THE ECOLOGY OF BUILDING MATERIALS

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THE ECOLOGY OF BUILDING MATERIALS

Bjørn Berge Second edition Translated by Chris Butters and Filip Henley

AMSTERDAM • BOSTON • HEIDELBERG • LONDON • NEW YORK • OXFORD PARIS • SAN DIEGO • SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO

Architectural Press is an imprint of Elsevier Linacre House, Jordan Hill, Oxford OX2 8DP, UK 30 Corporate Drive, Suite 400, Burlington, MA 01803, USA First edition 2000 Reprinted 2001 Second edition 2009 Copyright © 2009. Elsevier Ltd. All rights reserved. The right of Bjørn Berge to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988 No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher Permissions may be sought directly from Elsevier’s Science & Technology Rights Department in Oxford, UK: phone (+44) (0) 1865 843830; fax (+44) (0) 1865 853333; e-mail: [email protected]. Alternatively you can submit your request online by visiting the Elsevier web site at http://elsevier.com/locate/permissions, and selecting Obtaining Permissions to use Elservier material Notice No responsibility is assumed by the publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloguing in Publication Data A catalogue record for this book is available from the Library of Congress ISBN: 978-1-85617-537-1

For information on all Architectural Press publications visit our web site at www.Elsevierdirect.com

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09 10 11 12 13

10 9 8 7 6 5 4 3 2 1

To Dag Roalkvam, my enthusiastic and wise colleague through three decenniums

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CONTENTS

Foreword to the Second Edition Introduction The ecology of building materials How to use this book Other guidelines for reading this book Part 1

Environmental profiles and criteria for assessment

xii xiii xv xv xviii 1

1 Resources Material resources Actions for resource conservation in the production of materials Reduction of the use of materials in the building Raw materials in a world context Energy resources Stages of energy consumption in building materials Reduction of energy consumption in the building industry References

3 6 6 8 18 19 19 21 27

2 Pollution Energy pollution Material pollution Global warming Climate emissions from the building sector Carbon processes in building materials Other pollutants Environmental poisons Substances that reduce the ozone layer Acid substances Formation of photochemical oxidants (low ozone) Eutrophicating substances Particles Genetic pollution Nanoparticles Reduction of pollution in the production of materials Reduction of pollution in construction, use and demolition References

29 29 30 31 32 34 35 35 36 36 40 40 41 41 41 42 43 47

3 Local production and the human ecological aspect The quality of work Technology Economy and efficiency Reconnecting to the natural systems References

49 51 52 53 55 55

4 The chemical and physical properties of building materials An introduction to the chemistry of building materials Radioactivity Weights of the substances in a chemical reaction Supply and release of energy in chemical reactions

57 58 58 59 60

viii Contents

Part 2

Other conditions for chemical processes The elements Important factors in the physics of building materials References

61 61 62 63

Further reading for part one

64

Raw materials and basic materials

65

5 Water and air Water Ice and snow Air

67 67 68 69

6 Minerals Metallic minerals Raw materials Recycling Metals in building Iron and steel Aluminium Copper Zinc Secondary building metals Non-metallic minerals The most important non-metallic mineral raw materials for the building industry Non-metallic mineral basic materials in building Cements and limes Glass References

71 71 75 75 76 76 78 80 80 80 82 86 91 91 99 104

7 Stone Production of building stone Extraction methods Dividing and cutting blocks Sorting and cutting slate Crushed stone or stone block? References

107 110 111 113 115 116 116

8 Soil materials Soil materials in building Sand and gravel as aggregate in cement products Earth as a building material Finding and extracting raw materials Deciding technical properties Moisture and shrinkage The preparation of earth Earth structures Brick and other fired clay products Brick manufacture Manufacture of ceramic tiles Production of light expanded clay Fired clay products and reduced energy consumption References

119 120 122 123 125 126 127 128 128 128 129 134 135 136 138

9 Fossil oils The basic materials Bitumen and tar Solvents and other chemicals Plastics in building Pollution related to the most important building plastics Durability of plastic products Recycling References

139 142 142 142 146 148 153 155 156

Contents ix

Part 3

10 Plants Living plants Turf Climbing plants and hedges Timber Forestry The durability of timber Recycling Grasses and other small plants Cultivating and harvesting Preparation Building chemicals from plants Cellulose References

