all joints must be at least 80 mm. To avoid multiple overlaps at the same place, further layers are laid with a corresponding off­ set, but parallel with the first layer. From a material point of view, it is also possible to combine d ifferent types of flexible bitumen sheetin g , or to lay a combination of synthetic and bitumen sheetin g . However, compatibility between the d ifferent types must be assure d .

2 3 4 5

•

•

•

BV - bitumen-compatible NB - not bitumen-compatible P - plasticised K - lamination V - reinforcement E - inlay GV - glass fleece GW - glass cloth PV - polyester fleece PW - polyester cloth PPV - polypropylene fleece

o

1 2 3 4 5

Heat Vapour

Ballast Waterproofing Thermal insulation Vapour barrier Loadbearing structure

Flexible synthetic a n d rubber sheeting

C 1 .49 Water

1

2 3 4 5

,

Heat

o o

Vapour

,

/

Synthetic and rubber sheeting can be used for waterproofing roofs and basements. D I N 1 8 53 1 and 1 8 1 95 specify the materials, applications, dimensions and laying tech­ niques. Synthetic and rubber sheeting is made from thermoplastic and elastomeric materials respectively, with or without a backin g . Tear resistance, tear propagation, temperature-relat­ ed changes in length and how the sheeting adheres to the substrate are all influenced by the backing. Although sometimes referred to as a plastic fi l m , this is incorrect because films are max. 0.8 mm thick, and the thickness of this sheetin g is 1 -3 mm. Sheeting pre-joined at the works to cover a large area is also available.

·

•

•

1 2 3 4 5

Ballast Waterproofing Thermal insulation Vapour barrier Loadbearing structure C 1 .50

C 1 .49 Conventional flat roof (schematic) C 1 .50 Upside-down roof (schematic) C 1 .51 Roof waterproofing with flexible synthetic sheeting at pipe penetration C 1 .52 Physical parameters of roof waterproofing systems

Properties I n contrast to flexible bitumen sheeting, the synthetic sheeting is normally resistant to ultra­ violet radiation. In addition, it and its welded seams exhibit good root resistance. However, a single layer of waterproofing is vulnerable to mechanical damage, but this can be prevented by a layer of loose gravel with rounded grains ( 1 6/32 mm), or plantin g . A m u ltitude of prefabri­ cated special components is available, e . g . junctions for internal a n d external corners, roof vents, drainage outlets, etc. Such components ease the waterproofing of complex roof geometries. Some types of sheeting made from thermoplas­ tic materials are resistant to chemicals - with the exception of some solvents. They can be heated up and moulded in order to waterproof complicated details and junctions. Once the material cools, it sol idifies again. Owin g to their Iow-density cross-linked molecu­ lar structure, sheeting made from elastomeric materials has a rubbery elastic nature and can­ not be remoulded upon heatin g . However, its resistance to chemicals and solvents and its good d urab i l ity with respect to environmental influences make this a very d urable form of roof waterproofing . Types of sheeting A typical standardised sheeting designation would be D I N 1 6 734-PVC-P-NB-1 .5-V-PW. This describes the standard , type of material, specific properties, sheeting thickness in milli­ metres, sheeting make-up and type of inlay:

C 1 .5 1

1 26

Applications Owing to the multitude of different types of sheetin g , the manufacturers must specify prod­ uct-related properties and hence the applica­ tions. In principle, the following applies:

•

Non-laminated, unreinforced sheeting types without an i n lay are rarely used in practice. However, they are suitable for roofs with a complete, uniform covering (e. g . flags, grav­ el), bonded laying methods or for waterproof­ ing basements. A lamination on the underside of the sheeting improves the adhesion characteristics for full or partial (spoVstrip) bonding and can protect the sheeting against a rough substrate. The improved tear resistance of types of sheeting with a cloth inlay are suitable for use with mechanical fixings because the inlay diminishes the resilience of the sheeting. Fleece inlays likewise reduce the resilience. On roofs with a complete, uniform covering ( e . g . flags, gravel), sheeting with a fleece i nlay is usually preferred .

Laying Roof waterproofi n g with synthetic and rubber sheeting is usually carried out with just one layer of material. Separating layers between sheeting and substrate prevent chemical reac­ tions in the case of i ncompatib i l ity (e.g. between PVC sheeting and polystyrene insula­ tion or bitumen) . Fixing Mechanical fixings are suitable for sheeting with a high tear strength and for lightweight supportin g constructions. The mechanical fix­ ing comprises fixing bars or fasteners in the substrate consisting of fastener plus retaining washers. The fasteners are positioned at a reg­ ular spacing along the edge of the sheeting and are welded to the next piece of sheeting with an overlap. Continuous metal sections or strips are positioned at the necessary spacing and covered with additional strips of sheeting approx. 200-250 mm wide. The number of fix­ ings depends on the wind suction loads calcu­ lated. Full or partial bonding is carried out with hot bitumen and polyurethane adhesives, which bond the sheeting to the substrate. In the case of bituminous adhesives, the bitumen compatibility must be checke d . Some types o f sheeting a r e manufactured with a self-adhesive coating on the back for full

The building envelope

Flexible sheeting

Bitumen Uncoated bitumen-saturated sheeting Bitumen roofing felt with felt inlay Bitumen roofing felt with glass fleece base Bitumen sheeting for waterproofing of roofs Bitumen waterproof sheeting for felt torching with jute cloth with glass cloth with glass fleece with polyester fleece Flexible bitumen sheeting with metal inlay

Abbreviation

DIN

Service temperature [OC]

R 500 N R 500 V 1 1 ; V 13

52 1 29 52 1 28

0-70 0-70

Max. tensile force [N] long. trans.

Max. elongation Min. tearing Elongation strength [N / mm>] at tear [%] [%] trans. long. trans. long. trans. long. 1 .5 2 2

1 .5 2 2

350 300 400

200 200 300

600 1 000 400 800 500

500 1 000 300 800 500

2 2 2 40 5

3 2 2 40 5

1 000

1 000

2

2

800

800

40

40

200

200

1 50

1 50

52 1 30;

J 300 DD; J 300 84; J 300 85 G 200 DD; G 200 84; G200 85 V 60 84 PV 200 DD; PV 200 85 Cu 0.1 0; AI 0.2 0

Polymer-modified bitumen Polymer-modified bitumen sheeting­ for waterproofing of roofs Polymer-modified bitumen waterproof sheeting for felt torching with glass cloth PYE-G 200 DD; PYE-G 200 84; PYE-G 200 G5; PYP-G 200 84; PYP-PV 200 85 with polyester fleece PYE-PV 200 DD; PYP-PV 200 DD; PYE-PV 200 85; PYP-PV 200 85 Cold-applied self-adhesive K8K bitumen sheeting

52 1 3 1

1 8 1 90-4

0-70

0-70

52 1 32 52 1 33 (PYE) - 25 - 1 00; (PYP) - 1 5 - 1 30 1 8 1 95-2

Thermoplastics Ethylene copolymer bitumen Ethylene-vinylacetate Chlorinated polyethylene Polyisobutylene Polyvinyl chloride, unplasticised

ECB EVA PE-C PIB PVC-P

1 6 736 1 6 731 1 6 730

depends on depends on depends on depends on depends on

Elastomers Chloroprene rubber Chlorosulphonated polyethylene Ethylene-propylene-diene rubber Isobutylene-isoprene rubber

CR C8M EPOM IIR

7864 1 6 733 7864 7864

- 20 to 70 - 20 to 70 - 20 to 70 - 20 to 70

1 6 732

product product product product product

3 - 3.5 4-10 12 4.5 10-18

3-3.5 4-10 12 4.5 1 0 -1 8

400-600 300-500 > 330 350 250-360

8.5 13 5 - 9.8 7.5-8

6.9 15 5-9.8 7.5-8

280 280 > 550 > 800 350-540 350-540 > 450 > 450

400-600 300-500 > 330 350 250-360

C 1 .52

bonding to the substrate. Roof waterproofing beneath a complete, uniform covering (e.g. planting, gravel) can dispense with fixings and bonding provided the load of the covering can withstand the wind suction forces. Jointing The quality of the overall roof waterproofin g depends on t h e quality o f the seams. This calls for careful cutting of the sheeting (especially at the edges) , avoiding folds, creases and ten­ sion, and ensuring that the sheeting is turned up 1 00-1 50 mm above the top of the roof fin­ ishes at all junctions and terminations. Sheeting made from thermoplastic materials can be connected homogeneously with suita­ ble solvents (solvent welding. In doing so, the overlap should be approx. 50 mm, depending on the type of fixing (min. 30 mm for a welded seam) . Hot air (temperature at nozzle approx. 600°C) can be blown into the overlap to weld the sheeting together. Using a roller, the softened sheeting is then pressed together to form a welded jOint min. 30 mm wide. Heat fusing with a heat gun uses the same principle. Owing to their cross-linked molecular structure, sheeting made from elastomeric materials can­ not be welded (exception: partially cross-linked

CSM and some other materials) . I nstead , a con­ tact adhesive is spread over the surfaces to be joined and once the adhesive has gone off, the sheeting is pressed together with a m i n . 50 mm overlap. Hot vulcanising is suitable for off-site prefabrication. The seams produced using this method have the same properties as the sheet­ i n g itself.

Roofs for circulation

Waterproofed surfaces on buildings and civil engineering works can be used as circulation areas (e.g. flat roofs and basement parki n g ) . Besides the structural load-carrying capacity, they require a suitable finish that is not con­ nected directly to the structure and also pre­ serves the flexible sheetin g . An upside-down roof can be used to provide permanent protec­ tion for the high-quality flexible sheetin g . Finish­ es for roofs with foot traffic can be d ivided into three groups depending on type of layin g , type of jointing and the contact with the roof water­ proofing. Permanent finishes Cement screeds, asphalt and flags in mortar are among the permanent roof finishes. I n

order to avoid stresses, movement joints must be i ncluded at certain intervals. The finishes must be laid to a fal l of � 1 .5% so that surface water can drain readily. Loose finishes Like in the building of footpaths, flags (e.g. con­ crete or stone) and paviors (e.g. concrete, stone or timber) can be laid in a bed � 50 mm thick that allows some movement. The bed con­ sists of sand (risk of washing out, poor water seepage) or fine gravel or chippings separated from the layer of sand by a non-woven fabric fil­ ter. The advantage of this is that it allows some of the water to seep away. An additional drain­ age mat carries the seepage water to gutters or outlets. It i s not essential to lay the finishes to a fal l . Raised finishes I n this case a finish of stone/concrete flags of timber is raised above the roof waterproofing. Provided the underlying layers have sufficient compressive strength, the advantages of this type of construction are its low self-weight, q u ick installation and absence of fal l s because the water simply drains through the open joints onto the roof waterproofing below and from there flows to the concealed outlets. Simple

127

The building envelope

(fig . C 1 .55). Such plants demand specific sub­ strates and thicker layers, and they must be constantly cared for and watered. Layers

Heat

1 2 3 4

o o

Vapour

Plants Plant-bearing layer Filter fleece Drainaqe laver

if required 6 Waterproofing 7 Thermal insulation 8 Vapour barrier

C 1 .53

sawn timber is used under the uprights, or mor­ tar sacks or height-adjustable supports with an X-joint. Numerous systems are avai lable on the market.

Green roofs

By adding landscaping and plantin g to roofs, it is possible to gain multiple uses from roofs over private or public areas. Besides the aesthetic aspects, the areas of greenery and planting can provide leisure and recreation zones. From the ecological viewpoint, landscaped surfaces on structures improve the microclimate of the urban environment by evening out temperature peaks, increasing the humid ity of the air and bonding dust and d i rt better than gravel-cov­ ered roof surfaces. Furthermore, areas of p lant­ ing protect the roof waterproofing against u ltra­ violet radiation. Owing to their layer of vegeta­ tion, green roofs are classed as combustible. They must therefore satisfy requirements regarding distances from neighbouring build­ ings and they require incombustible thermal insulation. The additional layers for the planting increase the thermal insulation effect and func­ tion as a basin for retaining precipitation water - they store the water and release it again later. Flat and shallow-pitched roofs up to approx. 25° are suitable for planting. The steeper the slope, the greater is the work req u i re d to retai n the water a n d prevent slippage. We d istinguish between extensive and intensive rooftop plant­ ing irrespective of the function of the area.

Starting with the standard construction of the single- and double-skin roof, further layers are added in order to meet the req u i rements for a green roof. Sometimes ind ividual layers provide more than one function, in other cases not all functions are req uire d . The sequence of layers from outside to inside is, in principle: plants, plant-bearing layer, filter, drainage layer, pro­ tection mat, root barrier, separating layer, waterproofing (fig . C 1 .53) . Basically, it is also possible to add planting to an upside-down roof. Plants Moss and sedum varieties plus many plants that seed themselves or form shoots spread out over the roof surface according to season and weather conditions. A permanently green sur­ face can only be achieved with intensive rooftop planting, which is then akin to a garden.

layer because such particles would impair the drainage function. If the grains of the plant­ bearing layer are coarse and those of the drainage layer fine, the drainage layer act as a filter. Loose mineral materials, boards and non­ woven fabrics (PA, PP, PET, glass fibre or rock­ wool) are available for use as filters. Drainage layer The excess water seeping down from the plants is carried away to outlets and g utters via the drainage layer in order to avoid a build-up of water. At the same time, the drainage layer has the task, through a medium pore size, to store some of the seepage water for the plants. Roots then penetrate the drainage layer. It cor­ responds to the natural subsoil and can be classified in a similar way to the plant-bearing layers: •

•

Plant-bearing layer The plant-bearing layer (substrate) has the task of storing or draining water, retaining nutrients and providing a firm hold for the roots of the plants. The thickness of the layer, the particle size and form, the constituents and its water retention capacity determine the plant varieties that can be planted. On pitches � 1 5° a vegeta­ tion mat prevents erosion of the substrate . The different plant-bearing layers are classified according to form and composition: ·

•

•

loose materials with varying organic and inor­ ganic proportions and porous structures, e . g . mineral-organic soil mixes, humus, lava mixes, pumice, expanded clay slabs of mineral wool or mineral-enriched polyurethane foam mats of natural and synthetic fibres together with loose materials

•

Depending on the roof pitch, uncrushed (

25

>

20

25 25 25

>

20

>

25

>

20

> >

0 0 0 0

0 0

> >

20 25

C 1 .59 Physical parameters of membrane materials C 1 .60 PTFE-coated glass-fibre cloth, carport, municipal waste management depot, Munich, Germany, 1 999, Ackermann & Partner

C 1 .59 C 1 .61 ETFE foil cushions, Allianz Arena, Munich, Ger­ many, 2005, Jacques Herzog & Pierre de Meuron C 1 .62 Life cycle assessment data for roof coverings and roof waterproofing systems

Applications and properties

Material categories

Membranes can be erected considerably faster than conventional roofs because the material is cut to size and all the edges are prepared prior to delivery. Owing to the low weight of 200-1 500 g / m2, movable roofs like the tennis court at Rothen­ baum, Hamburg, Germany (see Example 25, pp. 261 -63) , and long-span structures free from intervening columns can be erected. Multi-layer membrane systems satisfy add ition­ al thermal insulation criteria (U-values from 2 . 7 down to 0.8 W/m2K); they also improve the sound insulation. Transparent films have a higher UV radiation permeability than glass, which can be an advantage for indoor swimming pools and greenhouses. Multi-layer, pneumatic, prestressed membrane constructions made from films (cushions) pro­ vide thermal insulation in conjunction with good translucency and transparency. In a three-layer arrangement the pneumatic adjustment of the middle layer results in different degrees of l i g ht transmission when the middle and u pper mem­ branes are printed with offset l i g ht-reflective patterns. Membrane systems for the active use of solar energy are currently undergoing development.

Membrane materials can be classed as water­ tight, closed-pore, and water-permeable, open­ pore materials because the watertightness is usually the primary application criterion.

130

C 1 .60

Closed-pore materials The technical properties of PVC-coated polyes­ ter cloth and PTFE-coated g lass cloth enable them to be used externally as protection from the weather. PVC-coated polyester cloth with various surface finishes is suitable for movable and reusable membrane constructions thanks to its good buckl i n g resistance. It is not read ily flammable and, at 1 5 -20 years, relatively long­ lastin g . PTFE-coated g l ass cloth is incombusti ble and will remain serviceable for more than 25 years. It has a self-cleaning surface and owing to its coatin g does not absorb any moisture. The translucency can be controlled between 0% and 50% by adjusting the density of the cloth and the thickness of the coating. However, it is less elastic and less resistant to creasing than PVC-coated polyester cloth . Factors such as draft desig n , structural calcu­ lations and functional requirements determine the choice of material just as much as the anti­ cipated module sizes. PVC-coated polyester

C 1 .61

cloth can be prefabricated in sizes up to 1 0 000 m2. By contrast, owing to the handling during production, PTFE- or ETFE-coated glass-fibre cloth is available only in sizes up to 2500 m2. Together with ETFE films, PTFE- or ETFE-coated glass-fibre cloth and PVC-coated polyester cloth account for approx. 90% of all membrane constructions. The d urab i l ity of ETFE films is about 25 years. They are primarily used for pneumatic, trans­ l ucent constructions and are readily printed. Their high shear strength calls for very precise cutting during fabrication to create irregular and curved shapes. THV film (tetrafluoroethy­ lene hexafluoropropylene vinylidine fluoride copolymer) has a lower tear strength but is more elastic and easier to work. The elongation behaviour of PVC film varies considerably with the temperature and this film also has only a low strength. It is therefore used for internal applications only. Open-pore materials Uncoated PTFE cloth is ideal for movable con­ structions that do not have to be rainproof, e . g . folding membranes for shading systems. Cot­ ton cloth can be used temporari l y both internal­ ly and externally. The swelling behaviour of cot­ ton once it is wet provides the necessary rain­ proof effect. I nterior acoustics can be influ­ enced by using micro-perforated membranes made from cloth or film.

The building envelope

Roof finishes Layers ' for origin of data see "Life cycle assessments", p . 1 00

Roof coverings

flat plan tiles, titanium-zinc flashings

clay flat pan tiles, 20 mm timber battens, 24 x 48 mm polyethylene (PE-HO) sheathing, 0.5 mm concrete tiles, titanium-zinc flashings

concrete tiles, 20 mm timber battens, 24 x 48 mm polyethylene (PE-HO) sheathing, 0.5 mm titanium-zinc sheet

titanium-zinc with double-welt standing seams, 0.7 mm timber boards, 24 mm copper sheet'

copper sheet with double-welt standing seams, 0.7 mm timber boards, 24 mm

fibre-cement sheets', titanium-zinc flashings

corrugated fibre-cement sheets, 8 mm timber battens, 24 x 48 mm polyethylene (PE-HO) sheathing, 0.5 mm MOF board, 1 8 mm natural slates', copper flashings

natural slates, Old German slatin g , 5 mm flexible bitumen sheeting type V 1 3, 5 mm timber boards, 24 mm wooden shingles, copper flashings

wooden shingles, double-lap tiling, 24 mm timber battens, 24 x 48 mm polyethylene (PE-HO) sheathing, 0.3 mm timber boards, 24 mm asphalt shingles, titanium-zinc flashings

asphalt shingles, 3 mm wood fibreboard, 24 mm

PEI primary energy renewable [MJ]

331

1 80

-

288

-

458

c:::J

1 55 c:::::J

1 43

GWP ODP global ozone warming depletion [kg C02 eq] [kg R 1 1 eq]

AP acidification [kg S02 eq]

EP eutrophication [kg PO.eq]

POCP Durability summer smog [kg C2H. eq] [a]

11

0. 1 0

0.0053

0.0 1 2

0

=

0

0.00001 2

0.10

0.0061

0.01 2

0

0

c:::::J

0

0.0000 1 5

0. 1 6

0.0086

0.0 1 3

0

0

C=:::J

0

0.0 1 2

0.024

=

4

D

17

c::::::J

830

1 30

35

=

689

1 97

0

0.000033

26

0

=

999

1 38

24

0.000087

=

501

910

708

1 15

flexible bitumen sheeting , with gravel

gravel, 50 mm polyester fleece (PES), 2 mm flexible bitumen sheeting (PYE PY200 S5), 5 mm flexible bitumen sheeting (G200 S4), 4 mm PVC, with gravel

gravel, 50 mm flexible PVC sheeting, 2.4 mm perforated glass fleece, 3 mm polyethylene (PE-HO) vapour barrier, 0.4 mm EPDM with gravel

gravel, 50 mm flexible EPOM sheeting, 1 .2 mm perforated glass fleece, 3 mm polyethylene (PE-HO) vapour barrier, 0.4 mm PVC with extensive planting

mm

1 355

38

58

-44

848

28

69 0

0.21

0

0.65

22

40

0.0 1 4

0.028

c::==::::J

c:::::J

0.014

0.058

c::==::::J

c====J

0.50

0.01 0

0.026

D

c::::J

c::==:J

=

0.000086

0.33

0.013

0.057

c===J

c====J

0.0 1 9

0.091

, =

0

0.50 c::::J

27

0

17

=

46

0

0

50

70 80 40

70

40

25

25-30

1 1

0.20

0.0 1 4

0.022

0

c::==::::J

Cl

0. 1 3

0.0086

0.028

0

C=:::J

c:::::J

0.54

0.0 1 9

0.054

=

50

=

0.0000 1 9

0

394

, c====J

j c===J

0

394

.16

c:::J

Cl

Roof waterproofing systems

plant-bearing layer, 80 mm polyethylene (PE-HO) filter fleece, 0.1 expanded clay filter layer, 30 mm drainage mats, extruded polystyrene root barrier, polyester fleece, 1 .5 mm waterproofing, flexible PVC sheetin g , perforated glass fleece, 3 mm polyethylene (PE-HO) vapour barrier,

PEI primary energy non-renewable [MJ]

25-30

25-35

30-40

I c==:::J

(XPS), 30 mm

2.4 mm 0.4 mm

C 1 .62

131

Insulating and sealing

Since the dawn of industrialisation in the 1 8th century, the concentration of carbon dioxide in the atmosphere has increased by more than 30% and has probably never been higher in the past 20 million years. Beside emissions from intensive agriculture (methane and d i nitrogen oxide) , it is mainly the carbon d ioxide released into the atmosphere by burning fossil fuels that contributes to the greenhouse effect and hence to g lobal warming. I n Germany more than one-third of the energy consumed annually is used for heating build­ ings. Thermal i nsulating and sealing materials significantly reduce the heating requirements of both old and new buildings. Modern standards of thermal insulation save more energy than is req u i red for the production and transport of the i nsulating materials - at the latest after two heating periods. Cavities of stationary air behind timber planking and the double-leaf masonry that began to appear at the start of the 20th century are regarded as the first con­ structional measures aimed at i mproving ther­ mal insulation and moisture control. I nsulating materials made from wood-wool, cork and min­ eral fibres first became available during the 1 920s. However, until the 1 970s the primary task of passive thermal insu lation was to avoid damage to the building and g uarantee hygienic living conditions. Energy economy

C 2.1 C 2.2

C 2.3 C 2.4

132

Infrared image of buildings Systematic classification of insulating materials according to their raw materials Comfort zone depending on U-value of wall with an external temperature of - 1 0°C Thickness of insulation required to achieve a ther­ mal resistance of 0.3 W/m2K

As a result of the oil crisis, the rapid increase in the price of crude o i l and the associated reali­ sation that our consumption of energy must be red uced, Germany passed its first Thermal I nsulation Act in 1 977, which was updated in 1 982 and 1 994. The prime aim of the act was to specify maximum thermal transmittance values (U-values) in order to reduce the transmission heat losses through external building compo­ nents, and hence lower the heating req u i re­ ments. The Energy Economy Act in force since 2002 instructs users to consider the influence of the airtightness of the building as wel l by determining the ventilation heat losses. The airtightness of building envelopes with good thermal insulation has a decisive effect on the heating energy requirements (see p. 1 42 ) . I nsulation and airtightness concepts

C 2.1

must therefore be coordinated at an early stage as part of a hol istic approach to the desig n .

