Chapter 5 Materials selection - Elsevier...Chapter 5 Materials selection In which we seek to give the reader a sound and broad grasp of the issues and priorities affecting materials

Chapter 5Materials selection

In which we seek to give the reader a sound and broad grasp ofthe issues and priorities affecting materials selection in thedesign of sustainable places, buildings, services and objects anda realistic perspective on the range of issues, including theirinvisible qualities, which should affect decision-making.

‘Hygroscopic building materials are 9 times more effectivethan mechanical ventilation in controlling indoor relativehumidity’

VTT Espoo Finland

Ch05-H6394.qxd:Chapter 5 11/22/07 9:08 AM Page 113


Materials selection 115

Contents

(Facing page)Andersen House

The moisture from the building is vented behind this sacrificialtimber layer (Architects: DagRoalkvam and Rolf Jacobsen;

photo: Dag Roalkvam

(Previous page)Solid timber roof at Glencoe

visitor centre(Photo: Michael Wolshover; photo

permission: Gaia Architects)

Case studies

5.1: Timber College, Lyss 119

5.2: Prisma mixed development, nuremburg 120

5.3: Linacre College, Oxford 123

5.4: Glencoe Visitor Centre, Glencoe, Argyll 126

5.5: Edinvar Housing Association, Edinburgh 130

5.6: Fairfield, Perth 135

Introduction 116

The life cycle approach 117

Resource base 118

Embodied pollution 118

Extraction 121

Processing and production 122

Impact in use 125

Detailing 125

Toxicity 125

Passive environmental control 127

Local issues 129

Final destination 131

Durability 131

Maintenance 132

Lifespans 132

Choices – the 5 Rs 133

Materials – handy hints and tips 136

Bibliography 137


IntroductionEcological building design is characterised bythe use of natural materials with a minimum of processing and transportation; and anemphasis on healthy, non-toxic specification to minimise pollution. Ideally materials should also contribute to passive forms ofenvironmental control.

Many attempts have been made to create acoordinated and comprehensive analysis toolfor materials in the construction industry thatcan enable those specifiers, who are minded to do so, to make objective decisions about material selection. Many of these take a lifecycle approach. A number of the techniquesare helpful, and there is ongoing improvementas information evolves, but none are compre-hensive. Nor are they ever likely to be so.

In part this is because of the complexity of the issues but alsobecause the ‘sustainability’ of most materials owes much to thesourcing and handling, the way in which they are used, and thecare that goes into their detailing and maintenance. This cannotas yet be completely covered by any analytical process that isreliant on being uniformly applicable.

A contributory factor is doubtless to do with the relationshipbetween products and design, and the opportunities for addedvalue. There is still widespread ignorance about how to usematerials in their natural state and many manufacturers prefer toavoid scrutiny.

The most valuable approach in most circumstances is to becogniscent of the issues and have access to up-to-date guidance.It will generally be necessary to compare options and relativeimpacts in a particular circumstance. These issues thereforeremain within the realm of compromise and judgement, a realmfamiliar to designers. However it extends the territory such thatdistance, manufacture, human rights, biodiversity and pollutionmight all be part of a balanced judgment. Importantly thisshould not be restrictive on design, if thought about intelligently,but should open up new creative opportunities. For examplethinking about the future of a rare or energy intensive material isas important as looking at its past.

Kamen, GermanyHousing development, part of Emscher Park regeneration

designed using 100% eco-labelled materials(Architect: Joachim Eble Architects; Photo: Howard Liddell)

116 Sustainable Construction

Materials selection

Lisbon Expo StationMaterials selection does not exclude any architectural style

(Architect: Santiago Calatrava; Photo: the author)



The life cycle approachThe main questions to ask of a material specification choice are:

1 What is the Resource Base? – Where is it from and how muchis left?

2 What is the Embodied Pollution? – What has been done to itand by whom? – There is often an ethical component.

3 What is its Impact in Use? – What effects does it have onpeople and the wider environment?

4 What is its Final Destination? – What will happen to it at theend of its life?

In general it will not be practical, or possible, to arrive atdefinitive answers to all or any of these considerations. Nor is itfeasible for most specifiers to assess each and every componentagainst each and every consideration. In the face of suchlimitations, more important is a genuine commitment toachieving the best result. A basic knowledge of the issues andopportunities can readily lead to sensible assessments andsubstitutions. Conversely, a basic disregard for good sense,pollution and ethics undermines the serious advances that arepossible. Ultimately, the assessment is made by the environment.

Traditional timber fascia detail, nineteenth-century railway station, Killin Pier(Photo: Howard Liddell)

Eco-label for building products (‘Swiss Roll’)

Manufacture

Maintenance

Disposal

Utilisation

1

2

3

45

6

7

8

Low impact High impactMedium impact

“Swiss Roll”A material and product assessment method that looks at

cradle to grave issues



Resource baseCertain resources are becoming extremely rare and the use ofremaining stocks should be treated cautiously, especially wherethey are known to support threatened habitats or where thereare known to be uses that should take precedence.