157 163 163 164 165 168 172 173 174 176 176 177 178 179

11 Materials of animal origin References

181 183

12 Industrial by-products Industrial gypsum Sulphur Silicate dust Blast furnace slag Fly ash Fossil meal Fibrous cellulose sludge References

185 185 185 186 186 187 187 187 187

Further reading for part two

188

Building materials

189

13 Structural materials Metal structures Concrete structures The composition of concrete The durability of concrete products Recycling Stone structures Structural elements Structural brickwork Brick products Recycling Earth structures Suitable types of earth Stabilizing aggregate and other additives Methods of construction Timber structures Structural elements in timber The use of timber in building Turf constructions Resource use and climate load of different structural systems References

191 193 194 195 200 201 201 202 204 206 206 208 209 209 210 216 217 219 232 233 237

14 Climatic materials Temperature regulating materials Air regulating materials Moisture regulating materials Noise regulation Snow as a climatic material Metal-based materials Materials based on non-metallic minerals Cement products Gypsum products Fossil meal products

239 240 243 245 251 252 252 254 256 257 258

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Contents Perlite and pumice products Vermiculite products Silica aerogel Foamglass Mineral wool Montmorillonite Fired clay materials Earth and sand as climatic materials Bitumen based materials Plastic materials Environmental aspects Timber materials Sawdust and wood shavings Bark Woodwool cement Defibrated wood fibre Wood fibre matting Porous wood fibre boards Moss and grass materials Grass plants Moss Bog peat Cellulose Materials based on animal products Materials based on recycled textiles References

259 259 260 260 261 262 262 264 268 269 270 272 274 276 277 278 279 279 281 282 286 287 289 290 291 297

15 Surface materials Metal surface materials Non-metallic mineral surface materials Roofing Sheets for cladding Plaster Flooring Stone surface materials Fired clay Surfaces of earth Bitumen-based materials Plastic surface materials Living plant surfaces Planted roofs Wall cladding with plants Indoor plants Timber sheet materials Roof covering Timber cladding Wooden floors Natural rubber (latex) Wood-based boards Grass materials Roofing and wall cladding with grasses Grass boarding Soft floor covering of linoleum Boarding from domestic waste Carpets and textiles Wallpapers References

299 302 303 304 305 307 309 310 313 315 316 317 319 320 324 325 325 328 332 335 338 338 340 341 343 345 346 346 348 355

16 Windows, doors and stairs Windows and doors Glass and methods of installation Timber windows Timber doors Plastic and aluminium windows and doors Stairs References

357 357 358 361 362 364 365 367

Contents xi 17 Fixings and connections Mechanical fixings Timber Metal Chemical binders Mortars Adhesives and fillers References

369 369 370 371 372 372 373 380

18 Paint, varnish, stain and wax Conditions for painting The main ingredients of paint Binders Solvents Pigments Other additives Paints with mineral binders Lime paint Silicate paints Cement paints Paints with organic binders Synthetic paints and varnish Animal glue paint Vegetable oils Tar Natural resins Starch paint Cellulose products Stains Beeswax Green soap References

381 388 388 388 388 389 392 393 394 396 396 396 396 398 400 402 402 403 403 404 406 406 407

19 Impregnating agents, and how to avoid them Choosing high quality material Structural protection of exposed components Methods of passive impregnation Methods of active impregnation References