Insulation principles

The insulating effect of a material improves as the air pores in the material become smaller, more numerous and more evenly distributed; stationary air in the pores is always a poorer conductor of heat than the surround ing solid material. Accord i n g to D I N 4 1 08, building materials with a thermal conductivity A < 0 . 1 W/mK can be classed as thermal insulating materials (fig . C 2.4). Owing to the g rowing demand for insulating materials and the increasing requirements to be met by thermal insulation, the number of dif­ ferent insulating products on the market is con­ stantly ris i n g . Mineral-fibre insulating materials and expanded foam materials are the most popular, with a combined market share exceeding 90%. In recent years insulating materials made from renewable raw materials have been red iscovered, and their application options are g rowin g . I nnovative i nsulating materials s u c h a s vacuum insulation panels (VIP) or infrared absorber­ modified polystyrene insulating materials (see "The development of innovative materials", p . 29) achieve considerably better insulation values (fig . C. 2 . 7 ) . T h e building materials industry c a n supply numerous products for the thermal insulation of external wal l s that are both loadbearing and insulatin g , e . g . l i ghtweight vertically perforated clay bricks. But the i nsulating function does reduce the load bearing capacity of the materi­ al. These products are dealt with in "Ceramic materials" (see pp. 50-5 1 ) . Classification

I nsulating materials are d istinguished accord­ i n g to the raw materials on which they are based (fi g . C 2.2): • •

inorganic, m ineral insulating materials organic insulating materials

Both organic and inorganic insulating materials

Insulating and sealing

Insulating material Inorganic, mineral made from natural materials

Organic

made from synthetic materials

made from natural materials

expanded clay

frothed glass

cotton

natural pumice

ceramic insulating foam

granulated cereals

expanded perlite

foam made from kaolin or perlite vermiculite

calcium silicate

made from synthetic materials urea-formaldehyde resin in situ foam (UF)

flax

mineral wool (MW) made from glass wool or rock wool

expanded melamine resin foam

expanded phenolic resin foam (PF)

hemp

polyester fibres

wood shavings

cellular glass (CG)

expanded polystyrene foam (EPS)

wood fibres (WF)

vacuum insulation panel (VIP))

extruded polystyrene foam (XPS)

wood-wool slabs (WW)

expanded polyurethane foam (PUR)

coconut fibres

polyurethane in situ foam (PUR)

cork products sheep's wool

bulrushes

straw/straw lightweight loam peat

cellulose fibres

can be made from natural or synthetic raw materials. We disti n guish between the following types according to their structure: • · ·

fibre insulating materials foamed insulating materials granulateslloose fill

• •

Functions and requirements

Thermal insulation • ·

•

Once the building is complete, the insulating materials are normally "invisi ble" . They fulfil a number of tasks and functions:

·

the temperature of the interior air can be con­ siderably lower but still achieve the same level of comfort. If the temperature of the interior air is lower, then the transmission and ventilation heat loss­ es are also lower. Reducing the temperature of the i nterior air by 1 K achieves savings in heat­ ing req u i rements amounting to approx. 6%.

Besides clothing and physical activities, there are other variables that are significant for human beings' perception of comfort i n enclosed rooms. These are:

·

·

sound insulation (depending on material) protecti n g the construction against conden­ sation or frost

Thermal comfort

Fibre materials form a type of no-fines material and hence prevent airflows. In foamed materi­ als the fixed cell structure and the enclosed air, or special gases, prevent convection.

•

C 2.2

guaranteeing a comfortable and hygienic interior climate reducing the transmission and ventilation heat losses preventing overheating in summer

air movements humid ity of the interior air temperature of the interior air and fluctuations thereof mean internal surface temperature

The temperature-related comfort zone regard­ ed as agreeable for the majority of people has been d etermined through comprehensive stud­ ies (fig . C 2.3). The temperature of the interior air and the mean internal surface temperature both contribute to chilling and hence the per­ ception of comfort to roughly the same extent. In buildings with good thermal insulation, the higher i nternal surface temperatures mean that 30

-11 - --

-

��

ta

=

- 1 0°C C 2.3

�

!

! j'" ! al al � K K � .n .n

Thermal conductivity The outward flow of heat takes place by way of conduction, radiation and convection. As a building performance parameter, thermal con-

11

u

20 -

The quality of the thermal insulation is based on the thermal properties and dimensions of the building materials and components used. Dur­ ing periods of cold weather there i s a constant flow of heat from inside to outside via the build­ i n g envelope. The term "insulation" describes the principal function of thermal insulating materials - to reduce the heat flow through the building com­ ponent layers.

-

0

'"

o O-n-

o

U -

0

0 -

0 �o

0

-

'"

r---

-

0

1l

&1 iD

IIf. 133

Insulating and sealing

C 2.5

C 2.6

Applications for thermal insulation to D I N V 4 1 08-1 0, table 1 Differentiation of certain product properties to DIN V 4 1 08-1 0, table 2

Part of building

Abbreviation

Typical applications

Floor, roof

DAD DAA DUK DZ

External insulation to floor or roof, protected from the weather, insulation beneath covering External insulation to floor or roof, protected from the weather, insulation beneath waterproofing External insulation to roof, exposed to the weather (upside-down roof) Insulation between rafters, double-skin roof, uppermost floor not designed for foot traffic but accessible Internal insulation to floor (soffit) or roof, insulation below rafterslloadbearing construction, suspended ceiling, etc. Internal insulation to floor or ground slab (top) beneath screed, without sound insulation requirements Internal insulation to floor or ground slab (top) beneath screed, with sound insulation requirements

01

Wall

Perimeter

DEO DES

WAS WAA WAP WZ WH WI WTH WTR

External insulation to wall behind cladding External insulation to wall behind waterproofing External insulation to wall beneath render I nsulation to double-leaf wall, cavity insulation I nsulation to timber-frame and timber-panel construction I nternal insulation to wall I nsulation between party walls with sound insulation requirements Insulation to partitions

PW PS

External thermal insulation to walls in contact with the soil (outside the waterproofing) External thermal insulation beneath ground slab in contact with the soil (outside the waterproofing)

ductivity 'A [W/mKj groups these three heat transport mechan isms together. It should be remembered that the lower the thermal con­ ductivity, the better is the thermal insulating effect of a material. The properties of metals make them especially conductive, with values up to 400 W/mK. Vacuum inSUlation panels achieve values as low as 0.004-0.008 W/mK by employing the thermos flask principle (vacuum layer) . The classification of thermal insulating mate­ rials into thermal conductivity groups ( e . g . WLG 035 or WLG 040) valid hitherto h a s been superseded since the introduction of the Euro­ pean product standards. According to D I N 4 1 08-4 the designation uses the so-called design thermal conductivity value, which can be specified in 1 mW steps ( e . g . 'A 0.028 W/mK) . =

a comfortable i nternal climate even in the case of high external temperatures. Building materi­ als that store heat help to even out the weather­ and uti l isation-related temperature fluctuations over the day. The specific heat capacity c specifies the storage capacity of a building material. Owing to their low weight, most i nsu­ lating materials have only a low heat storage capacity. Heavy insulating materials such as wood fibre insulating boards (density > 1 00 kg / m3) can be used in areas where overheat­ ing is likely ( e . g . converted roof spaces) in order to improve the thermal insulation in sum­ mer through their high storage capacity. Moisture control

There is a strong correlation between thermal i nsulation and moisture contro l . At 1 5°C water 'A 0.598 W/mK has a thermal conductivity 25 times greater than that of air ('A 0.024 W/mK) . Consequently, any water in a building material significantly reduces its thermal insulation capacity. Furthermore, moisture in building components can lead to corrosion, mould g rowth and frost damage. I n organic i nsulating materials water contributes to decomposition and destruction of the materials. In winter in particular, there is a vapour pressure grad ient between a heated interior and the cold outside air. The diffusion of water vapour from inside to outside can lead to condensation within exter­ nal wal l and roof constructions (interstitial con­ densation) . Insulating materials used in the cavities of double-leaf walls must therefore be hydrophobic (water-repellent) over their entire thickness. =

=

Thermal transmittance value (U-value) The U-value is the building performance parameter indicating the thermal transmittance of building components and i s specified in W/m2K. The thermal insulating properties of different constructions can therefore be com­ pared directly. A low U-value signifies a low heat flow through the building components and hence lower heat losses (U unit of heat trans­ fer) . Wherever components with a good thermal conductivity (e.g. concrete balcony slabs with­ out a thermal break) penetrate the insulated external wal l , the material properties lead to thermal bridges. Besides i ncreased heat loss­ es, there is also the risk of mould growth caused by the condensation that can col lect at such places. =

Specific heat capacity D I N 41 08-2 contains recommendations for ther­ mal insulation in summer in order to g uarantee

134

Water vapour diffusion The �-value specifies the d iffusion resistance of a material and has no units. Accordi n g to D I N 4 1 08-4 i nsulating materials made from mineral wool (� 1 ) , for example, are very =

C 2 .5

open to d iffusion, but cellular glass on the other hand is practically vapourtight (� 1 00 000). When designing external components, the dif­ fusion resistance of the individual component layers should decrease from inside to outside. The quantity of water diffusing into and out of the i nsulating materials, and hence possible risks to the materials, can be checked using the Glaser method ( D I N 41 08-3 ) . =

Sound insulation

In building work we d i stinguish between insu­ lating materials for airborne and structure­ borne (impact) sound when discussing their acoustic insulation properties. In order to improve the airborne sound insula­ tion of lightwei g ht walls or voids, soft fibrous insulating materials with a high flow resistance are particularly suitable. Such materials reduce the sound energy (air pressure fluctuations) as it passes through the fibres by converting into kinetic energy. I nsulating materials for impact sound insulation ( e . g . beneath floating screeds) are always elas­ tic and must exhibit minimal dynamic stiffness in order to absorb the incident i mpact energy and transfer only a part of this energy to the underlyin g structure. Fire protection

Insulating materials are also suitable for use in preventive, passive fire protection concepts in order to protect building components against rapid temperature rises. The majority of inorganic insulating materials belong to building materials class A ( incom­ bustible), but organic insulating materials only class B (combustible) . Health and environmental issues

Even though insulating materials are not gener­ ally in direct contact with the interior air, the

I nsulating and sealing

Product property

Abbreviation

Description

Examples

Compressive strength

dk dg dm dh ds dx

No compressive strength Little compressive strength Moderate compressive strength High compressive strength Very high compressive strength Extremely high compressive strength

Insulation to voids, insulation between rafters Residential and office areas beneath screeds Roof not designed for foot traffic, with waterproofing Roofs for foot traffic, terraces Industrial floors, parking decks Heavily loaded industrial floors, parking decks

zk zg zh

No requirements regarding tensile strength Low tensile strength High tensile strength

Insulation to voids, insulation between rafters External insulation to wall behind cladding External insulation to wall under render, roof w. bonded waterproofing

tk

No requirements regarding deformation Dim. stability not affected by moisture and temp. Deforms under load and thermal stress

Water absorption

wk

wf

wd

Tensile strength Acoustic properties

sk sg sm sh

Deformation

tf

No requirements regarding water absorption Absorbs liquid water Absorbs liquid or diffusing wate

No requirements regarding acoustics Impact sound insulation, low compressibility Impact sound insulation, moderate compressibility Impact sound insulation, enhanced compressibility

amounts of hazardous substances they contain (e.g. formaldehyde, styrene, isocyanate, phenol; see "Hazardous substances", p. 268) should nevertheless be kept to a minimum. The discus­ sion surrounding the toxicity to humans of addi­ tives (flame retardants in organic insulating materials, pesticides in some organic insulating materials made from natural materials) is on­ going. These days, foamed plastics production mostly uses pentane (pure hydrocarbon) or carbon dioxide. The use of CFCs (chlorofluorocarbons) and partially halogenated HCFCs has been banned throughout Europe since 1 995 and 2002 respectively. As an alternative, some manufacturers use chloride-free HFCs, whose ban is currently a subject of debate. Owing to the proven health risks of asbestos fibres and dust in interiors, synthetic mineral fibres are also suspected of having a carcino­ genic potential. For this reason, in 1 995 the insulating materials industry switched the pro­ duction of mineral wool to non-inhalable fibre thicknesses (carcinogenicity index � 40) and reduced the bio-persistence of rock wool . Like with all other fibre insulating materials, it should ensured at the planning stage that no fibres can be released into the interior air.

All applications without acoustic requirements Floating screeds, party walls Floating screeds, party walls Floating screeds, party walls

Internal insulation External insulation to wall beneath render, roof with waterproofing Roof with waterproofing

ty ( e . g . dh high compressive strength) . Accord i n g to their method of supply and instal­ lation, we d istinguish between boards, mats, felt, packing woo l , loose fill and in situ foams. From the building performance point of view, thermal insulating materials should be attached to the cold side of the construction whenever possible. However, in order to reduce the transmission heat losses from old buildings with facades protected by preservation orders, internal insulation is often the only solution. This treatment lowers the temperature of the wal l construction o n the cold s i d e a n d considerably increases the risk of interstitial condensation. As a rule, internal insulation calls for an extremely carefully installed vapour barrier or vapour check on the inside (see p. 1 45 ) . More­ over, thermal bridges at the wall-floor junctions are practically unavoidable. An vapour d iffu­ sion analysis is essential when using internal i nsulation. =

When choosi n g a suitable insulating material, the constructional framework conditions, the technical rules and the respective requirements should be taken into account: ·

•

Applications

The harmonised insulating materials standards D I N EN 1 31 68 to 1 3 1 7 1 are pure product standards and specify properties and designa­ tions only. The applications for thermal i nsula­ tion (fig. C 2.5) and the differentiation of certain product properties (fig. C 2.6) are regulated at national level (in Germany D I N V 4 1 08- 1 0 ) . The type codes are in each case made up of the application (e.g. WAA external wall i nsulation behind waterproofing) plus the product proper-

Internal insulation for residential and office areas External insulation to external walls and roofs Perimeter insulation, upside-down roof

·

•

·

•

=

•

General requirements: d i mensions, density, properties (texture, edges, colour, etc. ) Strength: compressive strength or compres­ sive stress at 1 0% compaction, long-term compressive stress, tensile strength, adhe­ sive strength of foams Dimensional stability when subjected to the effects of heat and cold Thermal i nsulation: thermal conductivity, ther­ mal resistance, heat storage capacity Moisture control: water vapour permeab i l ity, hydrophobic properties, water absorption Sound insulation: dynamic stiffness, flow resistance Fire protection: building materials class,

· ·

•

C 2.6

upper service temperature limit Health and environmental issues Durability: ageing resistance, resistance to high humidity, thermal stabil ity, UV radiation resistance Economic factors

Fixing

We distinguish between the following types of fixing irrespective of the choice of insulating material: ·

•

•

loose: no permanent mechanical connection, e . g . tipped, packed, blown in, laid loose individual : permanent ind ividual or l i near fix­ ings, e . g . nailed, screw, dowelled, glued full bond : a connection over the entire area of the insu lating material, e . g . g lued (adhesive, bitumen) , bedded in mortar

Recycling

The type of fixing has a crucial i mpact on the later recyclability of an insulating material. Materials i nstalled loose can usually be very easily reused, but those installed with a full bond are impossible to reuse. The technical options for recycling the materi­ als have developed at a faster rate than their practical application. Normally, mineral insulat­ ing materials are still sent to landfill sites, organic insulating materials are incinerated .

Insulating materials

The technical parameters of insulating materi­ als shown in fig. C 2 . 7 represent guidelines; these should be compared with the actual product data provided by the manufacturer in each individual case. A selection of insulating materials is given below.

135

Insulating and seali n g

Insulating material

Vapour diffusion resistance index

[kg / m,,]

Design thermal conductivity value [W/mK]

Inorganic, made from synthetic materials calcium silicate glass wool/rock wool cellular glass (CG)

1 1 5 - 290 1 2 -250 1 00- 1 50

0.045 -0.070 0.035 -0.050 0.040-0.060

2/20 1 /2 virtually vapourtight

A1 -A2/to A1 A1 - 8 1 /to A1 A1 /A1

Inorganic, made from natural materials expanded perlite (EP8) expanded clay vermiculite

60-300 260-500 60- 1 80

0.050-0.065 0.090 - 0. 1 60 0.065-0.070

2/5 2 2/3

A1 - 82 / to A 1 A1 /A1 A1 /A1

Organic, made from synthetic materials polyester fibres expanded polystyrene foam (EPS) extruded polystyrene foam (XPS) expanded polyurethane foam (PUR)

1 5 -45 1 5 - 30 25-45 " 30

0.035-0.045 0.035-0.040 0.030-0.040 0.025 -0.035

20/ 1 00 80/250 30/ 1 00

8 1 -2/to 8 8 1 /t0 8 81 /to 8 81 - 2 /to 8

Organic, made from natural materials cotton flax granulated cereals hemp fibres wood fibre insulating board (WF) wood-wool slab (WW) wood-wool multi-ply board (WW-C) coconut fibres insulation cork board ( IC8) sheep's wool cellulose fibres

Density

�

[-]

20- 60 0.040-0.045 1 /2 25 1 /2 0,040-0,045 1 05 - 1 1 5 n.a. 0.050 0.040-0.045 20-70 1 /2 45-450 0.040-0.070 1 /5 360-570 0.065- 0.090 2/5 heavily dependent on lay-up of plies 50- 1 40 1 /2 0.045-0.050 80-500 0.040-0.055 5/ 1 0 1 /2 20 - 80 0.035 -0.040 30 - 1 00 0.035 -0.040 1 /2

"Innovative" insulating materials (organic/inorganic) IR absorber modified EPS 1 5-30 transparent thermal insulation vacuum insulation panel (VIP) 1 50-300

0.032 0.02 - 0 . 1 3 0.004- 0.008

20/ 1 00 virtually vapourtight virtually vapourtight

Building materials class 1

Standard

Product forms

D I N EN 1 3 1 62 D I N EN 1 3 1 67

board board, fleece, packing wool board, loose fill

DIN EN 1 3 1 69 DIN EN 1 4063

DIN EN 1 3 1 63 DIN EN 1 3 1 64 D I N EN 1 3 1 65

81 -82/to 8 81 -82/to 8 82/to D 82/to D 82/to D 81 /t0 8 8 1 -82/to 8 81 -82/to 8 81 -82/to 8 81 -82/to 8 81 -82/to 8

DIN DIN DIN DIN DIN

EN 1 3 1 71 EN 1 3 1 68 EN 1 3 1 68 1 8 1 65- 1 /-2 EN 1 3 1 70

DIN EN 1 3 1 63

81 /to 8 82/to D

board, loose fill loose fill loose fill

fleece board board board, in situ foam

mat, felt, pack. wool, blow-in prod. board, mat, felt, packing wool blow-in product, loose fill board board board board mat, felt, packing wool loose fill, board mat, felt, packing wool blow-in product, board

board panel panel

The building materials classes are given as a guide only; they must be compared with the actual product data. Insulating material with building authority approval. 3 The insulating material exploits the static insulating effect plus solar gains; the values given here include solar gains determined over one heating period in Germany. These figures can vary considerably depending on climate and the orientation of the insulation. 4 Insulating materials for transparent thermal insulation systems fall into building materials classes A 1 to 83 depending on the raw material. 1