Most rare materials used in construction can be substituted byother, less rare or renewable materials. However, there are fewabsolutes. These guidelines have to be taken within the contextof what is appropriate and possible.

• Renewable materials should take precedence over non-renewable ones.

• Reused or recycled materials or components should takeprecedence over equivalent ‘virgin’ elements.

• Sourcing of materials from areas that are particularly fragile – in respect of their aesthetic, community or ecology should be avoided.

• Materials with significant reserves remaining should be usedin preference to those with smaller reserves.

• Materials should be used as efficiently as possible and allow for their eventual reuse or recovery – especially where using a material with minimal reserves.

Many metals commonly used in the construction industry haveextremely limited estimated reserves. World Resource Instituteestimates suggest that we may have only a further 10–12 yearssupply of lead and zinc. This compares poorly with an estimated210-year supply of bauxite – the main source of aluminium,which would be a good substitute in most circumstances. Also,recycling of aluminium is extremely well developed.

Most plastics derive from the world’s oil reserves. The use ofrecycled plastic components makes environmental sense, except

where recycling contributes to additional and avoidable pollution.However, many recycled materials remain more expensive than‘virgin’ equivalents and meeting appropriate building standardsmay require pre-planning, which should be allowed for.

Embodied pollution – whathas been done to it and bywhom?Huge damage is done to the local and global environment andto the health of workers and others through the extraction,production and distribution that make up the constructionindustry supply chain. Some manufacturers are involved inethically questionable practices, whilst others have explicit andforward thinking policies on environmental and social issues andmay be willing to provide good information on their impacts,and strategies. It is up to the specifier to determine the relevanceand priorities. It is notable that purchaser power is increasinglyresponsible for changes in government policy and thatincreasing numbers of companies are developing guidelines toaddress their responsibilities.

All materials contain embodied energy, which is a form ofembodied pollution, but many conventional building materials alsocontain additional elements, as a consequence of chemicalprocessing, which are known to be toxic to humans and or wildlife.

This includes concrete, PVC, MDF, most glues, paints andfinishes. This “embodied pollution” can impact throughout theproduct life; on employees in the manufacturing process, tobuilding occupants through off-gassing or leaching in use andeventual pollution through recycling or disposal.

Materials selection, timberTimber from a local source, used in an untreated form and

detailed for long life, is a good choice. However, if brought hugedistances, treated with polluting materials such as CCA and

poorly detailed, it is not (Photo: Howard Liddell)

Embodied ToxicityPlastic is being recycled into a range of useful components,

such as this ‘squidgy tarmac’, but we have to be carefulabout embodied toxicity (Photo: the author)


This forest training centre in Switzerland was visited in 2005 by a group of Scottish andScandinavian building designers interested in newdevelopments in wood construction.

The building, occupied in 1998, is owned by afoundation from 11 cantons. It was originallyintended to be a concrete construction but, withthe timber industry in decline, the directorinsisted on a timber construction.

The primary construction comprises 300 silver fir columns with steel consoles. The floor construction comprises suspended MDF acousticceilings below rough pine roundpole and cheaptiles made of recycled materials. All the furnitureis red heartwood beech. In total, about 2000m3 oftimber was used, equivalent to 1.7 hours Swiss forest growth. It is heated from a wet wood biomass boiler using in total 650m3/annum.

Case Study 5.1:

Timber College, LyssArchitects: Itten and Brechbuhl, 1998


Photo: the author


Despite being in the centre of a German city and having to comply with stringent building control and fire regulations, this nine-storeymixed development manages to achieve a veryhigh standard of specification in terms of environmentally sound materials – notably the finishes. Where possible, floors are of mass timberto form an equivalent to concrete beam and blockflooring. Concrete is used only where absolutelynecessary. Timber finishes are used throughout,and the paint and other surface treatments are alllow or zero emission.

This is probably the world’s largest complex thatcan be defined as an ecological design project. The ground floor is a shopping precinct, the next three floors are offices and the top floors are residential.

The inner courtyard offers a secure environmentfor a kindergarten, which serves the on-site housing. All the commercial properties get theirpreconditioned ventilation from the large solaratrium.

Passive solar and natural ventilation strategiesutilise water flows and planting in atrium spaces. The water strategy is based on catching,conserving and recycling on site.

This scheme sought to use as many recycled orreclaimed materials as possible, sourced withinbudget and time constraints. The aluminium roofhas the potential to be reused as a high valuematerial in perpetuity but there may be energypenalties.

The housing scheme comprises a three-storeyblock of flats, a row of houses and cottage flats.The block of flats face south and the L-shapedplan forms a semi-private enclosed garden andchildren’s play area.

Case Study 5.2:

Prisma mixed development, NurembergArchitects: Joachim Eble Architects, 1997


Photo: Joachim Eble Architects


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Chapter 5 Materials selection - Elsevier...Chapter 5 Materials selection In which we seek to give the reader a sound and broad grasp of the issues and priorities affecting materials