409 410 411 412 415 418

Further reading for part three

419

Index

421

Foreword to the Second Edition

The Ecology of Building Materials was originally published in Norwegian in 1992, and the first English edition appeared in 2000. The book you have before you now represents a comprehensive revision; it has been updated in the light of new materials, knowledge and practical experience accumulated during the past decade. If the quantity of information produced during these years is anything to go by, environmental questions have never been higher on the international agenda. The issue of climate change has played a central role, with successive and increasingly alarming reports from the International Panel on Climate Change (IPCC). Whilst keeping to the same basic structure, the book has been considerably expanded. In particular this applies to climate related issues. The wealth of information now available has also made it possible to raise the general level of precision in many areas. As with the previous edition, it is still the basic intention that this book shall serve as a reference book, rather than being read from cover to cover. Some overlapping and repetition has therefore been necessary. Whilst Filip Henley translated the first edition, the translation of this edition has been undertaken by my colleague in Gaia Oslo, Chris Butters, whose knowledge and experience in the field of building ecology is exceptionally broad. He has also contributed with suggestions and additions that are integrated into the present text. My colleague Dag Roalkvam, also in Gaia Lista, has contributed similarly within the field of building physics where he is a recognised expert; and Rolf Jacobsen of Gaia Tjøme in the field of construction in straw and earth, one of his specialities. I also wish to renew my thanks to others who have contributed to earlier editions of this work, including Frederica Miller, Howard Liddell, Varis Bokalders, Jørn Siljeholm, Hans Granum, Arne Næss, Karls Georg Høyer, Geir Flatabø, Per Richard Neeb, Odd Øvereng and Tom Heldal. In this new edition, illustrations have been substantially upgraded and have been provided from many sources; in particular I wish to thank Anne €m, Sigrid Nordby, Alice Reite, Rolf Jacobsen, Sergio G. Fox, Bertil Harstro Rod Ward Able, Dag Roalkvam, Camilla Høyem, Inga Lindstrøm and Anette Rosenberg. Bjørn Berge Lista, 2008

Introduction

We cannot cure illnesses, but we can help Nature cure herself. Hippocrates

I object! I do not agree that the Earth and everything that exists on her shall be defined by the law as man’s living environment. The Earth and all that is hers, is a special being which is older, larger and stronger than us. Let us therefore give her equal rights and write that down in the constitution and in all other laws that will come. . . A new legal and moral status is needed where Nature herself can veto us through her own delegates. . . One must constitute the right of all things to be themselves; to be an equal with Nature, that is totally unarmed; do well out of it in a human way and only in accordance with their own nature. This means that one must never use a tree as a gallows, even if both its form and material fit the purpose excellently. . . What practical consequences should a law like this have? Before all economic considerations, this law would decide that nothing will be destroyed or severely damaged, all outstanding natural forms, landscape characteristics and naturally linked areas shall remain untouched. No economic or leisure concern shall be developed at the cost of nature, or worsen the living conditions of man and other beings. Everything that man wants to do in the future, he must do at his own cost and with his own strength. As a result of this law we may return to old methods of production or discover new ones which do not violate the law. The manufacturing society will crumble and multiply, the meaningless superfluity of similar products on the world market will give way to the local market, independent of transcontinental connections. Ludvı`k Vaculı`k, Czech author, in his essay An alternative constitution

The Greek terms economy, ecology and ecosophy belong together: Oikos House Nomos Management Logos Understanding Sofos Wisdom If we consider the world to be our common house, we can say that we have managed too much and understood too little. In Nature – the existential base of humanity – the consequences of this are becoming clearer: melting of polar ice caps, desertification, diminishing biodiversity. These are things of which we are all aware. The growing incidence of stress and mental problems among the populations of industrialized nations would indicate that we have not even understood the nature of ourselves – that we, too, have become the victims of too much management.

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Ecosophy expands the Kantian imperative ‘to see every person as a goal, rather than a means’, and to include other living beings. In this way, it defends the value of Nature in itself, and acknowledges that it is impossible to escape the third law of ecology: ‘All things are connected’ (Commoner, 1972). We need a sustainable perspective of Nature that has a guiding influence on human activity or, alternatively, a general morality which is acceptable to all. The ecologist Aldo Leopold maintains: ‘A thing is right when it tends to preserve the integrity, stability and beauty of the biotic community. It is wrong when it tends otherwise.’ This represents an ethic for which, in ancient times, there was no need. Trond Berg Eriksen (1990) describes the situation in antiquity: In antiquity, commanding the forces of Nature and bringing discipline to human nature were two sides of the same coin. In neither area did the interveners need to fear that they would succeed completely. The power of Nature was overwhelming. It took care of itself. Humans had to battle to acquire the bare necessities. Nature’s order and equilibrium was unshakeable. Man was, and considered himself, a parasite on an eternal life system. The metropolis was a hard won corner, a fortified camp under threat from earthquakes, storms, drought and wild animals. The metropolis did not pose a threat to Nature, but was itself an exposed form of life... In such a perspective, technology was ethically neutral. Morality comes into play only when one can cause damage, in relation to someone or something that is weaker or equally strong. Therefore, the consequences of human actions for non-human objects lie beyond the horizon of moral issues.