2

C 2.7 Mineral wool (MW) made from glass wool or rock wool

In Germany mineral-fibre insulating materials account for about 60% of the market - the larg­ est share. In terms of raw materials and bond­ ing of the fibres, we d istinguish between glass wool and rock wool. Glass wool (fi g . C 2 . 8 a) normally consists of recycled glass (approx. 50% by mass), quartz sand, feldspar, sodium carbonate and lime­ stone. In addition there is 3-9% binder made from synthetic resins (usually phenol-formalde­ hyde) and approx. 1 % waterproofing agent based on a silicone or on mineral oil. Rock wool (fig . C 2.8 b) is mainly produced from natural stone (e. g . d iabase, basalt, dolo­ mite), but can also contain clay brick and baux­ ite constituents from production waste. The proportions of binder and waterproofing agent are somewhat lower than those of glass wool . Just 1 m3 of stone produces about 1 00 m 3 of rock wool . The production involves melting the raw materials and additives at 1 300-1 500°C, which produces a pulp to which the b inder is added. M ineral-fibre insulating materials have equally good thermal and sound i nsulation properties. They are open to diffusion and are regarded as highly durable thanks to their rotting and

136

weathering resistance. However, insulating boards must be protected against extreme moisture because otherwise their insulating effect and strength are substantially reduced.

lular glass is normally bonded to components with bitumen, recycling is virtually impossible. Applications peripheral basement insulation and insulation beneath load bearing ground slabs thermal insulation to surfaces with heavy com­ pressive loads ( e . g . industrial floors, parking decks) internal insulation cavity i nsulation flat and green roofs •

Applications . Thermal insulation, airborne and i mpact sound insulation, and fire protection in virtual­ ly all situations

•

·

Cellular glass (CG)

Also known as foam glass, this material (fig . C 2 . 8 c ) is produced l i ke normal glass b y heat­ ing the raw materials quartz sand, feldspar, calcium carbonate and sod ium carbonate at about 1 400°C. The proportion of recycled g lass may account for about one-third of the total mass of raw materials. After cooling, the g lass is m il led to form a powder and carbon is added as a blowing agent (hence the dark grey col­ our) before the powder is heated again. The oxidation of the carbon causes the formation of gas bubbles which foam up the fluid mixture. Owin g to its closed-cel l structure impervious to gas, cellular glass is practically vapourtight, completely unaffected by water and d imension­ ally stable. It is therefore mainly used for build­ ing components in contact with the ground or those subjected to compressive loads. As cel-

• •

Calcium silicate insulating boards

Calcium silicate insulating boards have only recently been launched on the market (also with the designation mineral foam), and provide an alternative to the conventional insulating materials in thermal insulation composite sys­ tems. The raw materials are quartz sand, hydrated lime, cement and a curing agent with hydro­ phobic properties; about 1 0% cellulose is added to boards for internal use. They are pro­ duced (formation of pores, hardening and dry­ ing) in autoclaves like aerated concrete. Calci­ um silicate insulating boards are very open to diffusion and thanks to their water absorption ability contribute to regulating the humidity of

Insulating and sealing

the interior air, which makes them suitable for use as internal insulation on external walls, When used external ly, the water absorption is reduced to s;; 5% by adding a waterproofing agent. If this insulating material is incorporated in a mineral wall construction, the complete wall can be disposed of as a whole, Owing to the higher density of calcium s i licate insulating boards, they seem clearly more massive than conventional thermal insulation composite sys­ tems, Applications external and internal insulation to walls fire protection •

•

Expanded perlite

Perlite (fig , C 2 , 8 d) is among the group of aqueous, vitreous rocks with a volcanic ori g i n , In the expanding process crushed raw perlite is briefly heated to about 1 000°C to g ive it a viscous consistency, The water in the rock turns to steam and expands the particles to max, 20 times their original volume, A silicone waterproofing agent or encasing in bitumen or a natural resin can be used depending on the intended use of the material, Loose fi l l perl ite treated with waterproofing agent is open to d if­ fusion, hardly affected by moisture and cannot rot. Expanded perlite is either combustible or incombustible depending on the encasing material. Expanded perlite boards (EPB) can be pro­ duced by addi n g binders plus organic and inorganic fibres, Applications lightweight aggregate for concrete and mortar cavity insulation thermal and impact sound insulation levelling layer beneath screeds loose insulation for roofs and timber joists floors •

·

·

•

•

Expanded clay

After the clay is obtained from open-cast m ines it is stored for about a year, The processing involves milling the raw material and passing it through a rotary kiln where it is dried using the countercurrent method and subsequently heat­ ed to approx, 1 200°C, at which temperature the bonded water turns to steam and expands the particles, Expanded clay does not rot and can withstand high compressive loads, However, the thermal insulation characteristics (approx, 0,09 W/mK) are rather poor when compared to other insu­ lating materials, Applications lightweight aggregate for concrete and mortar levelling layer beneath screeds thermal insulation in floors

Expanded polystyrene foam

Polystyrene (fig , C 2 , 8 e) has been used by the building industry since the 1 950s and in Ger­ many has the second-largest share of the mar­ ket. In the production of EPS, polymerisation creates EPS beads (0, 1 -2,0 mm) from the raw material styrene (obtained from petroleum or natural gas) by adding a highly volatile blowin g agent (pentane) , After drying a n d intermediate storage, the granulate is heated with steam i n pre-foam i n g units a t temperatures of approx, 1 00°C, which causes it to expand to 20-50 times its orig i nal volume before being formed i nto boards on a continuous production line, The proportion of pure recycled EPS can amount to 40% dependi n g on the application, Expanded polystyrene foam does not rot. but becomes brittle in direct sunlight (no resistance to ultraviolet radiation) and is not resistant to solvents, Owing to its comparatively high vapour d iffusion resistance, when used as i nternal i nsulation it should be ensured at the planning stage that any condensation can evaporate again, However, EPS products open to d iffusion are also available, Owing to its sen­ sitivity to temperature (max, temperature in use: 75-85°C) , this material cannot be bonded with hot bitumen or used beneath mastic asphalt. Applications thermal insulation i n almost all situations i mpact sound insulation • •

Extruded polystyrene foam (XPS)

The chemical composition of extruded polysty­ rene foam (fig , C 2 , 8 f) is almost identical to that of expanded polystyrene foam, Polystyrene granulate is melted in an extruder, foamed up by adding a blowing agent and formed into a continuous web of foam material. The blowing agent used is normally carbon dioxide these days, i nstead of the CFCs or HCFCs employed in the past. After production, all the carbon d ioxide escapes from the materi­ al and is replaced by air, XPS absorbs very little water and has a high compressive strength, It has a high diffusion resistance, but is not resistant to u ltraviolet radiation and cannot resist solvents, The maxi­ mum temperature for applications is 75°C, Applications peri pheral basement i nsulation and insulation beneath load bearing ground slabs thermal insulation to surfaces with heavy compressive loads (e,g, industrial floors, parking decks) upside-down roofs i nsulation to thermal bridges (concrete l i ntels, i nsulated starter-bar units) ·

·

·

·

•

Polyurethane foam (PUR)

•

Polyurethane foam (fig , C 2 , 8 g) achieves the best insulation values among conventional insulating material s , Its main constituents are d i phenylmethane di-isocyanate ( M D I ) , poly­ ether and/or polyester polyalcohol ; the latter

•

g C 2,7 C 2,8

C 2,8 Physical parameters of selected insul. materials Insulating materials (selection) a Glass wool b Rock wool c Cellular glass d Expanded perlite e Expanded polystyrene foam f Extruded polystyrene foam g Expanded polyurethane foam

137

I nsulating and sealing

can be produced from crude oil or renewable raw materials (e. g . sugar beet, maize, pota­ toes). Polyurethane foam is produced by mix­ ing and the chemical reactions between the l iq­ uid components when a blowin g agent such as pentane or carbon d ioxide is added. Depending on the method of production, it i s possible t o produce insulating boards without facings (slabstock foam boards), or with flexible (laminated foam boards) or rigid facings (sand­ wich panels) . Polyurethane boards laminated with aluminium on one side are vapourtight and achieve (dependi n g on product) 1--- values of 0.025 W/mK. I n situ polyurethane foam is also available in add ition to the boards. The in situ foam i s made from simi lar raw materials and is used to fi l l voids on site. Polyurethane i s not resistant to ultraviolet radia­ tion, but does not rot and, unli ke polystyrene, is resistant to both hot bitumen and solvents.

a

b

Applications insu lation over the rafters flat roofs thermal insulation to surfaces with heavy compressive loads (e. g . industrial floors, parking decks) thermal insulation beneath floating screeds sandwich panels filling of voids (in situ foam) •

•

•

c

Wood fibre insulating boards (WF)

The raw materials for the manufacture of wood fibre insulating boards (fig . C 2 . 9 b) are low­ strength wood (e.g. spruce, fir and Scots p ine) or scrap wood from sawmills. The chips are crushed, mixed with water to form a p u l p , dried to 2% residual moisture con­ tent and cut into boards. The bond is generally based on the interlocking of the fibres and the adhesive q ualities of the l i g n i n already present in the wood. Some manufacturers add small amounts of aluminium sulphate, paraffin or glue to assist the bonding process. We essentially d istinguish between porous and bitumen ised wood fibre insulating boards - the bitumen improves the moisture resistance. Wood fibre insulating boards absorb moisture, are relatively open to d iffusion, are airtight and have a high heat storage capacity. They can be recycled , and the boards without bitumen can also be composted. Applications insulation over and between rafters, also to contain loose insulating materials thermal insulation to wal l s and floors impact sound insulation •

·

·

•

•

Cork products

•

Cork insulating materials are made from the bark of the cork oak, mainly indigenous to Por­ tugal, Spain and Algeria. The first stripping is when the tree is 25-30 years old, and subse­ q uent bark removal can take place every 1 0 years without endangering the tree. Supplies of cork are therefore not unlimited and the whole process is relatively costly. We d i stinguish between various cork products depending on the method of manufacture. I n the production of insulation cork board (ICB) the bark is m i l led to form a granulate and baked under pressure in hot steam (approx. 370°C). The cork expands by 20-30% of its original volume and the resin that is released b i nds the granules into blocks (fig . C 2 . 9 c ) . Pressed cork board is produced by compact­ i n g the milled cork granulate into blocks under high pressure and subsequently sawing the blocks to form boards. I mpregnated cork con­ tains additional binder (e.g. bitumen). Granulat­ ed cork is obtained through the mechanical milling of the bark without any further additions. All cork products have relatively good thermal insulation properties and also a high heat stor­ age capacity.

Wood-wool slabs ('NW)

These consist of long wood shavings (mostly spruce). The fibres are mixed with mineral binders (magnesite or cement) , pressed together at high temperatures and subsequent­ ly dried. The chips can be pretreated with mag­ nesium sulphate to protect against insect attack. Cement-bonded boards (grey colour) absorb more water than magnesite-bonded boards (beige colour) . Wood-wool slabs have a good heat storage capacity, are open to d iffusion and can contrib­ ute to sound attenuation.

d

e

Applications permanent formwork internal fitting-out, sound-attenuating lining plaster background · ·

•

Wood-wool multi-ply boards (WW-C)

C 2.9

g C 2.9

138

Insulating materials (selection) a Wood-wool multi-ply board b Wood fibre insulating board c Insulation cork board d Cotton e Cellulose fibres f IR absorber-modified polystyrene g Vacuum insulation panel

These boards (fi g . C 2 . 9 a) consist of a core of expanded foam or mineral-fibre i nsulation and a facing of m i neral-bonded wood-wool on one side (2-ply board) or both sides (3-ply board) . The properties are the result of the respective build-up of wood-wool and i nsulation (e.g. min­ eral fibre, EPS, PUR). I n contrast to normal wood-wool slabs, wood-wool multi-ply boards comply with modern insulation standards. Applications permanent formwork insulation to the underside of roofs over base­ ments or basement parking insulation to thermal bridges (e.g. edges of floor slabs) •

Applications thermal and impact sound insulation below floating screeds or wood floor finishes insulation to l i ghtweight partitions and timber joist floors granulated cork as a loose insulating material (attenuation to voids, roofs) ·

•

•

•

•

Sheep's wool

This product comes mainly from Central Europe, but supplies from overseas (e.g . New Zealand)

Insulating a n d sealing

are also on the market. The raw wool contains about 40% grease (yolk) , foreign matter and perspiration that is removed i n the washing plant with soap and soda. Some manufacturers enhance moth protection by adding 1 -2 % by mass additions of boron salt in the order of magnitude of 1 % by mass serve as a fire retardant. After carding (disentangling and straightening) the wool, it is processed to form a thin fleece, several layers of which are nee­ dled together to form insulating mats. Fine wool - a waste product of the production process can be used for packing purposes or as back­ ing cords for joints. Sheep's wool is open to d iffusion and very hygroscopic - the fibres can absorb moisture (up to 33% by mass) and release it again with­ out impairing their insulating effect. Applications thermal insulation to (close) couple roofs insulation to l i ghtweight partitions and timber joist floors impact sound insulation packing and attenuation in voids •

·

·

·

Cotton

Cotton insulation board (fig . C 2.9 d) is pro­ duced from roughly equal parts of raw cotton and offcuts and scraps from the textiles indus­ try. Raw cotton consists of 90% cellulose, wax and pectin. The production involves cardi n g the raw mate­ rial, cleaning it mechanically and adding boron salts (pesticide, fire protection ) . Afterwards, it is processed to form a thin fleece, several layers of which are needled together to form insulat­ ing mats. This building material exhibits very good thermal and sound insulation properties. The debate continues about whether cotton - a renewable raw material - is also worthwhi l e as an insulating material from the economic view­ point. In a life cycle assessment the relatively low energy requirements of the production are offset by the long transport d istances, and the environmental effects of fertilisers and pesti­ cides are not taken into account. Some manu­ facturers use hand-picked cotton , which usual­ ly requires no pesticide, as their basic raw material .

tection) , several layers of the fleece are bond­ ed together with potato starch or by weaving in reinforci n g polyester fibres. Flax insulating materials are open to d iffusion and exhibit very good thermal and sound insulation characteris­ tics. Applications thermal insulation to floors and roofs impact sound insulation packing ·

•

•

Cellulose fibres

Among the insulating materials made from renewable raw materials, cellulose fibre prod­ ucts currently enjoy the largest market share. The raw material is scrap paper, e . g . daily newspapers printed with lead-free printing i nk, and other waste paper products. Flakes (fi g . C 2.g e) and boards made from cel­ lulose fibres d iffer with respect to methods of production and applications. In the production of cellulose flakes the scrap paper is crushed in a m ulti-stage process and mixed mechanically with boron salt (20% by mass) to improve the fire protection properties. In the production of cellulose fibreboards, rei n­ forcing fibres (jute or polyolefins) and binders (lignin sulphonate) are added after pulverising the scrap paper and mixing in the boron salt. Aluminium sulphate and tal l oil are used as waterproofing agents. Cellulose fibres exhibit very good thermal i nsu­ lation properties, are hygroscopic and open to d iffusion. The material is durable and has been used in Scandinavia and the USA since the 1 920s. However, only the processing by trained operatives in approved specialist plants guarantees non-settli n g products free from voids. For recyc l i n g , the flakes are easily col­ lected by vacuuming . Applications thermal i nsulation to (close) couple roofs and timber joist floors i nsulation to l i ghtwei g ht partitions attenuation in void s •

•

·

Innovative insulating materials

The ever more stringent thermal insulation standards and the i ncreasing thicknesses called for are currently encourag ing rapid developments and trials of highly efficient i nsu­ lating materials. Based on industrial research and development programmes, the efficiency of existing materi­ als can be constantly improved through the use of novel combinations and new effects (see "The development of innovative materials, p. 28). For examp le, adding an infrared absorber to the matrix of expanded polystyrene (fi g . C 2.9f) renders possible a reduction in thickness of up to 25% (see fig. C 2.4, p . 1 33) . The (still) comparatively high cost of such inno­ vative insulati n g materials must be weighed against the considerable gain in usable floor space and the new design options (more slender components) . For refurbishment work, high-performance insulating materials result in modern U-values even with thin assemblies ( e . g . adjacent neighbouring structures, junc­ tions around windows, short eaves overhang) . Vacuum insulation panels (VIP)

Vacuum i nsulation panels (fi g . C 2 . 9 g ) have been establ ished for use in refrigerators and deep freezes since the 1 970s, but it is only recently that the first trials and demonstrations for b u i l d i n g applications have been carried out successfully. I n comparison with conventional insulating materials, the thermal conductivity is lower by a factor of 5-1 0 . VIPs consist of a core material with a good compressive strength that is lami­ nated with gastight composite foils in a vacuum chamber. Besides fibres and open-cell foams, pyrogenic silicic acid is now the favourite filling material because - owing to its extremely small voids ( 1 00 nm) - thi s places the lowest demands on the airtightness of the envelope. The initial gas pressure is 1 -5 mbar and increases by approx. 2 mbar every year. The airtightness has a decisive influence on the durability and thermal conductivity of VIPs: · · ·

Applications thermal insulation to (close) couple roofs insulation to lightweight partitions and timber joist floors packing and attenuation in voids •

•

0.004 W/mK at < 5 mbar gas pressure 0.008 W/mK at < 1 00 mbar gas pressure 0.020 W/mK ventilated

The use of aluminium foi l or multi-layer, vacu­ um-metall ised synthetic barrier foils results in a guaranteed l ifetime of 30-50 years.

•

Flax

In Central Europe flax plants g row to a height of approx. 1 .0-1 .2 m, have a relatively short vege­ tation period and do not usually require any fer­ tilisers or pesticides. The short fibres used for flax insulating materials are a by-product of the process to obtain long fibres for the textiles industry (linen). The retted (soaked) and dried short fibres are carded and processed to form a thin fleece. After adding boron salts (fire pro-

Applications thermal insulation beneath underfloor heating internal i nsulation with faci n g of plasterboard spandrel elements for post-and-rail facades thermal insulation composite system in con­ junction with 35 mm XPS boards as plaster background (protective layer) ·

· ·

·

139

I nsulating and sealing

�

� o U)

o N

1W��,RJU Il-- 1

�

- ---

2

--

11?11I11--- 3

--

:oIIIHr--- 4

-� -� -

�

----

::ifI11r--- 5

--

-

---

6

--

.>Il/llIlr-- 7

--

1 2 --, 3

-� �

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---

1 2 3 4 5 6

7

Solid timber, spruce, 80 mm Softboard, 22 mm Vacuum insulation panel, 40 mm Compressible tape all round Battens, 40 x 45 mm Softboard 3-ply core plywood, 22 mm

C 2.10

Planning advice I n order to achieve U-values ,,;; 0. 1 5 W/m2K, i . e . passive-energy house standard, with conven­ tional insulating materials, a total wal l thickness > 500 mm is normal. In a pi lot project by Lichtblau Architekten, a U-value of 0. 1 4 W/m2K was achieved using a loadbearing sol id timber wal l and interchange­ able VIPs - with a total wall thickness of just 1 92 mm (fi g . C 2 . 1 0) . The thinner wal l results in a gain in usable floor space amounting to about 1 5 m2 (in relation to the total floor space of 265 m2) . The following aspects should be considered at the planning stage: •

•

•

·

Defined sizes (usually 1 .0 x 0.5 m): the panels cannot be cut, special sizes are time-consum­ ing and costly. Protection of the vacuum: the panels need a fixing without restraint, and the insulating layer must not be damaged ( e . g . nails) during construction and uti l isation of the build i n g . Thermal bridges: in comparison t o VIPs, air is a good conductor of heat; therefore joints and penetrations must be minimised . So far there is no building authority approval.

Transparent thermal insulation

Transparent thermal insulation enables the transmission heat losses through opaque exter­ nal walls to be reduced but the same time per­ mits high solar radiation transmission and, moreover, acts as a daylight element i n a trans­ lucent facade. The insulating material often makes use of cel­ lular structures (capillary, honeycomb) of glass or plastic (PM MA, PC) . Alternatively, honey­ comb structures made from recycled paper or microporous aerogel bead fillings are feasible. The insulating materials are protected against the weather, dust, dirt and mechanical damage by fitting them in the cavity of insulating glass units or between profiled glass elements or in multi-walled panels. How it works Generally, we d istinguish between three d iffer­ ent transparent thermal insulation systems:

1 40

1 2 3 4 5 6

•

•

·

-- Solar radiation

- -- Heat radiation

Glass Shading element Transparent thermal insulation Glass Absorber Masonry

---

�

a 1 2

C 2.1 1

D i rect gain system: In terms of their appearance, translucent ther­ mal insulation units integrated into post-and­ rail facades resemble acid-etched or sand­ blasted glazing (fi g . C 2 . 1 3) . The l i ght-scatter­ i n g effect of the thermal insulation structure distributes the daylight deep into the interior evenly and without g lare. In the form of triple g lazi n g with an 8 mm thick capillary panel, U-values of 0.8 W/m2K are possible. Solid wall system: The combination of transparent thermal insu­ lation elements and heat storage mass en­ ables the incident solar radiation to be con­ verted into heat at the (usual ly) b lack-painted outside face of the wal l (absorber) and trans­ ported to the i nside face of the wall after a delay (fi g . C 2 . 1 1 ) . Through the reversal of the heat flow during periods of incident solar radi­ ation, this construction realises gains of 501 50 KWh /m2 per square metre of transparent thermal insulation (depending on system, orientation, shad i n g , etc . ) . Thermally decoupled systems: Convective and hybrid systems are decoupled from the storage mass by controllable air or water layers. However, such systems are sti l l a t the development stage.

3

b Glass Panel in heating mode Masonry

1 2

3

Glass Panel in insulating mode Masonry

C 2. 1 2

converted into heat and transported to the interior via the solid masonry after a delay (fig . C 2 . 1 2) . I n insulating mode the element protects against heat losses and overheating in summer. Switching between the two modes is achieved by applying an electric current, which i nfluences the pressure relationships of the g lass-fibre core and hence alters the thermal conductivity by a factor of 40.

C 2 . 1 0 Solid timber external wall construction with inter­ changeable vacuum insulation panels C 2. 1 1 Transparent thermal insulation element with shading and temperature gradient C 2 . 1 2 Switchable thermal insulation a in heating mode (heating period and sunshine) b in insulating mode (all other times) C 2 . 1 3 "Rathausgalerien" shopping mall, Innsbruck, Austria, 2002, Dominique Perrault C 2 . 1 4 Life cycle assessment data for insulation and sealing

To protect against overheating in summer, transparent thermal insulation systems must be fitted with effective sunshades. Besi des electri­ cally driven foil roller blinds, cover plates attached manually (seasonally) are also used. Passive measures (e.g. eaves overhang , bal­ cony) can also provide some shade, but reduce the overall solar gains achievable. Switchable thermal insulation

Switchable thermal insulation is based on the knowledge gained from VIPs and transparent thermal insulation and to date only one pilot project has been completed. The facade ele­ ments can be switched as required from a highly insulating state with U-values of 0.20.3 W/m2K to a solar collector state with much higher thermal conductivity and a U-value of 1 0 W Im2K. On sunny but cold winter days (heating mode) the incident solar radiation is

C 2.13

I nsulating and sealing

Insulation Layers , for origin of data see "Life cycle assessments", p. 1 00

PEI primary energy non-renewable [MJ]

PEI primary energy renewable [MJ]

GWP global warming [kg C02 eq]

OOP ozone depletion [kg R1 1 eq]

AP acidification [kg S02eq]

EP eutrophication [kg PO. eq]

POCP summer smog [kg C2H . eq]

51 1

17

28

0

0.70

0.0062

0.022

Boards expanded polystyrene (EPS) EPS board, A = 0.040 W/mK, p = 25 kg/m3, 1 20 mm polyvinyl acetate adhesive (PVAC) extruded polystyrene (XPS)

c:::=:J 405

12

21

0

0.0049

0.50

XPS board, A = 0.040 W/mK, p = 20 kg/m3, 1 20 mm polyvinyl acetate adhesive (PVAC) polyurethane PUR

= 0.0 1 3

0.01 1

0.0060

0.00041

0.001 0

0

0.038

0.0036

0.0050

CJ

CJ

0

0. 1 3

0.0083

0.020

CJ

=

0.35

0.0 1 4

349

13

17

0

0. 1 8

15

0.24

1 .1

0

68

0.8

19

PUR board, A = 0.035 W/mK, p = 2 0 kg/m3, 1 00 mm polyvinyl acetate adhesive (PVAC) insulation cork board ICB'

0.01 6

CJ

c:=:=:J

ICB, A = 0.040 W/mK , 1 20 mm mortar-based adhesive wood-wool multi-ply board WW-C, permanent formwork'

89

V1/W-C board, A = 0.040 W/mK, p = 30 kg/m3, 1 25 mm magnesite-bonded, mineral fibres on inside

-

wood fibre insulating board WF'

436

WF board, A 0.040 W/mK, p mortar-based adhesive

1 60 k9/m3, 1 20 mm

cellular glass CG, perimeter insulation' cellular glass, A 0.040 W/mK, p bitumen compound

D

79 CJ

1 030

1 00 k9/m3, 1 20 mm

29

49

0

0

calcium silicate board

96

calcium silicate, A = 0.045 W/mK, p = 1 1 5 kg/m3, 1 40 mm mortar-based adhesive

-

3.7

c:=:=:J

16

0

c==:::::J

0.0 1 5 I

c==:::::J

0.061

0.0044

0.0030

0

c::::J

0

0.037

0.0038

0.0050

c::::J

=

0.0074

0.01 2

Fleeces mineral wool fleece

74

mineral wool lleece, )" = 0.040 W/mK, p = 20 kg/m3, 1 20 mm polyamide fixings

-

1 .4

5.4

0

=

Loose fill 2.1

perlite fill

1 87

expanded perlite, )" = 0.065 W/mK, p = 1 00 kg/m3, 1 60 m m (on ground slab)

-

cellulose fill

33

cellulose, )" = 0.040 W/mK, p = 50 kg/m3, 1 20 mm (between TJI timber beams)

•

Sealing Layers , for origin of data see "Life cycle assessments", p . 1 00

PEI primary energy non-renewable [MJ]

PEI primary energy renewable [MJ]

reaction resin waterproofing

94

3.4

epoxy mortar, 2 mm epoxy undercoat

-

plastic-modified thick bitumen coatin 9

373

11

0

0.20

I:::=J

c:==:=J

c:==::J

0

0.0 1 2

0.00074

0.0010

GWP global warming [kg C02 eq]

OOP ozone depletion [kg R 1 1 eqj

AP acidification [kg S02 eqj

EP eutrophication [kg PO. eqj

POCP summer smog [kg C2H, eqj

5.8

0

0.040

0.0029

0.0030

0

I:::=J

0

0.042

0.0044

0.0 1 5

0

c:::=:J

0

0.0030

0.00035

0

0

0.23

0.010

0.01 5

c::::::J 1 .7

1 .8 0

Spread compounds

= 1 .1

6.4

0

c==:::::J

embossed synthetic sheeting for protection (HDPE) bitumen emulsion, 3 mm mineral waterproofing

10

cement-based waterproofing, 2 mm water glass undercoat

•

0.2

0.8 0

Flexible sheeting PVC sheeting, 1 layer

31 2

PVC sheeting, 2 mm polyethylene fleece, 0.5 mm bitumen sheeting, 1 layer bitumen sheeting (G200 S4), 4 mm bitumen undercoat

35

20

=

294

5.6

I

7.4

0

I

0.091

0.0038

c::::::J

='

0.020

C 2. 1 4

1 41

I nsulating and sealing

C

Sealing

The sealing of joints or junctions between build­ ing components or their surfaces protects the building against the ingress of water, the un­ controlled loss of warm interior air through the building envelope and the ingress of cold air from the outside. Damaged or incomplete seal­ ing of joints and surfaces can lead to serious damage and increase the heating energy requirements significantly. Every b u i l ding includes a multitude of joints which compen­ sate for tolerances and enable the various components to move without restraint as they expand and contract in harmony with tempera­ ture fluctuations. In addition, joints can also be used as a means of adding texture or features to a surface, or to reflect geometrical or con­ structional configurations. Airtightness

Air can absorb water vapour up to the satura­ tion vapour pressure, i . e . until reaching the dew point, at which point the water condenses. Hot air can absorb more water vapour than cold air. As hot air cools, so its relative humidi­ ty rises. If the dew point i s reached, the water condenses within the building component (interstitial condensation). This promotes the growth of fungi (mould) , causes rotting of tim­ ber components and reduces the insulating effect of thermal insulation. Cold air that enters from outside via leaking joints can carry fibres, fungi and spores from the building compo­ nents into the interior air. These may l ead to health disorders among the occupants, gener­ ally summarised under the head i n g of "sick building syndrome". Interestingly, moisture damage to b u i l di n g components caused by condensation is mainly the result of airtig htness problems and convec­ tion, and less often water vapour d iffusion. Only approx. 1 % of the water vapour passes through the external wall as a result of the water vapour gradient between inside and out­ side. In this context it is worth noting that only proper ventilation - if necessary with controlled mechanical systems - guarantees the changes of air necessary to meet hygiene and energy economy requirements.

1 42

Blower door measurements Leaks in the b u i l d ing envelope can be estab­ lished and localised with the help of blower door measurements. In new buildings these measurements should be carried out before installing partitions and soffits, but after all win­ dows, doors, sealing layers and plastering works have been completed. One external door is temporarily removed and replaced by a special sealed fan unit which creates a (negative) pressure difference of 50 Pa between i nside and outside. Any leaks in the building envelope will cause air to be drawn into the building, which is then extracted with the fan. The measured airflow corresponds to the leakage flow (in m3/h) caused by leaks in the building envelope. Dividing this value by the vol ume of the building produces the air change rate . According to the Energy Econo­ my Act 2002, the air change rate shou ld not exceed 1 . 5/h for buildings with mechanical ventilation, and in passive-energy houses it may not exceed 0.6/h . If these values are exceeded, the leaks can be localised with special instruments. We distin­ guish between leaks in the external building components and leaks in joints around win­ dows and external doors. Leaks also impair the airborne sound insu lation. Even at the draft design stage it is important to ensure that the airtight layer is carefully planned, the aim being to provide surfaces and joints that are permanently airtight. I n doing so, it is primarily penetrations of the airtight layer, e . g . pipes and cables or loadbearing structure, that should be considered as potential weak­ nesses.

2. 1 7

Sealing of joints

Deformations of building components are caused by, for example, settlement, tempera­ ture-related changes in length or shrinkage. Poor workmanship may lead to crackin g . I n order t o keep such processes under control and to avoid damage, the effective lengths of components are limited by planned joints. I n terms of construction we distinguish between the following types of joint: Construction joints Construction joints are rigid joints. They are the result of the building process, e . g . between concrete components that cannot be poured in one operation. Construction joints always occur between foundation and walls, but the load of the walls and the continuous reinforcement is usually sufficient to seal such construction joints. However, shrinkage cracks often form at these points. A planned dummy joint simplifies the subsequent sealing of this crack because it provides space for a seal ing compound. Expansion joints Expansion joints permit the horizontal move­ ment of large building components. In order to avoid uncontrolled cracking in the structure, vertical expansion joints extend over the full height of the building, down as far as the top of the foundation, e . g . in reinforced concrete walls or a faci n g leaf of clay bricks. Expansion joints that are sealed with jointing materials to prevent ingress of rain and splash­ ing water are not waterproof in building tech­ nology terms. According to D I N 1 8 1 95 a water­ proof joint is achieved only with flexible water­ proof sheeting or a thick bitumen coatin g .

Watertightness

Planar waterproofing systems prevent the ingress of water i nto the b uild ing. Numerous materials are available for this, and these may also be combined. Besides their waterproofing characteristics, such materials should also be able to bridge over any cracks so that the sur­ face remains watertight even in the case of movement. Joint sealants complement the waterproofin g systems.

Settlement joints Different parts of the building with d ifferent total loads exert unequal vertical loads on the sub­ soil . In order to permit d ifferential settlement without restraint, settlement joints must also continue through the foundations. Separating joints Components with different physical properties, e . g . at junctions around windows, must be iso-

I nsulating and sealing

/

/

/

/

/

a

C 2. 1 8

b

lated b y separating joints that can accommo­ date temperature-related changes in length and dimensional tolerances. Such joints can also act as expansion or settlement joints at the same time. Maintenance joints These are joints exposed to severe chemical or physical influences. They must be readi l y accessible s o that they c a n be inspected regu­ larly and renewed as required. Joints without special requirements may be left open (drained joints). Other joints must be sealed . Various sealing materials can be used depending on type of joint and requirements. These materials can create any standard from draughtproof to watertight and are d ivided into the following groups: joint sealants (injectable, kneadable) waterstops sealing strips, seal i n g gaskets Joint sealants, sealing strips and sealing gas­ kets for press i n g , inserting and glueing i nto place are not suitable as the sole means of sealing i n the case of hydrostatic pressure.

b

C 2.19

Joint sealants that dry physically, e . g . butyl compounds, sol idify as the solvent or water evaporates. In the case of non-reactive joint sealants, the material does not alter after being installed. We d istinguish between plastic and elastic joint sealants depending on their defor­ mation characteristics. The permissible total deformation is max. 25%. Joint design Accord i n g to D I N 1 8 540 a joint consists of two sides, if possi ble with chamfered edges and a stable substrate. A round backing strip limits the depth of the joint and prevents the joint sealants adhering to three surfaces (fig . C 2 . 1 8) . In order to g uarantee the deforma­ bility of the joint, the backing material consists of a rot-resistant, closed-cell foam material. Only joints with a width-depth ratio of approx. 2 : 1 ( e . g . 20: 1 0 mm) wi l l remain sealed perma­ nently. The joint sealant should be pressed onto the sides of the joint to ensure adhesion. Sealants are injected from cartridges or pressed i nto place as a kneadable plastic compound. Expansion and construction joints in contact with the soil must satisfy more strin gent require­ ments, which are given in 01 N 1 8 1 95-8.

Injected joint sealants must be stable, must adhere well to the two sides of the joint (if nec­ essary in conjunction with a primer to enhance the adhesion), must withstand changing climat­ ic and mechanical loads (resi l i ence and expan­ sion behaviour), must exhi bit a non-sticky sur­ face and must be compati ble with the adjoining building materials. They should also be suitable for uneven joint surfaces. According to D I N 1 8 540 joint sealants should not be painted afterwards because the antici­ pated deformation of the sealant is usually greater than the elasticity of the paint. The out­ come is that the paint cracks and flakes off. Nevertheless, in practice sealants are often painted for aesthetic reasons.

Silicone sealants S i l i cone sealants undergo a chemically reactive curing process which exploits the moisture i n the a i r a n d produces an elastic seal . The prod­ ucts given off are acetic acid, amines or alco­ hols, depend i n g on the particular system. Sili­ cone sealants exhibit acid ic, neutral or alkal ine reactions and must be compati ble with the sub­ strate. Some products give off odours as they cure. Silicone sealants adhere very well to smooth, mineral substrates such as glass and ceram­ ics, also aluminium and coatings, both i nternal­ ly and externally. Sanitary applications, junc­ tions, terraces and balconies are the main uses. They are available in many different col­ ours.

Chemically reactive joint sealants, e . g . silicone sealants, cure due to the effects of the moisture in the air and expel molecules.

Polyurethane sealants Polyurethane sealants also undergo a chemi­ cally reactive curing process and g ive off car-

Joint sealants

C 2 . 1 5 Separating joints between precast concrete ele­ ments, office building, Munich, Germany, 2003, Amann & Gittel C 2 . 1 6 Expansion joint, separating joint C 2 . 1 7 Material and room transitions marked by joints, Museum of Modern Art, Kanazawa, Japan, 2005, Sejima Nishizawa C 2 . 1 8 Joints with sealants a expansion joint b separating joint at window-wall junction C 2 . 1 9 Thermoplastic waterstops a external b internal

bon dioxide in a viscous state. They are used for sealing basement parkin g , parking decks and waste water systems, i .e. applications that require excellent adhesive qual ities and chemi­ cal resistance. Polyurethane sealants can also be used as an elastic adhesive. MS polymer sealants This reactive sealant type adheres to many dif­ ferent substrates and unites the properties of s i licone and polyurethane sealants. It is resist­ ant to u ltraviolet radiation, is free from solvents, has no smell and can mostly be used without any pretreatment, even in the case of damp sides to the joint. Many types of paint adhere to this type of sealant, even those containing sol­ vents. Acrylate sealants Sealants based on acrylate d ispersions exhi bit a plastic d eformation behaviour. The evapora­ tion of the dispersion water causes an acrylate sealant to shrink by up to 20%. They adhere to mineral and metal substrates , also plastics. Acrylate sealants are available in many d iffer­ ent colours and are used for rigid joints (dummy joints, construction joints) . They can be covered with certain, suitable types of paint. Polysulphide sealants Two-part polysulphide sealants u ndergo a chemically reactive curing process and exhibit an elastic deformation behaviour. During the hardening process they give off highly odorous sulphur compounds. Polysulphide sealants are used for joints in external walls or as secondary seals in the manufacture of insulating g lass un its. They adhere to a number of building materials such as plaster/render, timber, syn­ thetic materials and metals. Butyl sealants These sealants are based on butyl rubber and adhere to the majority of substrates. They remain permanently sticky and are used in the form of tapes or strips, e . g . in metalworkin g . Butyl sealants containing solvents c a n be injected into joints and moisten the substrate wel l .

1 43

I nsulating and sealing

Materials for sealing joints

Sealants (injectable, kneadable) Silicone (SI)

. acidic, neutral, alkaline (products given off)

Polyurethane (PUR)

. 1 -part, 2-part

MS polymer

. 1 -part

Acrylate (AY)

· ·

1 -part, 2-part

Butyl rubber

•

with and without solvents

·

Synthetic rubber

contains solvents, dispersant

Polysulphide

Linseed oil

Waterstops

desiccant (putty)

Waterstops

Waterstops made from PVC and synthetic rub­ ber are used wherever the maximum permissi­ ble total deformation of injected sealants is exceeded or perfect adherence to the sub­ strate cannot be guaranteed. Thermoplastic and elastomeric waterstops are concreted per­ manently in place in expansion and construc­ tion joints for in situ concrete. They p rovide a waterproof barrier across the joint. We distin­ guish between internal and external waterstops (fig . C 2 . 1 9) . Alternatively, expanding gaskets can be used in construction joints. In water­ proof concrete sheet metal waterstops can be used in construction joints if little movement is anticipated. Sealing strips

Sealing strips include backing strips made from PVC for construction joints and gaskets made from synthetic rubber to exclude rain and wind. Elastic seali n g strips made from elastom­ ers or soft polyurethane foams can achieve a degree of seal ing rangi n g from draughtproof to watertight depending on the surface character-

•

elastomer waterstop with/without profile plastic, self-adhesive elastic, non-self-adhesive

Polyvinyl chloride (PVC)

·

thermoplastic waterstop

Polyethylene (PE)

·

foam backing material (gasket)

Bentonite, EPDM

·

compressible strip

Steel

·

sheet metal waterstop

CompOSite

•

compressible tube

·

foam strip soaked in acrylic resin, precompressed aluminium foil strip single-/double-sided adhesive with profile

·

gaskets

•

• ·

Silicone (SI)

Ethylene-propylene- . gaskets diene rubber(EPDM)

C 2 .20

protect against moisture from the soil, non­ hydrostatic pressure and rising damp. These sealants comprise a binder of polymer-modi­ fied cement which is mixed on site to form a slurry. The slurry is min. 2 mm thick and can bridge over small cracks.

Waterproofing

Thick bitumen coatings One- and two-part plastic-modified thick bitu­ men coatings consist of a bitumen-plastic emulsion plus a cementitious powder. It is sprayed or spread on in at least two coats. Non-rotting fleece inlays bridge over any cracks. Thick bitumen coatings protect against moisture from the soi l , a build-up of seepage water and non-hydrostatic pressure, e . g . on roof surfaces and in wet interior areas.

Horizontal and vertical waterproofing systems protect the building against moisture. Horizon­ tal damp-proof courses (dpc) between founda­ tion and wal l consisting of one or more layers of flexible bitumen sheeting prevent water rising through capillary action to saturate the wall (ris­ ing damp ) . Vertical layers of waterproofing on external walls in contact with the soil must be i nstalled according to the loadi n g cases g iven in D I N 1 8 1 95 using the specified materials. Waterproofing of building components

In D I N 1 8 1 95 parts 4-7 the waterproofing of building components against ingress of water is d ivided into the following applications:

Bituminous coatings Coatings containing bitumen are applied as hot coatings and adhesive compounds. Hot coat­ i n g s consist of straight-run or blown bitumen, often provided with fibrous or stone dust fillers, which ensure weathering and impact resist­ ance. They are used for non-hydrostatic pres­ sure applications. Adhesive compounds are used to bond flexible sheetin g to the substrate. Flexible cement-based sealants Flexible cement-based sealants can be used to

1 44

Polyurethane (PUR)

istics of the sides of the joint and the compres­ sion of the sealing strip . Sealing gaskets are fit­ ted between movable components like doors and windows, and these also contribute to sound i nsulation.

waterproofing against moisture from the soi l , e . g . ground slabs o r basement walls waterproofin g against non-hydrostatic pres­ sure, e . g . precipitation, seepage water or splashing water on roofs, floors and wal l s in wet interior areas waterproofing against external hydrostatic pressure, e.g. parts of the building below the groundwater table waterproofing against internal hydrostatic pressure, e . g . swimming pools or drinking water reservoirs

C 2.21

Sealing strips, sealing gaskets

Flexible sheeting The application of flexible sheeting made from bitumen, polymer-modified bitumen, synthetic materials and rubber is very similar to the lay­ i n g of these materials on roofs. The materials fulfil similar tasks and are described in "The building envelope" (see p p . 1 25-27) . They ensure watertightness in the case of hydrostat­ ic pressure. Embossed sheet metal is used to strengthen the waterproofing in the case of more severe loads. Waterproofing materials on components in con­ tact with the soil must be protected against mechanical damage, e . g . by external thermal insulation, drainage mats or embossed sheets. Liquid-applied waterproofing systems These systems are suitable for waterproofing, for example, roofs and basements, primarily in the case of components with complicated geometries. Liquid-applied waterproofing sys­ tems based on flexible unsaturated polyester resins, flexible PMMA and flexible polyurethane resins undergo a reactive curing process after mixing their components or through contact with moisture in the air. They are applied by spreading, rolling or sprayin g . An inlay of fleece made from synthetic fi bres serves as reinforcement and bridges over any cracks. Together, they form a composite with the sub­ strate. The thickness of the waterproofing, usu­ ally applied in two coats, must be at least

I nsulating and sealing

Materials for waterproofing

Materials for watertightness Bitumen

• • · •

•

Plastics

•

·

•

undercoat adhesive compound, coating mastic asphalt bitumen and polymer-modified bitumen flexible sheeting plastic-modified thick bitumen coating flexible synthetic sheeting (also cold-applied self-adhesive) flexible rubber sheeting (also with self-adhesive coating) liquid-applied waterproofing systems

Metal

·

embossed sheet metal

Cement

·

cement-based sealants (rigid/flexible)

1 .5 mm, or 2 mm on trafficked roof surfaces. The European Technical Approval to ETAG 005 classifies the serviceability of l i q u i d-applied roof waterproofing systems according to per­ formance. It assumes a durability of up to 25 years depending on the particular application. Liquid-applied waterproofing materials in con­ junction with tiles and flags Polymer-modified cement, waterproofing mate­ rials based on polymer dispersions and flexible reaction resins on an epoxy or polyurethane base form the waterproofing layer for a com­ posite system using tiles and flags. This com­ posite is suitable for floors and walls in kitch­ ens, sanitary areas, balconies and foodstuffs­ processing operations depend i n g on the class of use ( I - IV) . The full bond between water­ proofing layer and substrate - partly with cloth inlays to bridge over cracks - plus the overly­ ing thin bed of adhesive for the tiles or flags provides three-fold protection against leaks. Airtightness, draughtproofing

We distinguish between internal and external layers when discussi n g airtightness and draughtproofing. Some insulating materials must be protected against airflows in order to guarantee the full insulating effect. In some cir­ cumstances the sheathing in a roof construc­ tion can, for example, protect the insulation against the wind when positioned on the out­ side of the insulation and provided with over­ lapping, bonded joints. However, such layers are not airtight and the joints, fixings and junc­ tions required to achieve airtightness mean that it is generally easier to attach an airtight layer to the warm, inner side of the construction. Open to diffusion, resistant to diffusion Depending on the type of construction, vapour permeability or impermeability is required. According to DIN 41 08-3 component layers with a water vapour diffusion equivalent air layer thickness Sd $; 0.5 m are regarded as open to diffusion, layers with Sd � 1 500 m are classed as resistant to diffusion and all values in between as diffusion-retardant. The terms airtight barrier, vapour barrier and vapour check corresponded to these figures.