Our ancestors’ morality was based on the axiom that people themselves were the only living beings that could be harmed by human actions. Ethics focused on this; and ethics dealt with interpersonal relationships. At the same time this morality was limited to the moment – only the immediate consequences of an action were of significance. Long-term effects were of no interest and beyond regulation. Today, humankind’s position and influence is drastically changed. The way in which we manage natural resources may have irremediable consequences for future generations of all life forms. Paradoxically, we still cling to antiquity’s anthropocentric moral philosophy, often mingled with some of the Enlightenment’s mottos of our sovereign supremacy. ‘Four conditions to achieve a sustainable society’, according to L.P. Hedeberg of the movement ‘The Natural Step’, are: 1. Do not take more out of the crust of the Earth than can be replaced. This means that we must almost totally stop mining and use of fossil fuels. Materials that we have extracted from beneath the Earth’s surface (for example, metals, coal and oil) are difficult for Nature to renew, except in very small quantities. And that takes time. On the surface the rubbish pile gets higher because we have not followed this condition. Matter does not disappear; even if we reduce it to fine particles (by combustion, for example); it is only transformed into molecular waste. Every atom of a completely rusted car continues to exist and has to find a new home somewhere else. Everything may spread, but nothing disappears. 2. Do not use man-made materials that take a long time to decompose. Materials that Nature can break down and change into nutrients belong to the natural lifecycle. Many man-made materials, which have

Introduction

never been a part of Nature, are very difficult for Nature to break down. Certain synthetic materials such as dioxins, DDT, fluorocarbons and chloroparaffins will almost never be broken down by Nature. 3. Maintain the conditions needed for Nature to keep its production and its diversity. We must stop impoverishing Nature through forest clearing, intensive fishing and the expansion of cities and road systems. The great diversity of animals and plants are a necessity for all life cycles and ecosystems, and even for our own lives. 4. Use resources efficiently and correctly – stop being wasteful. The resources that are available must be used efficiently and distributed fairly.

THE ECOLOGY OF BUILDING MATERIALS Is it realistic to imagine a technology that is in line with holistic thinking whilst also providing humanity with an acceptable material standard of living? This book illustrates the role and potential of building materials in such a perspective. And, in the same context, to illuminate the following aspects: *

*

*

*

Work. The methods used to produce each building component. How production takes place and can take place. Raw materials. Occurrence of material resources, their nature, distribution and potential for recycling. Energy. The energy consumed when producing and transporting the materials, and their durability. Pollution. Pollution during production, use and demolition, the chemical footprint of each different material.

A primary goal of this book is to enable the various actors in the building industry to pose environmental requirements, and to do this with greater precision. In order to ensure an environmentally responsible building, it is important to obtain precise answers to questions such as ‘Is the steel produced in a blast furnace or an electric arc furnace?’; ‘Are pozzolanas used in the cement clinker?’; or ‘What kind of adhesive is used in the hemp matting, and how much?’. It is also hoped that the book will contribute towards reducing misleading advertising information. Green products are now much in demand, and many producers are claiming to fit this mould without apparent justification.

HOW TO USE THIS BOOK The Ecology of Building Materials is an attempt to present the possibilities for existing materials, as well as evaluating new materials. A number of partly abandoned material alternatives have also been evaluated. In particular, we will look at vegetable products, often with traditional methods of preparation. In their present state these methods are often of less relevance, and these reviews must therefore be regarded as tentative. Many factors relating to the materials discussed depend upon local conditions; this book is primarily based on the climatic and topographical conditions in northern and central Europe. However, when