Materials for draughtproofing

Materials for airtightness Film/foil

. polyethylene (PE) · based on polyamide, moisture­ adaptive • polyvinyl chloride (PVC) • aluminium (AI)

Flexible sheeting

·

PE cloth-reinforced sheathing, open to diffusion

Cardboard

•

bitumen felt

Boards Paper/cardboard

•

coated, impregnated

Boards

. gypsum boards with filled joints · aluminium-laminated insulation with tongue and groove joints over rafters

• •

wood fibre insulating board (WF) foamed insulating boards

Plaster/render

Diffusion-retardant layers are used i n the majority of cases (timber construction, roofs) . Basically, the construction should become more open to d iffusion from inside to outside so that outer layers do not hamper the trans­ port of moisture. Vapour checks must be installed airtight. The reverse is also true: air­ tight barriers can be used simultaneously as a vapour check, depend i n g on the material. Installation I n the case of sol id external walls a plaster fin­ ish over the entire internal wall surface achieves adequate airtightness in most instances. In lightweight constructions airtight­ ness is guaranteed by sheetin g or boards. The weaknesses in all types of construction can be found at the joints - between d i fferent parts of the airtight layer itself and also at junctions with other components; these are often the sources of leaks. This can be avoided by ensuring min. 1 00 mm laps in the case of sheeting plus addi­ tional sealing with cloth-reinforced adhesive tape (not carpet or parcel tape! ) . Cardboard a n d paper can b e used to provide an airtight or draughtproof layer by glueing them, like wallpaper, to inner linings. Next to the rafters they can be stapled or nailed in place, provided a double welt type of joint is formed. Seal i n g strips, joint sealants and com­ pressible strips can be used to create airtight joints with other components. In add ition to sheetin g and cardboard, thermal i nSUlation systems are available with a high water vapour diffusion resistance. Used properly, neither vapour barrier nor sheathing is req uired. But their tongue and groove connections must be glued airtight.

C 2.22 C 2.20 Systematic classification of materials for sealing joints C 2.21 Installing diffusion-retardant sheeting C 2.22 Systematic classification of materials for water­ proofing C 2.23 Physical parameters of sealants C 2.24 Physical parameters of waterproofing materials

Sealant

Linseed oil putty Oil-based putty, mod. Butyl Acrylate Polyurethane Polysulphide Silicone

Type of deformation

Permissible total de­ formation [%]

Durability [a]

0 plastic plastic plastic/elastic elastic elastic elastic

,,; 2 ,,; 5 5 - 20 1 0 -25 1 0 -25 1 5 -25

generally 1 0-25 (average) 12)

C 2.23 Waterproofing material

Foil/film aluminium PE PVC polyamide

Water vapour diffusion resistance [-]

virt. vapourtight 30000 20000 not constant

Flexible sheeting polymer-mod. bit 2 2 1 500 PE-C 30 000 PVC-P 20000 60000 EPDM 250 000 PIB ECB 90 000 CSM 25 000 Coatings thick bitumen, 1 -part 2000 thick bitumen, 2-part 4000 mastic asphalt virt. vapourtight reaction resins 20000 25 cement render waterproof concrete, C45/55 1 00

Material thickness [mm]

Sd

value

[m]

" 0.05 0.25 0.25

> 1 500 1 00 30 2.8/0.2'

5 1 .2 1 .2 1 .2 1 .5 1 .5 1 .2

86 36 24 1 20 225 1 35 30

4 4 ,, 1 5 1 .5 20

8 16 > 1 500 30 0.5

200

200

, The water vapour diffusion resistance depends on the humidity of the air; the values given here are valid for 50% and 80% relative humidity. 2 Flexible sheeting type PYE-PV 200 S4 has been selected here as an example. C 2.24

1 45

Building services

C 3.1

The development of what has recently become all-embracing building services began in the second half of the 1 9th century. Although water mains and drains for towns and cities had been known since ancient times, these were built for public faci l ities (e. g . fountains in Rome) and were intended for private buildings only in exceptional circumstances. The first public drains in Germany to connect private households to the waste-water system were b u i lt in 1 856 in Hamburg. Systems for supplying drinking water came later. The first complete systems for drinking water and waste water in multi-storey buildings appeared at the beginning of the 20th century. Demands on building services grew, and so over the course of time the provision of electric­ ity, gas and other media became necessary, also heatin g , ventilation and air condition i n g . Complex b u i l d i n g services installations with computer control have been available since the early 1 980s.

To do this, primary horizontal and vertical runs are grouped in d ucts and shafts respectively. Energy-savin g operation demands short runs, particu larly in the case of heating and hot-water pipes. The advantage of services installed in shafts or behind false walls - instead of being built in or cast in - is that they can be replaced and repaired without damaging walls, floors and other elements. D uring refurbishment or demolition work, serv­ ices in shafts or behind false wal l s can be d is­ mantled, removed , sorted and recycled. The followin g criteria are important when selecting materials or types of installation: ·

•

• • ·

Principles

C 3.1 C 3.2 C 3.3 C 3.4

1 46

Inmos microprocessor factory, Newport, UK, 1 987, Richard Rogers Applications for materials for drinking water sys­ tems Applications for materials for building drainage and waste-water systems Applications for materials for heating systems

In a detached house with masonry walls, 1 20 m2 of usable floor space and a standard level of comfort, the building services for water, waste water, heating and electricity add up to approx. 2.5% of the total mass of the build i n g . Even in laboratories and hospitals, with a high level of building services, this figure does not exceed 6%. Consequently, the potential for saving materials is only low in the case of building services. However, their influence on capital outlay and running costs is high. Furthermore, the integra­ tion of building services leads to d ifficulties in terms of disposal and recycling. Well organised and accurate planning of building services sys­ tems is therefore vital - the most economical instal lation is the one that is made superfluous by sound planning and desig n . A s building services are subject t o a shorter replacement cycle than load bearing compo­ nents, they should be designed in a way com­ mensurate with chan g i n g demands and easy replaceability.

• • • • • • ·

chemical and physical influences of the medi­ um being conveyed chemical and physical i nfluences of the ambient conditions susceptibil ity to furring maintenance options potential environmental or health impacts of the material during manufacture, usage and disposal adaptability to new user demands sound i nsulation, fire protection costs type of installation time required for installation l ife cycle assessment of materials aesthetic req u i rements

Only water, waste water, heating, ventilation, air conditioning and electrical installations are considered in the followin g . The other special areas of building services, e . g . escalators and lifts, waste disposal systems, special require­ ments for special buildings (e. g . hospitals) , are not considered in this book.

Building services

Drinking water systems

Drinking water is vital to l ife. All components that come into contact with drinking water must therefore comply with EU legislation, which requires that the drinking water must remain completely unaffected . This applies from the waterworks to the public and private water mains to the drinking water draw-off points. All materials and fittings (connectors, valves, etc.) for the systems must be approved for a continuous pressure of approx. 5 bar from the public water main and for peak pressures of max. 1 0 bar (Pn 1 0) . There are two principal factors that influence the suitability and durabil­ ity of a material for drinking water systems: hardness and pH value. The hardness of the water describes the content of magnesium car­ bonate and calcium carbonate (lime) in the water. The higher this content (i.e. the harder the water) , the more susceptible the system is to furring (incrustation), which can lead to pres­ sure losses, even blockages in the p i pes. With a neutral pH value of 7, there are no restrictions on material. But any marked deviations from this neutral value lead to an increased reac­ tivity of the water, which can have a damag i n g , usually corrosive, effect o n the material o f the pipe. The pH values permitted for drinking water according to European legislation lie between 6.5 and 9.5. Further factors are given in fig. 3.2.

extremely resistant to corrosion regardless of the composition of the drinking water. Stainless steel has no effect on the taste and does not affect the drinking water in any way. These pipes are very long-lasting and can also be recycled. When laying in the soil, stainless steel p ipes should be protected against external cor­ rosion. Copper pipes Accord ing to the provisions of Germany's cur­ rent Drinking Water Act (TwVO 2001 ) , copper p ipes are only approved for drinking water sys­ tems with a pH value > 7.4. I n the case of val­ ues > 7.0, the concentration of organic carbon in the drinking water (TOC value) may not exceed 1 .5 m g l l . If h igher concentrations of hydrogen ions occur in the water, copper can dissolve into the water and cause high concen­ trations in humans. As the water supply companies cannot guaran­ tee a consistent drinking water q uality (in terms of the pH value) over the lifetime of a b u i l d i n g 's water system , the use of copper p i pes for drinking water suppl ies is no longer recom­ mended. In the case of existin g copper pipe­ work, it may prove necessary to install a water treatment plant within the building in order to regulate the pH value and avoid any health hazards. Copper is a valuable raw material that can be recycled without any problems. Its straightforward , low-cost installation is a further advantage.

Metal pipes

Metal pipes achieve good durabi l ity. Despite their thin walls, they are very stable and can withstand some mechan ical damage, which simplifies installation. However, their vulnerabil­ ity to corrosion may need to be taken into account depending on the particular conditions. When adding metal p ipes to an existin g sys­ tem, it is essential to ensure that the metal matches that of the existing pipes, or to use a non-metal material because otherwise owing to the different electrochemical potentials of dif­ ferent metals, galvanic corrosion could occur. Galvanised steel pipes Steel pipes - seamless or welded - are galva­ nised inside and outside. As cadmium and zinc can dissolve out of the galvanic coating, such pipes should be used for service temperatures of max. 60°C only in order to avoid an unac­ ceptable concentration of metal ions in the drinking water. Galvanised steel p i pes are suit­ able for drinking water with a neutral to slightly alkaline pH value only; an acidic environment accelerates the dissolution of the zinc coating. Installed properly, galvanised steel pipes are very durable, provided the anti-corrosion coat­ ing is not damaged. But the high cost of instal­ lation restricts the use of these pipes consider­ ably. Stainless steel pipes Like galvanised steel p i pes, stainless steel pipes can be seamless or welded . They are

Lead pipes Lead pipes have been banned for new pipe­ work installations for many decades. In the light of the health hazards, the removal of all lead pipes must be considered as an urgent priority. Plastic pipes

Owin g to their low weight, plastic p i pes are easy to work and insta l l , but must be fixed to the structure at closer intervals than metal p i pes because they are less rigid. They are not electrically conductive and are therefore not suscepti ble to stray currents The smooth surface of plastic pipes makes them less vulnerable to furring within the cross­ section. They have a low flow resistance and cause l ittle noise. They are resistant to chemi­ cals and can be used for drinking water with any pH value. Non-toxicity and minimal influ­ ence on the quality of the water represent fur­ ther advantages. However, plastic p i pes are more vulnerable to mechanical damage than metal pipes and become brittle at low temperatures. Another disadvantage is their considerable thermal expansion, which calls for an appropriate installation in order to avoid irritating noises as the pipes expand and contract. Plastic pipes with plain ends can be glued or welded together. However, this i nvolves health hazards due to the substances used or the vapours given off when the plastic melts. Mechanical fittings (screw or compression

joints) are therefore available and have become well establ ished, also thanks to their d urab i l ity and reliability. As plastics can form ideal habitats for colonies of bacteria, germicidal metal salts are added to some drinking water p i pe materials. There is so far no evidence that such salts influence the quality of the drinking water. Untreated pipes must be i mpermeable to light and must be laid concealed in order to avoid attractin g bacteria. Plastic pipes belong to building materials class B (combustible) . They are less durable than metal pipes, but must last at least 50 years in order to obtain building authority approval. Pipes of high-density polyethylene (PE-HO) H i gh-density polyethylene can be used for cold-water pipework only, and therefore is mainly used for public water mains laid in the soi l and for the supply pipes to buildings. PE­ HO pipes are easy to work. The oxygen in drinking water (average content 3 g /l) can break down the molecular chains of the polymer under certain conditions. This can be prevented by adding an anti-oxidant (e.g. polynuclear phenols). The material's resistance to ultraviolet light can be i mproved by adding carbon black, which also dyes the material black. Pipes of cross-linked polyethylene (PE-X) The properties of cross-linked polyethylene are better than those of other polyethylene materials. Cross-linked polyethylene has an enhanced impact resistance and better permissible bend­ i n g , tensile and compressive strengths. As the long-time creep rupture strength of this material is also hig her, it is used for p ipes that must sat­ isfy particularly demanding bending require­ ments. PE-X is thermally stable and can be used for hot- or cold-water systems. Polyethylene p i pes are also available as p ipe­ in-pipe systems. Here, the p i pe (PE-X) carrying the water is installed in a corrugated protective pipe made from PE-HO, which can be supplied fully insulated for hot-water l ines. Pipes of polyvinyl chloride (PVC) PVC is a highly advanced synthetic material with almost ideal technical properties, but is sti ll problematic from the ecological and fire viewpoints. This plastic is mainly used in the form of post-chlorinated PVC-C when required for drinking water pipes. The material is stable up to 1 00°C and therefore may be used for both cold- and hot-water p i pes. U nplasticised PVC (PVC-U) contains no plasticisers. It is suit­ able for temperatures of max. 45°C and is therefore used for waste water only. Pipes of polypropylene (PP) I n pipework polypropylene is mainly used in the form of random copolymer PP-R. The proper­ ties of this material are very similar to those of polyethylene, but PP-R can withstand higher temperatures and is therefore also suitable for hot-water systems. It is harder than polyethy-

1 47

Building services

nected with fittings made from metal, PPSU or PVDF.

polishing, electroplatin g (e.g. chromium) or powder coatin g .

Composite pipes

Fittings

These are mUlti-layer p i pes whose layers are permanently bonded together. The inner l i n i n g carrying t h e water c a n be made from various plastics (PE-HD, PE-X, PB, PP) . This lining is embedded in a stabilising, welded aluminium pipe which is i n turn encased in a protective layer of plastic (PE-X, PB, PP) . Such p ipes unite the advantages of plastic and metal p ipes. The plastic inside and outside is not vulnerable to corrosion or furring and is resistant to chemi­ cals. Aluminium is resistant to diffusion and ensures good d imensional stability and low thermal expansion. Such pipes are low i n weight and easy to install because they are very stable but at the same time flexible.

Valves, meters etc. for water consist mainly of metal parts. However, plastics such as PP are often used for some of the mechanical parts inside, plus seals made from EPDM etc. The quantity of these materials is so low that it has no noticeable influence on the qual ity of the drinking water. Ceramics are being used and more and more for the seals in fittings because ceramics do not affect the drinking water in any way and are more d urable than synthetic mate­ rials.

Gunmetal fittings Like brass, gunmetal is an alloy of copper, tin (max. 1 1 %), zinc (max. 9%) , lead (max. 7%) and nickel (max. 2 .5%) . Gunmetal components can produced by casting only. They therefore have a rough surface, possibly exhibiting seg­ regation, shrinkage and pores. Such defects can lead to fai lures in the case of mechanical load i n g , excessive noise and leaks. Gunmetal is primarily used for larger fittings. Gunmetal and brass can be installed with metal pipes without fear of galvanic corrosion. These valuable alloys are readily recycled .

lene and is primarily used for supply p i pes and d istribution pipework.

Joint fittings for plastic pipes

The connectors for plastic pipes can be made from metal, PP-R, PVC-C, polysulphone (PPSU) or polyvinylidene fluoride (PVDF) . Generally, pipes of PP-R, PB and PVC-C require cou­ plings made from the same material as the pipe. PE-X and composite pipes can be con. I s for d ron ' k·ong Materoa water systems

Abbrevlatlon

Brass fittings Brass is suitable for high mechan ical loads and may be used (according to the 2001 Drinking Water Act) for drinking water fittings provided it contains no more than 3% lead in add ition to copper and zinc. Pressed or forged compo­ nents are better than cast ones because of their dense, homogeneous structure. The surfaces of brass components can be ground very smooth, which reduces flow resist­ ance and noise, and also permits further

App r1cations

nsta 11 atlon . in ...

Technical rules

Cl C

D 0 u

E

6

5°C. Granol ithic finish Wearing courses for industrial floors are fre­ q uently made from a cement screed with aggregates of metal, stone or emery or carbo­ rundum powder. These floors achieve com­ pressive strengths of up to 65 N /mm2. Terrazzo A cement screed finish made up of white cement, white and coloured aggregates (e.g. marble, porphyry, tuff) and pigments is known as terrazzo, which requires no further floor cov­ eri n g . The high cement content of the terrazzo mortar leads to severe shrinkage behaviour, which is why terrazzo floors are d ivided into bays measuring about 2 x 2 m . The self-weight of the approx. 20-30 mm thick layer is approx. 48 kg /m2. Terrazzo must be ground at least twice and is therefore a costly floor covering, but on the other hand very durable (fig . C 6.4 a) .

Calcium sulphate screed (CA) Screeds based on calcium sulphate were pre­ viously known as anhydrite screeds. Calcium sulphate screeds must be laid immediately after mixin g . They can accept loads five days after laying. Laying at temperatures < 5°C is not permitted. Owing to the slower curing proc­ ess in comparison to cement screeds, they achieve h i g h strengths and exhibit l ittle shrink­ age. These screeds are sensitive to moisture and therefore cannot be used outdoors, nor i n wet interior areas, even with falls a n d floor out­ lets. Additional waterproofing measures are necessary when laying these screeds on floors in d i rect contact with the soi l . Calcium sulphate screeds are often used in the form of self-levelling screeds. They can be laid without joints, even large areas, are easily and q uickly processed with site plant, and do not need to be compacted or floated. The surface can be ground and then the screed req u i res no further floor covering. Fig. C 6.4 d shows such a screed with a clay brick aggregate. Magnesite flooring (MA) Screeds can also be produced from a mixture of magnesium oxides and magnesium chloride solutions p l us further aggregates such as sand and pumice, but also organic aggregates, e . g . sawdust, cork, rubber, textile fibres a n d paper powder. The fast reaction time calls for careful work on site. Magnesite flooring is suitable for seamless, heavily loaded, bonded screeds (strengths up to 80 N/mm2) covering large areas, as are often necessary in industrial buildings. The temperature during laying must be > 5°C. Magnesite flooring can accept foot traffic after just two days, and is ready for its full loading after five days. However, it is not water-

.£

Floors

proof and therefore cannot be used for wet interior areas, nor outside. It can be protected by linseed oil and wax. Theoretically, magnes­ ite flooring can be returned to the raw materials life cycle, but in practice it is disposed of in landfill sites along with other mineral building materials. Flooring cement Densities < 1 600 kg / m3 can be achieved by adding aggregates such as sawdust to magne­ site flooring. The weight for a thickness of 1 220 mm is about 2 2 - 36 kg / m2 . The properties of flooring cements such as thermal conductivi­ ty, drying time and strength can be influenced by the mixing ratio. Despite their many advan­ tages, flooring cements are hardly used at present. They are elastic, feel warm underfoot, insulate against sound and the hardwearing surface can be used as a wearing course in itself. Coloured pigments can be added with lit­ tle effort. Mastic asphalt (AS) Bitumen is suitable as a binder for fine-grain aggregates such as stone dust, sand , chip­ pings and - possibly - gravel, which i n contrast to other aggregates must be dry before being added to the mixer. The binder content is about 8% instead of the approx. 1 6% for cement screeds. The climatic, chemical and mechanical resist­ ances depend on the particular mix, which must take into account the uti lisation plus ther­ mal and compressive loads. Mastic asphalt retains its thermoplastic behaviour even after laying, which means that heavy concentrated loads may leave imprints in the floor. The clas­ sification of mastic asphalt floors is therefore carried out according to hardness grades, measured by the penetration depth of a defined stamp . The applications are assigned to four hardness grades: G E 1 0 and GE 1 5 for heated rooms, GE 1 5 and G E 40 for unheated rooms, and GE40 and G E 1 00 for rooms with low tempera­ tures. When laid on insulating materials, mini­ mum requirements regarding compressive strength therefore apply. The laying temperature of approx. 250°C plac­ es considerable thermal demands on the underlying insulation. M i neral fibres, cork, perl­ ite, cellular glass and bitumen-impregnated wood-fibre insulating board are suitable insulat­ ing materials. Around the perimeter there is the risk of the impact sound insulation yieldi n g , so it is advisable to strengthen the edges to pre­ vent deformation in this zone. This is normally achieved by omitting the impact sound insula­ tion along the edges. The advantage of mastic asphalt for work on site is that it does not require any mechanical compaction and can be laid regardless of the weather. It can accept its fu ll load after just 2 -3 hours, is ready for laying further floor fin­ ishes once it has cooled, and requires no joints. Mastic asphalt is watertight, vapourtight,

not sensitive to water and not readily flammable (class B 1 ) . The optional addition of graphite powder affects the electrical conductivity of the asphalt and hence prevents electrostatic charges. Mastic asphalt achieves good sound insulation values and can be fully recycled. In contrast to popular opinion, mastic asphalt has no hazard­ ous i mpact on the environment, neither during laying nor in use (fig. C 6.4 c). Synthetic resin screed (SR) Screeds that use a synthetic resin as the binder and a quartz aggregate are suitable for heavily loaded industrial floors. Screeds with epoxy, polyester, methacrylate or polyurethane resins are laid in thicknesses of 5-1 0 mm. The aggre­ gates are quartz grains, but coloured pigments can also be added. Synthetic resin screeds can be ful ly loaded after seven days. They are practically vapour­ tight and easy to clean, although the rough sur­ face does require special cleaning equipment. M ixes with larger grains may satisfy impact sound insulation requirements. Electrical con­ ductivity can be achieved by adding graphite. The applications include production areas, abattoirs, laboratories, etc. Synthetic resin screeds can be recycled, but in practice sepa­ rating this thin layer from its substrate is uneco­ nomic (fig . C 6 . 4 e ) . Loam screed Loam screeds and tamped loam floors are among the oldest forms of screed and can be used without any further floor covering. Owing to their good moisture regulation properties, they are suitable for roof spaces, basements and rooms for storing foods and drinks. They are produced by mixing loam, water and organic aggregates such as wood c h i ppings, chaff and cow hair and then compacting this. The comparatively low strengths can be improved by adding cow blood and ash to the uppermost layer. Flooring-grade boards Various types of board are available for pro­ d ucing a floor finish in dry construction irre­ spective of the weather conditions. The advan­ tage is that no drying time is necessary. The boards can be used immediately after laying and any further floor finishes added immed iate­ ly. If the wearing layer is not g lued to the sub­ strate, the boards can be fed back into the raw materials l ife cycle. The boards are laid with staggered joints on, for example, loose fill or insulating materials, but can also be laid direct­ ly on existing floor coverings. Owin g to their minimal thickness, they are suitable for improv­ ing building performance characteristics and for upgrading old floors. Flooring-grade boards can increase the sound insulation of suspend­ ed floors by up to 28 dB. F i g . C 6.3 l ists further properties.

C 6.4

C 6.3 C 6.4

Physical parameters of subfloors Screeds and subfloors a terrazzo b flooring cement c mastic asphalt as wearing course d calcium sulphate screed with clay brick aggregate e synthetic resin screed f cement screed

1 73

Floors

Screeds and subfloors Layers • for origin of data see "Life cycle assessments", p. 1 00

PEI primary energy non-renewable [MJ]

PEI primary energy renewable [MJ]

GWP global warming [kg C02eq]

oop

ozone depletion [kg R 1 1 eq]

AP acidification [kg S02 eq]

EP eutrophi­ cation [kg PO, eq]

pocP summer smog [kg C2H, eq]

203

3.8

18

o

0.076

0.0073

0.0070

C======::JI

IC======::J

0.026

0.001 8

Mortar screeds and wet subfloors cement screed cement screed (CT 20-8 50), 50 mm building paper, 0.2 mm mineral-fibre insulation, 20/1 5 mm calcium sulphate screed

71

2.2

calcium sulphate screed (CA 20-8 50). 50 mm building paper, 0.2 mm mineral-fibre insulation, 20/1 5 mm mastic asphalt

5.8

o

=

443

5.1

11

o

o

0.064

mastic asphalt, 25 mm building paper, 0.2 mm coconut board, 10 mm magnesite flooring

21 1

3.6

14

0.001 0

o

0.038

magnesite flooring (MA CT C 50-V 25 F). 25 mm mineral-fibre insulation 25/20 mm

0.0069

0.0 1 3

==,

=== :::::::1 lC

0.0035

0.01 3

=

Dry subfloors clay tiles clay tiles, tile adhesive, 20 mm mineral-fibre insulation 25/20 mm fibrous plasterboard fibrous plasterboard, 2 layers, 20 mm mineral-fibre insulation, 25/20 mm particleboard* particleboard (P1 ) , glued, 19 mm mineral-fibre insulation, 20/1 5 mm polyethylene fleece (PE). 1 mm C 6.5

The following materials are suitable: · • • · •

particleboards wood-fibre composite boards plasterboards fibrous plasterboards composite boards of gypsum and i nsulating materials

Particleboards Flooring-grade particle boards have tongue and g roove joints on all sides, which ensure tight joints after being g lued and a flush upper sur­ face. Thicknesses of 1 0 to 70 mm are possible, with the minimum thickness for normal imposed loads being 1 9-22 mm. Laying is covered by DIN 68 77 1 . The boards can be laid o n existin g floors, battens or a d r y fill, e . g . perlite . The applications for particle boards bonded with synthetic resin are limited to rooms with low moisture loads. But the heavier, cement­ bonded boards are resistant to the effects of moisture and are also not readily flammable (class B 2 ) . Vapourtight sheeting should not b e used when laying the boards over timber joist floors because the sheeting hinders the vapour d iffu­ sion through the construction, which can lead to rotting of the timber. Plasterboards and fibrous plasterboards Three layers glued together with rebated joints

1 74

and generous overlaps are available for use as flooring. The board thickness lies between 20 and 25 mm. The advantages of these boards compared to particleboards are their better d imensional stabil ity, better sound insulation values (owing to the higher self-weight) and the building materials class A2 rating (incombusti­ ble) . They are laid in a similar way to particle­ boards and are frequently bonded d i rectly to a layer of insu lation. Clay tile subfloor Clay tiles with a facing qual ity and tongue and g roove joints are avai lable as 20 mm thick sol i d or a s 40 - 50 mm thick slotted versions. They are glued in place floating on a layer of insulation. The thicker tiles are intended for lay­ ing in a thick bed of tile adhesive or sand. Owing to their temperature and moisture regu­ lating properties, they are especially suitable for storage rooms. Sprun g floors For some special applications such as sports and dance halls, wooden floorboards are sup­ ported elastically on the underlying construc­ tion. We d istinguish between floors supported over their full area on orthogonal layers of boards, and floors supported at individual points on foamed materials.

Floor coverings

The materia l , appearance, texture and colour of the floor covering have a considerable influ­ ence on our perception of an i nterior. Besides functional considerations, the aesthetic con­ cept determines the choice of floor finish. Appearance and sound i nsulation also contrib­ ute substantially to our subjective evaluation of an agreeable interior atmosphere. Selecting the visual appearance of a floor cov­ ering can be based on various concepts. For example, the idea could be to create the illu­ sion of walls, floor and ceiling cast from one mou l d , but it could equally wel l involve a stark contrast between materials and/or colours. It is frequently the case that walls and ceiling form a neutral background for the finishes and fit­ tings of the user. U niform floor coverings can emphasise relationships between different areas, e . g . between internal and external zones, and different coverings within a room can define d ifferent functional zones. The treat­ ment of the surface demands particular atten­ tion. In contrast to a matt, rugged surface fin­ ish, the appearance of a gloss finish can change with the angle of incident daylight. A huge range of materials, products and prod­ uct variations (colour, q uality, texture and other characteristics) is avai lable to satisfy the multi­ tude of requirements (fig . C 6.7). In addition to the normal parameters for choosing a building

Floors

I II III

= = =

Cement screeds • granolithic . terrazzo

particularly warm underfoot adequately warm underfoot no longer adequately warm underfoot

clay brk. agg. scd.

I n contrast to the heat penetration factor, the thermal energy lost from a surface at a temper­ ature of 33°C d uring 1 or 1 0 min was hitherto used as the standard ( D I N 52 6 1 4) . But whether warm underfoot or not is a - to a certain extent subjective - factor of the overall comfort of an interior that cannot be entirely covered by a physically quantifiable figure. I n the case of floor coverings that are perceived as particular­ ly warm underfoot, a feeling of comfort is still possible even when the temperature of the inte­ rior air is 1 -2°C lower.

C 6.6 C 6.5 C 6.6 C 6.7

Life cycle assessment data for screeds and subfloors Marble floor, Santa Maria della Salute, Venice, Italy, 1 683, Baldassare Longhena Systematic classification of floor coverings

material, there are other requirements specific to floors. Building design The first parameters concern the existin g build­ ing or the specification. Self-weight and depth of construction must be compatible with the compressive strength and hence the load-car­ rying capacity of the underlying structure and the framework cond itions of the interior, e . g . levels of adjoining floors. The underlying construction is also important. Underfloor heating and raised floors are not compatible with every type of floor covering. I n order to prevent entrapped moisture in con­ crete slabs and screeds causing damage, flooring-layers must check the residual mois­ ture content of the substrate prior to laying floor finishes. Building performance Moisture control, sound i nsulation and thermal insulation requirements may restrict the choice of floor covering. Fig. C 6.20 (see p . 1 84) shows comparative values. Heat conduction, perceived temperature Loss of heat from the human body due to con­ tact with a floor finish leads to the floor finish feeling cold. We classify floor coverings according to the following system :

Electrostatic behaviour Electrical charges can accumulate in a person as he or she walks across an insu lating floor coveri n g , and these can lead to unpleasant discharges upon touching earthed metal objects such as door handles, safety barriers, even computers. Humidity, footwear material and clothes influence this process. Sensitive electronic equipment can be damaged by the ensuing h i g h voltages. D I N 54 346 d ivides floor coverings into three classes accordi n g to their electrostatic proper­ ties

Class 1 covers the so-called antistatic floor coverings; i . e . the charge that builds up i n persons walking across such floors is max. 2.0 kV. This is the specification for all rooms with electronic equipment (also residential accommodation) . • Class 2 is necessary to prevent damage in rooms with sensitive equipment. Suitable floor coverings are designated as conductive. Class 3 is achieved by the especially conduc­ tive floor coverings essential for safety rea­ sons in operating theatres, research estab­ l ishments and production faci l ities (protection for persons and equipment, explosion protec­ tion).

Finished subfloors

synthetic resin coating

natural stone Stone

Non-slip properties Germany's employers' liability insurance asso­ ciations specify minimum req u i rements for floor coverings for safety reasons (publication BGR 1 81 ) . The parameters for this are the surface texture (classes R 9-R 1 3) and the liquid d is­ placement factor (classes V 2 -V 1 0) .

cement-bonded recon. stone bitumen-bonded tiles

Ceramics

o u

8

clay bricks stoneware earthenware split-face blocks eng. bricks terracotta

glass mosaic tiles

-=

laminated glass Glass and metal

embossed sheet metal etc. open mesh floor

Wood and wood­ based products

floorboards wood-block fir. end-grain wood­ blk. parquet squares real wood lam. aSB plywood

•

Usage The suitabil ity of floor coverings for certain uses are regulated by hygiene, industrial safety (non-sl i p ) , electrical conductivity and many other aspects.

mastic asphalt tamped loam

·

In practice it is vital to ensure that the floor cov­ erings are attached to conductive undercoats with suitable adhesives. Copper strips incorpo­ rated in the floor (and connected to a suitable earthing system) g uarantee that any voltages that may build up can be discharged safely.

flooring cement

Laminated floor coverings

o u

Made from natural materials

o

o -=

C � 'ii) Ql 0:

35° is not slippery for persons under normal conditions, and V4 means that a volume of liquid equal to 4 cm3/ dm2 can be accommodated by the surface structure without forming a continuous film of moisture, There are three classes (A-C) for barefoot areas (e,g, swimming pools) ; class C is the highest safety standard , Chair castors Product data sheets on floor coverings always contain details of the product's suitability for chair castors in offices, The castor and floor covering materials must be compatible, Castor type W is soft and therefore suitable for hard floor coverings, whereas type H is hard and better for soft floor coverings, Interior climate Floor coverings can have a serious influence on the interior climate, The materials and adhe­ sives plus cleaning and care products must be chosen carefully in order to rule out - as far as possible - any risk of hazardous substances, Sustainability Floor coverings are subject to high mechanical loads, Accordingly, wearing characteristics play a key role in their selection, There is a D I N classification for contract ratings for various groups of coverings (fig, C 6,20) , Floor coverings should not change colour when exposed to d i rect sunlight. Changes in the material structure due to mechanical loads and moisture or temperature fluctuations can cause fissures (wood-block flooring) or tension cracks, Owing to the necessity of regular care over the entire lifetime of a floor covering, the cost of upkeep of some floor finishes is higher than the capital outlay,

Properties Owin g to their good wearing resistance, stone Natural and reconstituted stone, ceramics, floor coverings are always first choice if, despite glass, metal, wood and wood-based products heavy loads, a long service life can be antici­ make up the group of hard floor coverings, pated to offset their high cost. The surface The large range of man-made tiles and flags treatment, which influences abrasion and non­ can be differentiated accord ing to the binder slip characteristics, is very important (figs used: cement, synthetic resin, bitumen and C 6 , 9 a and b), The spectrum ranges from clay (ceramics) , - porous stone types with rough surfaces (e,g, Flags and tiles made from materials with a min­ sandstone) to smooth, polished marble or gran­ eral binder can be laid in a 1 5-20 mm mortar ite, The suitabil ity of a type of stone and its sur­ bed (thick-bed method) when used as a floor face treatment for a certain application must be coverin g , There should be no excess moisture verified by standardised ( D I N) test certificates, in the underlying components because this in Sedimentary rocks with porous, unsealed sur­ combination with the alkaline mortar can dis­ faces are vulnerable to fluids such as fats, solve some constituents in stone and cause wine, etc, And acidic substances (e,g, vinegar) unattractive discoloration, When using the thin­ can cause chemical reactions that lead to d is­ coloration, It is advisable to request the appro­ bed laying method, the flags and tiles used must exhi bit better d i mensional stability and the priate test certificates, substrate must be more accurate, which is usu­ Some types of stone such as quartzite, sand­ ally achieved with a levelling layer, This method stone and gneiss have high a coefficient of is also suitable for laying flooring-grade thermal expansion, All types of natural stone belong to building materials class A 1 (incom­ boards, The choice of mortar or tile adhesive depends on the use of the area, the substrate bustible), Stone floor coverings are perceived and the loads anticipated, as cold underfoot. Owing to their high thermal conductivity and heat storage capacity, stone Joints is a good choice in conjunction with underfloor The grouting of joints between stone or ceramic heatin g , Stone floor coverings without an insu­ flags and tiles with a fine cement mortar should lating layer make no contribution to impact not be carried out too soon; a drying time of 7sound insulation, 1 4 days should be allowed for, Some types of stone susceptible to discoloration req u i re a Planning advice rapid-hardening mortar, Thin (approx, 1 0 mm) stone tiles ground flat The size, pattern and direction of joints are criti­ can be laid l i ke ceramic tiles in a thin bed of cal for the final appearance of a hard floor cov­ adhesive, However, flags 20-50 mm thick in eri n g , A plan that also takes into account the formats up to 300 x 600 mm are more common, junctions with vertical components is vital, and these require a mortar bed, The low tensile especially for non-orthogonal layouts, strength of stone means that the thickness increases with the plan size , As the production Natural stone of larger formats results in more wastage, the The variety of d ifferent types of stone available costs increase disproportionately, Cement mor­ is enormous, As they can exhi bit d ifferent tex­ tar plus quartz sand is used for filling the joints, tures and colours depending on their orig i n , The colour of the joints can be matched to that even thoug h their composition is identical, of the stone floor covering by mixing in stone stone types are often marketed with particular dust or pigments, product names, which complicates any review, Some cleaning products attack some of the Hard floor coverings

C 6,8

C 6,9

a

b

c

d C 6,8

1 76

Tile and flag layouts (examples) a crazy paving b random stretcher pattern c alternating grid and stretcher pattern d grid pattern Examples of hard floor coverings a natural stone (coarse) b natural stone (fine, dressed) c reconstituted stone d stone with synthetic resin binder e mastic asphalt tiles f engineering bricks g ceramic tiles h glass mosaic tiles

Floors

constituents in stone (e.g. l ime) . It is therefore essential to follow the recommendations of the suppliers. Special attention must be paid to a stone's chemical resistance to acids and dis­ solved salts when the stone is being used for external and entrance zones. Flags and payers with a cement binder

Precasting plants fabricate flags and pavers (reconstituted stone) from large blocks, which are then sawn and ground after curing (fi g . C 6.9 c) . Cement is used a s t h e binder. The great variety of products is due to the large selection of aggregates available, e . g . stone, gravel , pigments, glass, etc. The improper use of glass aggregates has led to problems in the past. Besides the so-called single layer method, two­ layer elements can be manufactured by press­ ing, and this permits the use of a surface finish with a more expensive aggregate. Surface treatments and properties are similar to those of concrete, or rather the aggregates. The standard formats are 250 x 250 x 22 mm, 300 x 300 x 27 mm and 500 x 500 x 50 mm; larger, custom formats are also possible. These flags and pavers are usually laid in a thick bed of mortar. They represent a less expensive alternative to natural stone products and are also suitable for use in conjunction with under­ floor heating. Flags with a synthetic resin binder

These products are made from synthetic resins and a stone granu late. The 1 5 - 20 mm thick flags are cut from large blocks of cured materi­ al and the top surface is pol ished afterwards. They are simi lar in appearance to the reconsti­ tuted stone flags, some even look remarkably like natural stone (especially the conglomerate rocks) (fig . C 6.9 d ) . The properties of the bind­ er enable thinner flags to be produced than with reconstituted stone. Large formats up to 1 800 x 3800 mm are available, but also spe­ cially formed components for washing areas etc. The surface is less hardwearing than com­ parable natural stone. Most of these products are not frost-resistant and belong to building materials class B1 (not read ily flammable) . These represent a less expensive alternative to natural stone products and have almost identi­ cal properties, but a lower chemical resistance to acids, stain removers and similar products. Tiles with a bitumen binder

Mastic asphalt tiles are available in simi lar for­ mats to tiles made with a cement binder. The mixing ratios can be adjusted so that the prop­ erties are simi lar to those of a mastic asphalt floor (see p. 1 73) . The range on offer includes three types of pressed asphalt tiles: standard, mineral oils- and acid-resistant, and terrazzo asphalt tiles, which combine the properties of reconstituted stone and mastic asphalt. Owing to their good resistance to chemical effects, mineral oils, facts, petrol , etc. , mastic asphalt tiles are especially suitable for trade fair and

industrial buildings. A mastic asphalt floor cov­ ering requires protection against rising damp. They are weather- and frost-resistant (fi g . C 6 . g e ) . Ceramic products

The group of ceramic floor coverings includes stoneware and earthenware products, ceramic split-face blocks, engineering bricks (fi g . C 6.9f) and brick slips. Fine ceramic tiles The standard sizes are 1 00 x 1 00 mm to 300 x 900 mm, but larger, custom sizes are also possible, as wel l as stoneware and g lass products as small as 1 0 x 1 0 mm. The non-slip characteristics of earthenware products are only limited , and they are not frost-resistant. Stoneware products, on the other han d , have a denser body ( i . e . clay product without g laze) , which even without a g laze are also suitable as floor coverings. Glazes are divided into four wearing groups,. However, grains of sand adhering to the soles of shoes can scratch all glazed surfaces, which is why they are not suitable for heavily traf­ ficked areas. Coarse ceramic floor coverings Split-face blocks are produced by extrusion. The standard formats are 240 x 1 1 5 mm and 1 94 x 94 mm. Split-face slips are narrower, e . g , 240 x 52 mm o r 240 x 7 3 mm. Engineering bricks for floors are manufactured by pressing. Besides square formats based on the 300 mm module, there are also many products that do not correspond to the modular d i mensions. Properties and planning advice Ceramic floor coverings are very hardwearin g a n d long-lastin g . They are incombusti ble (building materials class A 1 ) , thermally stable, exhibit a good heat storage capacity and do not rot. Frost-resistant products must be select­ ed for external applications. Both the thick- and thin-bed methods of laying can be used. Ceramic floor finishes are also ideal for use in conjunction with underfloor heating. Design options Besides the surface finish of the tile itself, the network of joints presents another significant design option. A plan of the tile layout should be produced in order to coordinate layout, cuttin g and fixtures, and to help avoid awkward small cuts, which are a disadvantage both visual ly and technical­ ly. The tiles can be laid in diagonal or orthogo­ nal patterns, with contrasting strips, edges, arrangements and many more ideas. I nd ividual designs and patterns are possible with l ittle effort.

h

C 6.9 1 77

Floors

r---f-r---r---r---r----

I a

b

Floor coverings of wood and wood- based products

c

• • •

Wooden floorboards were the principal cover­ ing to timber joist floors until wel l i nto the 20th century. The softwoods used in most cases are less hardwearing than hardwoods with their very durable surfaces. All wooden floors feel warm underfoot, exhi bit good hygiene proper­ ties and require little maintenance. For details of the advantages of this renewable raw material, please refer to "Wood and wood­ based products", p. 75. Design options

Owing to the multitude of possibilities, wooden floor coverings can create a vast ran g e of dif­ ferent interior atmospheres. Species of wood, formats, method of laying and surface treat­ ment are the parameters that affect the appear­ ance of a wooden floor. Species of wood The appearance of the floor covering is essen­ tially determined by the species of wood (see "Wood and wood-based products", p. 69) . When choosing wood for parquet flooring, for instance, it is the texture or grain that is critical. For example, the term "exquisite" in oak par­ quet flooring describes equivalent pieces of wood that have been very carefully selected, whereas "rustic" can contain vigorous colour variations, and "standard" l ies somewhere between the two. Samples should be request­ ed to illustrate the d ifference in the overall appearance of a floor coveri n g . Origin From the ecological viewpoint, indigenous spe­ cies should be preferred over exotic varieties. The FSC (Forest Stewardship Council) certifi­ cate - also available for products from over­ seas - guarantees that the rules of sustainable forestry are upheld. Formats Wooden floor coverings can be d ivided into the following groups depending on the proportion of solid timber and the sizes of the components:

• •

I

I

I

d

floorboards wood-block flooring mosaic parquet real wood parquet laminate end-grain wood-block flooring

Laminated floors do not include any sol id tim­ ber and are therefore dealt with on p. 1 79.