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considering the Earth as a whole, it will become clear how little the overall use of materials varies; and the principles underlying better solutions to a large extent are universal. The materials dealt with are those that are generally used by conventional builders such as bricklayers, masons, carpenters and locksmiths. Under this category, all fixed components and elements that form a building are included, with the exception of heating, ventilation and sanitary installations. Materials providing high environmental standards are presented most thoroughly, whilst less attractive and often conventional alternatives are given less attention. The book is divided into three Parts: Part 1: Eddies and water-level markers. Environmental profiles and criteria for assessment covers the tools which we shall use to evaluate and select materials on the basis of production methods, raw material availability, and energy and pollution aspects. Tables illustrate important alternatives available and key information on their environmental profile is presented. The information derives from many different, reliable sources, mainly European. They show quantifiable as well as qualitative environmental effects and should be read in conjunction with more comprehensive presentations in Parts 2 and 3. The final chapter in this section gives an introduction to the chemical and physical properties of building materials. Part 2: The flower, the iron and the sea. Raw materials and basic materials presents the materials at our disposition. The term ‘raw materials’ denotes the materials as they are found in nature, either as a single chemical compound or as a combination of several compounds. They form the basis for the production of ‘basic materials’ such as iron, cement, linseed oil and timber. These materials form building blocks in complete products. The section is divided into chapters that present the different organic and mineral materials and discuss the ecological consequences of the various ways of utilizing them. Part 3: The construction of a sea-iron-flower. Building materials discusses usage, such as roofing and insulation, and assesses the usability of the various alternatives from an ecological perspective. Descriptions are given of the practical uses of the best alternatives. This Part is divided into seven chapters: 1. Structural materials that support and brace. 2. Climatic materials that regulate warmth, humidity and air movement. 3. Surface materials that protect and shield structures and climatic materials from external and internal environments. 4. Windows, doors and stairs. 5. Fixings and connections that join different components. 6. Paint, varnish, stain and wax that improve appearance and provide protection. 7. Impregnating agents, and how to avoid them: the different impregnating substances and the alternatives. The structural, climatic and surface materials covered in the first three chapters in Part 3 represent 97–99% of the materials used in building,

Introduction

and environmental evaluations are given for each. The evaluations are mostly based on information given in Part 1 of the book. In addition to conventional environmental issues, human ecological aspects are also discussed, primarily through questions such as the feasibility of local production of building materials. The evaluation tables in Part 3 are ordered so that each functional group has a best and a worst alternative for each particular aspect of the environment. In the concluding summarized evaluation, priority is given according to the standing place of the author. In such processes, political, cultural and ethical aspects come strongly into play. In Africa for example, the raw material question is usually given high priority; in New Zealand and Argentina, factors that affect the ozone layer are taken very seriously; in Western Europe high priority is likely to be given to human toxicity. Today however, in most regions one is likely to find that global warming is the most important environmental parameter (Anderson, 2000; Lippiatt, 2007). A separate column in the tables is therefore devoted to the global warming potential (GWP) of each product. An added reason for presenting the potential climate effect of the products is that this often provides an excellent indicator of other environmental effects. A product causing high greenhouse gas emissions is very likely to be resource intensive and a source of emissions of other toxic chemicals and by-products during the production process. Studies show a clear correlation between climate-related results and results of broader environmental analyses (Strand Hansen, 2002). It is necessary to emphasize that information provided in this book represents the state of our knowledge as of the date of publication. The sciences that address the different relationships in the natural environment are complex, relatively young, and in some cases just beginning. New aspects come to light continuously, some of which can affect the whole situation. An example is chlorofluorocarbons (CFCs), which were not considered to be a problem until the 1970s when their effect on the ozone layer became known. It is also important to underline that the evaluations in this book are based on the precautionary principle. The consequences of using a material, in particular new products, should be well understood before it is taken into use. It must be emphasized that the evaluation tables describe isolated materials, and not composite constructions consisting of several elements such as often occur in buildings. This may give a slightly distorted picture in certain cases; for example, ceramic tiles and the mortar or jointing mastic used with them cannot be considered independently. In most cases, however, the tables represent a thorough basis for comparisons between products at a fundamental level.

Life span evaluations of building materials During the last 20 years many methods have been developed to evaluate the lifecycle environmental pro¢le of building materials. After some years of trial and error, several of these are now useful and e¡ective tools. Amongst those to be recommended are ENVEST (England), BEES (USA), ATHENA (Canada), EPS (Netherlands), BEAT (Denmark) and ECOPRODUCT (Norway).They are all based

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on transforming qualitative into quantitative data that are then collated into a ¢nal value expressing the environmental impacts of a material during its life span. Results for any given material may vary somewhat between systems because the evaluations are largely based upon prevailing national regulations presenting acceptable pollution limits, etc. Comparisons are further complicated by the fact that some systems weigh in economic factors, and that there is varying breadth in the environmental factors taken into consideration. The systems also have varying degrees of transparency, often including hidden evaluation procedures. Itistobehopedthat therewillbeanincreasingdegree ofcoordinationinternationally, especially in view of the global nature of the environmental issues at hand, in particular climate-related. A good degree of transparency is also important and the reasons for variations ofa national character should be easily identi¢able.