Floorboards Floorboards are cut from solid timber and are usually laid in lengths to match the width of the room. Lengths up to 6 m and widths up to 350 mm are available (fi g . C 6. 1 2 a) . When lay­ ing on battens and strips of insulation, a screed is not essential. Floorboards are not the same as the so-called rustic-look floorboards availa­ ble these days, which are made from a multi­ layer wood-based product and therefore fall into the category of real wood parquet laminate (see below) . Solid wood-block flooring Sol i d wood-block flooring is max. 22 mm thick and available in squares or separate blocks. The blocks have a groove on all sides into which loose tongues are g lued to join the strips to form a complete floor. Some versions are available with alternating tongue and groove joints. The squares (or "ti les") are blocks sup­ plied already g lued together into larger for­ mats, up to 1 x 1 m depending on the planned pattern. D ifferent species of wood can be com­ bined within the squares to form complex pat­ terns (figs C 6. 1 2 c and d ) . Wood-block flooring is g lued to flat substrates over its full area; but on a floating subfloor of timber or wood-based products, the flooring is secret-nailed in the joints. The laying options are almost endless: ship's deck, brick half-bond, straight basket and d iagonal basket form orthogonal patterns. The d imensional tolerances of building components can lead to acute-angled cuts with these floor finishes. Herringbone, double herringbone and chevron patterns are laid at an angle of 45° to the enclosing walls. The patterns used with wood-block squares include Bordeaux, Monti-

e

cello and Versailles with and without borders and/or traml ines. 10 mm solid wood-block flooring The thinner material is an alternative to solid wood-block flooring and is suitable for refur­ bishment work or as a substitute for floor cover­ ings of similar thickness (ceramic tiles) . A fab­ ric or paper mesh backing holds together the 1 0 mm thick blocks to ease the full-bond gluing to the substrate. The finished floor cannot be distinguished from standard wood-block flooring.

Mosaic parquet, block-an-edge parquet Smaller blocks of wood 8 mm thick correspond in principle to the 1 0 mm solid wood-block floorin g . The length of the blocks is l imited to max. 1 65 mm. The squares supplied on a paper mesh backing consist of, for example, four bays each comprising five blocks, which form the characteristic basket weave of five-fin­ ger pattern. Block-on-edge parquet is very hardwearing and consists of a mosaic of blocks on edge to form a wearing course 1 824 mm thick (fi gs C 6. 1 2 e and f) . Real wood parquet laminate flooring I n order to avoid shrinkage of the wood and open joints in the flooring, mUlti-layer assem­ b l ies - mostly three cross-banded plies - of wood-block flooring are available. Both individ­ ual blocks and also larger elements (to simpl ify

b

1 78

C 6.10

Floors

Wooden flooring format C 6. 1 0 Examples of wood-block flooring a ship's deck b brick half-bond c herring bone d square basket e diagonal basket f parquet floor squares C 6.1 1 Dimensions of wooden floor coverings C 6. 1 2 Types of parquet flooring a ship's deck b herringbone c parquet floor squares d marquetry parquet e mosaic parquet, square basket pattern f mosaic parquet, parallel pattern g end-grain wood-block h bamboo parquet, ship's deck pattern

Thickness of wearing course [mm]

Floorboards

( solid ) wood-block flooring

1 4 -22

Thickness of material [mm]

Visible format, max. [mm]

1 5.5-40

up to 6000 x 1 75

1 4 -22

up to 600 x SO

mosaic parquet

S

S

up to 1 65 x 25

1 0 mm solid wood-block flooring

10

10

n.a.

block-on-edge parquet

1 S -24

1 S-24

1 30-1 60 x S

end-grain wood-block flooring

22-60

22-60

1 3S x 69 650 x 50, 300 -1 200 x 60

real wood parquet laminate flooring

3-S

7 - 26

rustic-look floorboards

3-S

7 - 26

oriented strand board

1 0 -1 2

10-12

2500 x 1 250

,;: 2

7-10

1 208 x 1 94

veneered boards

up to 3000 x 200

C 6.1 1

laying ) , comprising several blocks to form a wearing course, are available. The wearing course consists of hardwood at least 2 mm thick, the underlying plies softwood or wood­ based products, making up a total thickness of - normally - 1 5 mm. The surface treatment is carried out in the factory, further working on site is not possible. This type of flooring is laid floating on a layer of impact sound i nsulation, but can also be g lued or secret-nailed to a sub­ floor.

can be repeated several times during the l ife­ time of the floorin g . A damp-proof membrane to protect against moisture is necessary when wooden floor cov­ erings are laid on floors in contact with the soi l . A n expansion joint is necessary between float­ ing wood finishes and all vertical components.

End-grain wood-block flooring Cross-cut sharp-edged blocks with a robust end-grain surface are laid d i rectly on the sub­ strate (fi g . C 6 . 1 2 g) . Species such as Scots pine, larch, spruce or oak are available in thick­ nesses from 22 to 80 mm. We distin guish between two contract ratings: GE for commer­ cial uses, RE for prestig ious purposes.

Surface finish Sealing materials, waxes or impregnation g ive wooden surfaces the necessary protection against moisture and soi l i n g . Coating materials, e . g . based on acrylic resin dispersion, alkyd resin, two-part systems based on polyurethane resin or made from animal or vegetable oils and waxes, can be considered (see "Surfaces and coatings", p. 1 95). Wooden floors remain attractive for a long time; minor imprints and scratches are generally regarded as agreeable signs of wear.

Production and processing Wooden floor coverings are manufactured on an industrial scale. Depending on the type of flooring , the dried and roughly sized pieces of timber are glued to other layers and/or pre­ pared for laying. With the exception of real wood parquet laminate flooring , the surface treatment is carried out after laying. Floor cov­ erings of solid timber are sanded to produce a flat surface after laying and are then treated to protect them . The sanding and sealing process

Properties Although timber basically belongs to build ing materials class B2, some wooden floor cover­ ings, e . g . oak parquet flooring, achieve class B1 (see fig . C 6.20) . Once installed, the hygroscopic behaviour of timber helps to regulate the interior climate. The moisture content of the timber adjusts along with changes in the relative humid ity of the interior air. The moisture absorbed by the timber leads to changes in size, which in the

d

case of severe fluctuations in the interior cli­ mate can result in visible, open joints in the floor covering. Applications The most common species of wood for flooring are oak, beech, maple, alder, ash, cherry, larch and spruce. The less well-known varieties i nclude bamboo, coconut palm and olive, all of which have good Brinell hardness values and are therefore ideal as floor coverings, providing an interestin g surface finish (fig . C 6. 1 2 h). Bamboo I n botanical terms the bamboo plant is a grass, not a tree. The plant's fast g rowth produces a great quantity of biomass. Bamboo's outstand­ ing material properties, e . g . Iow weight, high strength i n compression, tension and bending, plus its relatively easy workability, make it a very useful building material. Bamboo parquet flooring is very long-lasting and harder than oak or maple.

Laminated floors

Laminated floors form a separate group of floor coverings. In most cases the surface finish imi­ tates a wooden floor covering (fi g . C 6. 1 3) . The wearing course consists of HPL (high-pressure laminate) . A layer of transparent melamine

h

C 6. 1 2

1 79

Floors

resin protects the decorative finish printed on paper. The core of the board is made up of several layers of paper and synthetic resin pressed together. The backing is usually a wood-based board, usually wood fibreboard, particleboard or MDF. A backin g paper on the underside prevents the board distorting. Prod­ ucts made exclusively from HPL are moisture­ resistant (solid laminate ) . Owing to their thick­ ness of just 7 mm, laminated floors are fre­ quently used for refurbishment work. Laminated floors are very hardweari n g , but are not antistatic and - apart from solid laminate are susceptible to moisture. Plastic sheeting can be used to protect moisture stemming from vapour d iffusion and moisture trapped in miner­ al building materials. Such floors can be laid floating or firmly bond­ ed to the substrate. Some products have spe­ cially shaped edges which enable the ind ividu­ al pieces to be c l i pped together without the need for any adhesive. As small d ifferences in level at the joints between the elements can become visible when viewed agai nst the light, laminated floors are laid parallel with the d i rec­ tion of the incoming l i g ht. Laminated floors can­ not be refurbished or repaired.

the smoke development (2 development) .

=

moderate smoke

Cork

Feel underfoot and comfort are among the great advantages of cork floors (fi g . C 6. 1 4 b) . For details of impact and airborne sound insu­ lation, please refer to " I nsulating and sealing", p . 1 34. Cork floor coverings are available in two ver­ sions - as cork parquet flooring and as real cork parquet laminate flooring. Cork parquet flooring is glued to the substrate over its full area. Data sheets 3-7 published by the TKB (Technical Commission on Building Adhesives) are helpful . However, real cork parquet lami­ nate flooring is laid floating. Cork floor cover­ ings are usually 4 mm thick, but in exceptional cases can be up to 8 mm thick. Without a suita­ ble surface treatment (sealing or waxing) cork is very quickly soiled. By contrast, PVC-coated cork floor coverings req u i re only minimal care and no further surface treatment, and even meet the req u i rements for chair castors. Clean­ ing and care are reduced to vacuuming and/or wiping with a wet cloth . Cork floor coverings can be recycled as insulating materials. Rubber and synthetic rubber

Resilient floor coverings

Resilient floor coverings are those floor cover­ ings made from synthetic or natural materials that provide a dense, smooth finished surface. Many types are offered in 2 m wide rolls, others in the form of square tiles. D ispersion, solvent, contact and reaction resin adhesives are suita­ ble for the full-bond laying, which is essential. Resilient floor coverings are classified by EN 685 according to their wearing q ualities. The main groups 2 1 -23 are suitable for resi­ dential applications, 31 -34 for commercial and public buildings, and 4 1 - 43 for industrial build­ ings. There is a coding system for identifying the fire behaviour of these products ( D I N EN 1 3 501 - 1 ) : in "5.2", for example, the first d i g it represents the building materials class (5 not read ily flammable) , and the second d i g it designates =

C 6. 1 3

1 80

a

Natural rubber obtained from tropical rubber trees is hard ly offered i n its pure form any more. Synthetic rubber is obtained from crude oil in about 20 d ifferent varieties. Various types of rubber - also natural rubber - are mixed together for floor coverings. Vulcanisation cre­ ates a permanently resilient polymer from the raw materials. These floor coverings are available in 2 m wide rolls or 500 x 500 mm tiles. RAL RG 806 stipu­ lates the quality guidelines for this type of floor covering. Rubber floor coverings are hardwearin g , per­ manently resilient, d i rt-repellent, non-slip, anti­ static and resistant to oils, fats, chemicals and Cigarette burns. They also contain no hazard­ ous chemicals. Rubber is easy to work and thanks to its hardwearing qualities and good impact sound insulation properties (improve­ ment from 8 to 20 dB) is a good choice for pub-

b

c

l i c b u i l d i ngs (fi g . C 6 . 1 4c) . Some products are resistant to ultraviolet light and can also be used outdoors. Honeycomb rubber mats or products made from rubber strips fitted into aluminium sections are su itable for entrance zones. Rubber floor coverings belong to building materials class B 1 , and the normal thickness is 2-5 mm. Linoleum

Linoleum, from the Latin linum ( flax) and oleum ( oil), is a man-made product made from renewable raw materials (fig. C 6. 1 4 a) . The invention of li noleum in 1 863 b y the Eng­ lishman Frederick Walton marked the begin­ ning of manufactured floor coverings. For a long time l i noleum dominated the market for resil ient floor coverings, before - starting in the mid-20th century - PVC gradually took over as the market leader. =

=

Production Linoleum is produced by oxidising linseed oil and mixing it with a natural hardener - colopho­ nium (or common rosin); the mixing ratio is about 4 : 1 . This binder is mixed with roughly equal parts of sawdust and stone dust (chalk) plus cork powder, which is responsible for the elasticity and insulating properties. Pigments are added to g ive the desired colour. The raw material is then calendered (pressed between rollers) in several passes onto a textile (jute or g lass fibre) backin g , dried for several weeks at high temperatures in a kiln and subsequently cut i nto rolls or tiles. Surface finish The natural colour of linoleum is a mottled beige-brown. Pigments are added to provide a whole range of colours from pastel to bol d , with various textures. The surface finish is matt. Yellowing is a phenomenon that appears tem­ porarily as a result of the curing process and is particularly noticeable on l i ght-coloured surfac­ es. However, after a few hours in the daylight this discoloration d isappears.

d

e

C 6. 1 4

Floors

Laying Linoleum must be allowed to reach room tem­ perature prior to processing because it shrinks in the length and expands in the width. It must be laid on a dry, flat substrate, e . g . particle­ board, plywood , screed, concrete. Owing to the possibility of rotting on the underside, water must be prevented from seeping through the joints. Concrete floors in contact with the soil require a damp-proof membrane. Any significant une­ venness in the screed should be made good to ensure that the linoleum does not crack. U ne­ venness in the substrate is particularly noticea­ ble on plain coverings when viewed against the light, which is why the whole surface shou ld be filled prior to laying the linoleum. However, thicker types of l i noleum can compensate for small discrepancies in the substrate. If a jute textile backing absorbs water and expands before the adhesive dries, the linoleum may bulge at the joints. Surface treatment Patterned and plain linoleum floor coverings are normally coated by the manufacturer with a protective matt film, usually an acrylic disper­ sion. As this protective film partly seals the sur­ face, l i noleum is easy to clean. Linoleum manu­ facturers therefore recommend no special measures or cleaning agents for their products. Applications Linoleum can be laid in virtually all i nternal areas and owing to its antibacterial properties is particularly suitable for heavily trafficked sur­ faces in, for example, hospitals, schools and sports facilities. However, linoleum is not rec­ ommended for wet interior areas. Linoleum is easy to keep free from d ust and is therefore from the medical viewpoint - recommended for asthma sufferers (fig . C 6. 1 4 a) . Cork linoleum This floor covering exhi bits similar properties to standard linoleum. The addition of coarse cork powder to the l i noleum mass improves the elasticity and the impact sound insulation, and it also feels warmer underfoot. PVC

PVC floor coverings consist of a homogeneous layer of polyvinyl chloride to which diverse sub­ stances are added (including plasticisers and fillers such as chalk) to achieve specific prop­ erties (fig. C 6. 1 4 d) . The resulting floor cover­ ing is resistant to chemicals and ageing , is non-slip, hardwearing and i nexpensive. PVC flooring is easy to work and if the joints are welded together can even be used to create a watertight surface finish. The electrostatic behaviour ranges from insulatin g to antistatic to electrically conductive depending on the prop­ erties of product and adhesive. This easy-care floor covering is also suitable for more stringent hygiene conditions, e . g . hospi­ tals. Owing to their thermoplastic nature, PVC

floor coverings can be damaged by cigarette burns. And in a fire, PVC gives off hydrochloric acid, which corrodes concrete and steel and releases toxic fumes (CO, d ioxins, PAH) . PVC products belong to building materials class 8 1 (not read ily flammable) . After shredding and preparatory treatment, old PVC floor coverings can be reused in new flooring materials (max. 70% ) , but in practice the amount of material recycled is currently very low. PVC floor cover­ ings are just 1 .0-2 .5 mm thick. Although PVC floor coverings have undergone d i stinct improvements, they are still not without their critics. One non-hazardous p lasticiser that can be used is epoxidised soya oil. The materi­ al's life cycle assessment benefits from the low cleaning requirements and the good durabil ity. Design options PVC floor coverings can be manufactured to imitate certain other materials such as natural stone, ceramics, metals, etc. Countless pat­ terns, colours and textures are available. The design options would seem to be limitless, with new finishes being added all the time. Surfaces with three-dimensional effects are among the latest developments in the PVC flooring market. CV flooring This is a foamed floor covering with a softer layer of PVC beneath the wearing layer (CV = cushioned vinyl) . Such floor coverings exhibit better impact sound i nsulation values. C 6.16 Polyolefins

The search for a substitute for PVC floor cover­ ings resulted in the appearance of polyethyl­ ene, polybutene and polypropylene flooring products in the early 1 990s. These floor cover­ ings can be laid with water-sol u ble adhesives and require no plasticisers. They have simi lar properties to PVC products and can therefore be regarded as viable alternatives (fig . C 6 . 1 4 e). Although their life cycle assess­ ments are better, their market shares are cur­ rently sti l l smal l . Seams in resilient floor coverings

For reasons of hygiene and to enhance the appearance, also to cope with chair castors, joints in resilient floor coverings are often weld­ ed (PVC with a PVC cord, special jointing mate­ rials for linoleum and polyolefins) .

C 6. 1 3 Laminated flooring C 6. 1 4 Resilient floor coverings a linoleum b cork c rubber d PVC e polyolefin C 6 . 1 5 Interactive illuminated floor C 6 . 1 6 Thermosensitive polyester floor covering C 6. 1 7 Linoleum as wall and floor finish, boutique, New York, USA, 2000, Choi-Campagna Design

Outlook

Floor coverings are constantly undergoing developments to optimise their comfort, clean­ ing characteristics and wearing q ualities even further. Two examples serve to illustrate the progress in this field : SAF (=shock-absorbing foam) SAF is the designation for a highly elastic poly­ ester foam. Originally developed for medical purposes, fig. C 6. 1 6 shows the material in use as a floor coverin g . In this case a 25 mm layer of SAF is attached to an underlay of 1 00 mm C 6. 1 7

1 81

Floors

thick polyurethane foam. The depth of the imprint upon loading is influenced by the inten­ sity of the contact and the temperature. A per­ son leaves a trail of footprints until the material has fully recovered . Interactive illuminated floors An interactive illuminated floor is a type of sandwich panel. The uppermost layer is made from an elastic synthetic material, an opaque fluid forms the core, and the backin g layer is glass. A light source underneath can be seen when walking across the floor because the fluid is displaced, which allows the l ight to shine through. The footprints remain visible until the floor covering returns to its original state (fig. C 6. 1 5) .

Textile floor coverings

Rugs and carpets were orig inally hand-made luxury objects designed exclusively for deco­ rating prestigious interiors - on the walls as wel l . Mass production of carpets began in the 1 8th century, a development that triggered a new fashion in England: rooms were no longer decorated with wal lpaper, but instead with heavily patterned carpets. The 1 9th century saw the start of the industrial production of wall-to-wall carpeting, which in the second half of the 20th century underwent considerable developments thanks to the introduction of syn­ thetic fibres. Today, the range of industrially manufactured textile floor coverings encompasses natural fibres, synthetic fibres and blends of d ifferent fibres. A textile floor covering is a product with a wearing layer of textile fibre materials suitable for covering a floor. The wearing layer is called the p i le. The qual ity of a textile floor covering is essentially defined by the material, q uantity and processing of the pile threads. Good impact sound insulation and sound atten­ uation properties plus comfort and a feeling of warmth underfoot characterise textile floor cov­ erings. On the other hand , they are easily soiled and stains caused by fluids (e. g . wine, oil) require time-consuming cleani n g . A huge range of textile floor coverings is on offer in d if­ ferent qual ities and price categories to suit d if­ ferent wearing conditions. Colour, pattern and texture amplify this d iversity to form an almost infinite variety. Properties Textile floor coverings are tested by the manu­ facturers to D I N EN 1 307. This standard speci­ fies weight, beating-up, thickness of wearing layer, fibre material , behaviour in use and phys­ ical parameters, and provides details regarding suitability for potential applications. D I N EN 1 307 d istinguishes textile floor cover­ i ngs accord ing to four contract ratings: 1 low, 2 norma l , 3 heavy, 4 extreme. Owing to their vulnerability to soiling and the ensuing, limited service life, textile floor cover=

=

1 82

=

=

VllVV VllV a

c

b

d

ings are not recommended for heavily traf­ ficked entrance zones. The useful l ife of a tex­ tile floor covering depends heavily on the so­ called surface pile density. This is a theoretical value: weight of pile divided by thickness of pile. The higher this value, the higher is the density in the wearing layer of the floor cover­ ing. Comfort is covered i n D I N EN 1 307 by allocat­ ing textile floor coverings to so-called comfort classes LC 1 -5. Walking across a textile floor covering can lead to electrostatic charges building up. The electrostatic properties can be improved with a chemical coatin g , or - a more durable solution - by weaving in stainless steel or copper threads, or yarns with a carbon con­ tent. Textile floor coverings belong , in principle, to building materials class B 2 (flammable). How­ ever, testing can result in a further d ifferentia­ tion i nto classes T-a, T-b and T-c. Class T-a is the best and corresponds to building materials class B1 (not readily flammable) , whereas T-c is approximately class B3 (highly flammable) . Further suitabil ity recommendations ease the choice of the optimum product. For instance, details regard ing light-fastness, suitability for wet interior areas, chair castors and staircases are all common.

fibres of which point upwards. In a velour the threads of the yarn are cut, and the surface consists of these cut ends (figs C 6. 1 8 c and C 6. 1 9 c) ( cut-pile carpet). I n looped-pile carpets (boucle) the ends are not cut (figs C 6. 1 8 d and C 6. 1 9 b) . Needle-punch floor coverings have a wearing layer of a consolidated fleece consisting of fibres (fig . C 6. 1 8 b). Natural fibres such as jute cloth or synthetic fleeces can be used as the backing material for the pile.

Structure Textile floor coverings are deSignated accord­ ing to their basic material but also accord ing to their structure and backing. We d istinguish between flatweave and pile carpets (fleece, velour and boucle) . Flatweave carpets Flatweave carpets are produced on weaving looms (figs C 6. 1 8 a and C 6 . 1 9 a). Warp and weft threads form a relatively thin wearing layer; a further layer (backing) can enhance the com­ fort. The most common materials used are natural plant fi bres such as coconut, sisal and jute. Pile carpets The wearing layer i n a pile carpet is formed by the pile. Woven into a backing material, the pile forms a dense, resilient layer of thread, the

C 6. 1 8

=

Backing material Foamed coatings, synthetic fleeces, poly­ urethane or latex coatings and jute cloth can be considered as backing materials. In velour products the backing material also provides the fixing for the threads of the pile. Fleece backings improve the comfort underfoot, but soft foams are not suitable for chair castors. Products with a so-called secondary, textile backing are often recommended for office bui ldings. These floor coverings can also be completely removed from the substrate even if they were originally g lued down, whereas foam backings often leave a residue behind which must be removed - a time-consuming opera­ tion. Production Woven carpets req u i re three groups of threads parallel with and two transverse to the d i rection of production. The stitching warp pulls the lon­ gitudinal pile threads onto the two transverse wefts above and below the longitudinal filling warp. The weaving is assisted mechanically by the so-called round wires. If these are blunt, the loop of the pile is retained, and boucle (Iooped­ pile) goods are the result. Blades on the round wires produce velour (cut-pile) goods. The tufting method sews the loops to a backing material to create loops on the underside. Only a coating on the underside g uarantees a per­ manent attachment. Looped-pile carpets con­ sist of one continuous thread. If the loops are cut, the result is a cut-pile carpet, similar to velour. One great advantage of this method is the speed of production, which is up to 20 times faster and hence less costly.

Floors

The needle-punch method joins and compacts loose fleece plies with the help of needles to form a very hardwearing floor covering. Nee­ dles fitted to beams punch through the pre­ pared fleece at high speed , barbs cross the fleece layers with one another and with the backing material. An impregnation treatment seals the fibre composite. Kugelgarn® consists of countless fibre spheres that form a three-dimensional and very robust wearing layer (fig. C 6 . 1 9 f) . Other methods such a s knittin g , flock coating , pressing, bonding, etc. are not covered here. Laying Most carpets are g lued to the substrate over their full area. The residual moisture content of concretes or screeds must be tested before­ hand. Floor coverings with a foam backing can­ not be detached from the substrate without ruining the covering completely. New types of adhesive are being developed that wi l l adhere to the carpeting and ease replacement.

Laying loose Smaller areas can also be laid loose or secured with double-sided adhesive tape. However, general usage as wel l as temperature and moisture fluctuations can easily lead to bulges. Carpet tiles are suitable for contract carpetin g , especially in conjunction with raised floors. Their heavyweight backing material enables them to be laid loose and so the accessibil ity of the raised floor is thus retained . Laying with gripper strips It is possible to attach carpets to strips of steel hooks. These so-called gripper strips are fixed to a stable substrate adjacent to the walls and the carpet is stretched tightly between them. Carpets for this type of laying should have a stable secondary, textile backin g . An approx. 6 mm thick fleece can be used as an underlay. This type of floor covering is not suitable for . use in conjunction with underfloor heating because the fleece underlay functions as ther­ mal insulation. Laying with gripper strips makes replacement at a later date much easier, and the comfort and lifetime of the carpet are con­ siderably improved (up to 50% longer life) . This is an environmentally friendly technique because both fixings and fleece underlay can be reused. Cleaning and care Carpets can be cleaned with brushes and vac­ uum cleaners. The more intensive special cleaning measures include foam treatments and cleaning by special companies. Whether soiling is readily or less readily noticeable depends on colour, colour intensity and pat­ tern. Fibre materials and structure also have an influence on the frequency of clean i n g . People with house dust allergies are generally advised to avoid textile floor coverings.

Natural fibres

Natural fibre carpets are divided into those based on vegetable materials and those based on animal materials. It is generally true for all natural fibre floor coverings that as the comfort increases, so the wearing q ualities decrease. In addition, the carpets offering better comfort are less hardwearing than comparable carpets made from synthetic fibres. This is probably the cause of their low market share. Natural fibre products are frequently g iven a chemical surface coating to help conserve the fibres, to optimise the soiling behaviour and to protect against moths and other vermi n . The coating adheres to the fibres but wears off d uring use.

C 6. 1 8 Types of carpet a flatweave b fleece c velour d looped pile C 6. 1 9 Textile floor coverings a flatweave b looped-pile carpet (boucle) c velour d wool carpet e sisal f Kugelgarn®

Vegetable fibres Carpets made from vegetable fibres such as hemp, sisal, coconut and jute are mainly avail­ able in the form of flatweave goods (fig. C 6.1 ge). On the other hand, cotton fibres can also be used as a pile material, which in contrast to other floor coverings is not elastic, but has a p leasant feel. These carpets are hardwearing and available without moth protection. Animal fibres Carpets made from animal products such as hair and silk are mentioned here for the sake of completeness. Animal hair such as wool, camel hair, etc. have a very good sorption capacity. Additions to the wool , e . g . goat hair, improve the wearing qualities of the floor covering. Wool Wool carpets are available i n two qualities: new wool is obtained by from sheep by sheari n g , b u t recycled or reprocessed wool c a n also b e used. New wool products exhi b it high elasticity, are not susceptible to soiling and are not readi­ ly flammable. The high moisture absorption capacity of wool has a beneficial effect on the interior climate. Blending with synthetic fibres improves the wearing q ualities of wool carpets (fig . C 6. 1 9 d) . The "Wool mark" is an interna­ tional symbol of q uality which g uarantees that the wearing layer is made from 1 00% new wool . Synthetic fibres

Synthetic fibres are man-made goods pro­ d uced from crude oil products. As a rule, they cannot absorb any moisture. The advantage of this is that they are resistant to staining by drinks and simi lar fluids. I n itially smooth fibres can be mechanically prepared to improve the feel and the resistance to soil i n g . Coatings can improve the electrostatic properties and the soiling behaviour, or are i ntended to protect the material against fad i n g .

d

Polyamide fibres (PA) The most common fibres exhibit a high wearing resistance, minimal soi l i ng vulnerabil ity and a good regeneration capacity. They can be u pgraded to antistatic floor coverings by add­ ing carbon to the fibres. Owing to their good C 6. 1 9

1 83

Floors

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Floor covering

Normal Normal thickmethod ness of fixing

Density

[mm]

[kg/m"]

Weight

Thermal conductivity

Water vapour diffusion resistance

[kg/m>]

[W/mK]

H

Building materials class/ combustibility class

Contract ratings available

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Stone granite marble travetine slate reconstituted stone

1 0- 30 1 0-30 1 0- 30 1 0-15 1 2 -50

mortar, thin-bed mortar 2600-2800 2600-2900 2400-2500 2700-2800 2200-2400

26-84 26-87 24-75 27-36 26-120

2.8 3.5 2.3 2.2 1 .6 - 2 . 1

1 0 000 1 0000 200/250 800/1 000 70/150

A 1 /A" A 1 /A" A 1 /A" A1/A" A 1 /A"

D I N EN 1 4 1 57 pt 1 -4 (for nalural stone tiles < 1 2 mm thick)

Ceramics stoneware tiles earthenware tiles split-face blocks engineering bricks

7-1 5 5-9 8-1 1 1 0-40

mortar, thin-bed mortar 2000-2400 2000 2000-2400 vibratory compaction, 2000-2200 elutriation

1 4-36 1 0- 1 8 1 6-26 20-88

1 .0 1 .0 1 .0-1 .05 0.96 - 1 .2

1 00/500 ' 1 00/500 ' 1 00/500 ' 1 50'

A1/A" A1IA" A1/A" A 1 /A"

D I N 1 4 4 1 1 pt 1 -5 glazed tiles

nailed, floati ng nailed, glued glued glued glued, floating glued, floating

430-760 430-760 430-760 430-760 740 800

6-30 6-1 7.5 3.5-7.5 4-1 7 5-19 6-9

0.09-0. 2 1 0.09-0. 2 1 0.09-0. 2 1 0.09-0.21 0. 1 5 0. 1 7

40 40 40 40 50/400 1 000/2500 4

up to 8 1 / 8,, -s1 l0 E" up to 8 1 / 8,,- s 1 l0 E" up to 8 1 / 8,, -s 1 to E" up to 8 1 / 8,,-s1 l0 E" up to 81/8,,-s1l0 E" u p to 8 1 / 8,, -s1 l0 E"

not std . ; differs considerably dependin9 on species of wood ·

2-6 2-5 2-5 2-3 2-3

glued, floating full/partial gluing full/partial gluing full/partial gluing full/partial gluing

400- 500 1 200 1 000-1 200 1 700 1 500-1 700

1 -3 2-6 2-6 3-5 3-5

0.065-0.07 20/40 0.1 7-0.64 1 0 000 0.08-0. 1 7 800/1 000 0 . 1 0-0.25 1 0 000 0.23-0.25 1 0 000

5-8 5-6

full/partial gluing between gripper strips

200 200

1 -2

0.06 0.54

0

Wood solid floorboards 1 5 -40 wood-block flooring 1 4 -22 mosaic parquet 8-10 block-on-edge parquet 1 0 -25 wood parquet laminate 7 - 26 laminated flooring 7-1 1

0 0 0 0

0 0

D I N EN 1 4354; 2 1 -23, 31 -33 DIN E N 1 3329; 2 1 -23, 31 -33

.3

.3

0

Resilient floor coverings cork rubber linoleum PVC polyolefins

up to 8 1 / 8,, -s1 l0 E" D I N EN 685; 21 -23, 3 1 -34, 8 1 / 8,, -s1 to C,,-s1 4 1 - 43 up to 81/C,,-s1 to E" up to 8 1 / 8,,-s1 to E" up to 81/8,,-s1 to E"

0

0 0

.3

0

0

.3

0

02

.3

0

02

.3 .3

Textile floor coverings carpeting needle-punch fleece

5 5

up to 81/8,,-s1 to E" DIN EN 1 307 1 , up to 81/8,, -s1 to E" 2, 2+, 3, 4

0 0

0

' These values apply to ceramics in situ; individual values, e.g. stoneware tiles 1 2 000; earthenware tiles 1 0 000. With backing 3 When used in conjunction with underfloor heating, a full bond with the substrate is essential. 4 Values apply to a single panel of laminated flooring without joints. 2

wearing q ualities, polyamide fibres are used for the so-cal led walk-off mats and carpets manu­ factured for entrance zones.

before spinning to form a yarn. Dying can take place at any stage of the carpet manufacture. Blends

Polyacrylonitrile fibres (PAN) These fibres have a similar feel to wool , but are more hardwearing. Polyester fibres (PES) Besides their high wearing resistance, polyes­ ter fibres have a gloss surface. They absorb only very l ittle moisture. Polypropylene fibres (PP) Polypropylene fibres repel moisture and are not affected by ultraviolet radiation, and therefore can be used externally and in wet interior areas. The regeneration capacity is low, which means that these fibres are preferably used in the form of fleeces.

C 6.20 C 6.20 Parameters of floor coverings C 6.21 "Shining Islands", polyamide carpeting with fluorescent coating, furniture trade fair, Cologne, Germany, 2002, Nether C 6.22 Life cycle assessment data for floor coverings

Basically, all types of yarn can be used in any combination for the production of a carpet. As the properties vary in proportion to the ratio of the d ifferent fibres, it is easy to reach an opti­ mum performance. Depending on the intended range of applications, it is possible to combine, for example, natural fibres with more hardwear­ ing synthetic fibres, or for synthetic fibres to achieve a more pleasant feel by incorporating natural fibres. Outlook

The use of certain coloured coatings and struc­ tural measures can enable textile floor cover­ ings to generate a three-dimensional impres­ sion. Fig. C 6.21 shows an example of synthetic fibres with fluorescent properties.

Yarn manufacture A melt of the corresponding plastic granulate is forced through a die (spinnerette) at high pres­ sure, and the length of the fibres increased by drawing. The fibres are initially too smooth for processing. They are therefore given a texture C 6.21

1 84

Floors

EP eutrophication [kg PO.eq]

Durability POCP summer smog [kg C2H. eq] [a]

0.0050

0.00041

0.0010

70- 1 00

0.0 1 5

0.00 1 6

0.0020

70- 1 00

0

0

0.043

0.0051

0.052

40-80

0

c::::J

c:::=J

0.053

0.0044

0.0080

40-80

c:::J

c:::J

0.026

0.0030

0. 1 4

20-50

0

0

0.041

0.0035

0.0050

20-50

0

0

0.033

0.0036

0.10

20-50

0

0

�

0.033

0.0033

0.057

0

D

c::J

0.037

0.0028

0.0050

10-15

D

0

0.01 1

0.00 1 4

0.0020

1 5-40

0.078

1 5-40

PEI primary energy non-renewable [MJ]

PEI primary energy renewable [MJ]

AP GWP ODP global acidifiozone cation depletion warming [kg C02 eq] [kg R 1 1 eq] [kg S02 eq]

16

0.7

1 .0

0

slate'

43

1 .1

3.5

0

slate flags, 300 x 300 mm, MG I I I mortar joints, 20 mm MG 11 mortar bed, 1 2 mm

•

Floor coverings Layers • for origin of data see "Life cycle assessments", p. 1 00

Natural stone limestone' limestone flags, 305 x 305 mm, MG I I I mortar joints, 1 0 mm thin-bed mortar, 3 mm

0

Ceramics terracotta

1 37

terrac. tiles, oiled, 300 x 300 mm, MG I I I mortar joints, 1 5 mm MG 11 mortar bed, 1 2 mm

-

glazed ceramic tiles'

1 62

glazed tiles, 1 00 x 200 mm, MG I I I mortar joints, 8 mm thin-bed mortar, 3 mm

-

14

3.2

0

�

5.1

5.3

0

=

Solid timber and wood-based products wood-block flooring

66

wood-block flooring, beech, oiled, 22 mm alkyd resin adhesive

-

mosaic parquet

79

mosaic parquet, oak, sealed, 8 mm alkyd resin adhesive

-

wooden floorboards

84

floorboards, larch, oiled, nailed, 1 9.5 mm battens, 80 x 80 mm granulated cork fill, 50 mm

-

real wood parquet laminate flooring

74

real wood parquet laminate flooring, beech, 15 mm polyurethane adhesive laminated flooring laminated flooring with melamine resin coating, 8 mm polyurethane adhesive polyethylene fleece (PE)

447

1 74 �

487

31 1

-42

-13

0

0

c:::===J -44

-27

0

0

91

-

54 CJ

-2.6

0

0

20-50

Resilient floor coverings linoleum

24

linoleum (roll), 2.5 mm polyvinyl acetate (PVAC) adhesive

•

rubber

702

29

-0.4

0

0

15

0

21

0

0. 1 9

rubber (roll) without inlay, synthetic, 4.5 mm polyurethane adhesive

0.Q1 6 I j

cork, waxed

22

cork tiles, waxed, 6 mm latex adhesive

•

PVC

1 18

PVC (roll), 2 mm polyvinyl acetate (PVAC) adhesive

-

54 CJ

23 0

-5.2

0

0

=

1 5-40

0.0022

0. 1 1

0

c:::::::=:::J

0.066

0.0059

0.0070

1 5 -30

c:=J

c:::=J

0.047

0.0038

0. 1 0

5- 1 5

=

=

�

0.Q1 1

0.00081

0.082

0.0 1 0

= g.g

I c::=::J

Textile floor coverings carpet, natural sisal

1 64

carpet, natural sisal, natural latex backing, 6 mm alkyd resin adhesive

-

carpet, new wool

39

carpet, new wool , looped-pile, 6 mm jute felt polyvinyl acetate (PVAC) adhesive

•

carpet, fully synthetic

225

carpet, cut-pile, foam backing, 7 mm polyvinyl acetate (PVAC) adhesive

33 0

27

3.3

0

0

-1 . 1

0

c::=:J

0

5.2

5- 1 2

7.3

=

0

0.079

0.0077

0.027

c::=:J

C=:J

0

5- 1 2

C 6.22

1 85

Surfaces and coatings

As the boundary between materials and the environment, surfaces stimulate the senses, I ni­ tially, it is the visual impression of a surface that dominates, This depends on the nature of the surface, which may be, for example, smooth, shiny, rough, wavy or decorated, An object or a b u i l d i n g can appear in any gradation from heavyweight to transparent d ue to the incident light, colours and reflections, Additional haptic, acoustic, sometimes even olfactory, sensual perceptions triggered by a material have an influence on the quality of an object beyond its mere constructional and functional uses,

I n ancient Egypt and later in Greece, the sym­ bolic use of colour played a role in sculptures and architecture, In ancient Rome plaster or stucco reliefs imitated marble and clay clad­ d i n g , And the i nteraction between architecture, painting , sculpture and ornamentation was deliberately sought d uring the Baroque era, Classicism, the antithesis of late Baroque and Rococo, looked back to the ancients, During these periods the "white architecture of the ancient times" was the ideolog ical motivation, White was a metaphor for honesty and purity in architecture,

The surfaces of the building envelope are exposed to severe stresses and strains, C l i mat­ ic and environmental influences alter the sur­ faces over the course of time just as much as the traces of everyday use, Some materials possess an ageing q uality and acqu i re a pati­ na, but others require regular renewal or care to prevent decay, If the materials used to not resist ageing or do not form a patina, their durabi l ity and hence the retention of their mate­ rial value depends on the maintenance cycles of the coatings intended to protect them, Coat­ ings are invisible means of prolonging the l ife­ time or modifying the properties of materials, They refine the substrate by highlighting the typical features of the material or by provid i n g a f u l l protective coveri n g ,

During the 1 920s and 1 930s pure white coat­ ings were regarded as the ideal surface finish, the aim of which was to prevent diverting atten­ tion from the architectural and constructional concepts, During the same period , Bruno Taut used colour as an inexpensive architectural medium. By al locating this medium a symbolic and emotional meaning, he brought about a new social identification with the building, And Le Corbusier, talking of colour, said : "Colour as a means in architecture is just as powerful as the p lan layout and the profile. Or put a better way: polychromy is a constituent of the plan layout and the profile itself."

Liq uid or paste-like coating materials, plasters and renders are applied in one or more coats and form a protective system compatible with the substrate, Pigments and fillers made from stone dust can be mixed in to add colour to the surface, Although coatings account for only a small fraction of the cost of erectin g a structure, the appearance of the surface has a crucial effect on the architecture,

Colour

The word colour has several meanings and is used by the layman and expert alike to describe different aspects, which can lead to many misunderstandings. D I N 5033 defines colour as a sensation; it is therefore not a phys­ ical property of an object. Referring to paints and other coating materials simply as "colours" should therefore be avoided. Perception of colour

C 7,1 C 7,2 C 7,3 C 7,4

White l i g ht is the electromagnetic radiation with wavelengths between 380 and 780 nm. It was in 1 705 that Isaac Newton first split white light systematically into its constituent wavelengths the spectrum - with the help of a g lass prism, The spectrum consists of the monochromatic spectral colours violet, indigo, blue, green, yel­ low, orange and red . Both ends of the spec­ trum exhibit visual similarities, and joining the ends together forms a colour wheel. All the other colours are formed by mixing together the colours of the spectrum, e . g . magenta is formed by blending red , orange, violet and blue. Only when the beams of light enter the human eye and trigger a colour stimulus in the brain can the observer describe a colour and place it in relation to other colours. Our perception of colour is determined by its two fundamental forms: self-luminous colours generate the colour stimulus when the coloured light from a source of radiation enters the eye d i rectly or through a filter, whereas object col­ ours generate the colour stimulus when a part of the light is reflected from the surface of an object before striking the retina. An object that

Satellite City Towers, Mexico City, Mexico, 1 957, Luis Barragan NCS colour solid with colour triangle NCS colour wheel Monastery of La Tourette, Eveux-sur-Arbresle, France, 1 960, Le Corbusier C 7.1

1 86

Surfaces and coatings

� y

absorbs all the light incident upon it appears black. Object colours are always perceived in relation to other colours and also depend on the colour of the incident l i g ht.

15

;:

is

� I ...

$'

. "" ""��

..,of'