OTHER GUIDELINES FOR READING THIS BOOK All products discussed in this book are in common use or have recently been used in the construction industry. It has been beyond the scope of this book to discuss the various national or supranational (such as the EU) regulations and restrictions on singular materials. This is also a complex field where new regulations and principles, not least relating to sustainability, are fast emerging. Since the materials are arranged and discussed in groups, compound materials with components belonging to different substance groups will often be encountered, such as woodwool cement boards, made up of wood shavings and cement. In such cases, the product is listed according to which of its components has the largest relative volume. There are also cases where a material has, for example, both structural and climatic characteristics. Such materials are included in the main summaries and tables in both of the relevant sections, but the main presentation is to be found where it is felt that this material best belongs. A number of approaches and recipes for alternative solutions are described. In cases where no specific sources are mentioned, these are the author’s own proposals, and have no legal or financial liability. In some cases, recipes with less well-documented characteristics are also presented in order to provide historical and factual depth. Terms such as ‘artificial’, ‘synthetic’ and ‘natural’ are always somewhat controversial. In no way are these meant to imply an assessment of quality. All raw materials used are originally natural. In artificial/synthetic materials, however, the whole material or part of it has undergone controlled chemical and other treatment processes, usually involving high levels of heat. The extraction of iron from ore is a chemical process, whilst the oxidization or corrosion of iron by air is a natural process. The definition of biogradability used in the book is limited to materials undergoing decomposition primarily through enzymatic action of micro-organisms to carbon dioxide, methane, inorganic compounds or biomass within a limited period of time. Photodegradation, oxidation and hydrolysis of, for example, synthetic polymers, are not regarded as biogradability. The main greenhouse gases and toxic compounds are presented in Table 2.3 and Table 2.5 in Chapter 2. Here they are defined by their

Introduction

Chemical Abstract Service (CAS) registry number, since several names are often used for the same compound. Compounds listed in these tables are given a grey colour when discussed elsewhere in the text parts of Part 2 and 3. For the sake of readability, the extent of referencing given directly in the text has been limited to cases involving assertions and hypotheses that may appear surprising or controversial and therefore need to be documented in particular. A comprehensive list of suggestions for further readings is to be found at the end of each Part.

REFERENCES Commoner, B. (1972) The Closing Circle, Jonathan Cape, London. Eriksen, T.B. (1990) Briste Eller Bære, Universitetsforlaget, Oslo. Anink, D. et al. (1996) Handbook of Sustainable Building, James & James, London. Kimmins, S. et al. (1997–2000) Green building handbook, Spon Press, London. Anderson, J. and Howard, N. (2000) The Green Guide to Housing Specification, BRE Publications 390, London. Strand Hansen, S.M. (2002) The MaSe Decision Support System, NTNU Trondheim. €nst, Stockholm. Bokalders, V. (2004) Byggekologi, Svensk Byggtja Harris, C. et al. (2005) The Whole House Book, Green Building Press, Machynlleth. Kibert, C.J. (2005) Sustainable Construction, Wiley, New Jersey. Sassi, P. (2005) Strategies for Sustainable Architecture, Routledge. Hall, K. et al. (2006) The Green Building Bible, Green Building Press, Llandysul. Spiegel, R. et al. (2006) Green Building Materials: A guide to product selection and specification, Wiley, New York. Lippiatt, B.C. (2007) BEES 4.0 Building for Environmental and Economic Sustainability. Technical Manual and User Guide, NIST, Gaithersburg, August. Roaf, S. (2007) Ecohouse. A Design Guide, 3rd Edn, Architectural Press, Oxford. Wilson, A. (2007) Green Building Products. The Greenspec Guide to Residential Building Materials, New Society Publishers. Szokolay, S. (2008) Introduction to Architectural Science: The basis of sustainable design, Architectural Press, Oxford.

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