Materials

Why choose to use sustainable building materials rather than those more commonly used? There are two main factors driving the choice: global environmental issues and performance benefits.

The choice of material affects many global issues already introduced in Green Street, but this is what it means for materials:

Climate change

The majority of CO2 emissions result from energy used during the life of the building, and reducing that energy is covered elsewhere. However, construction materials themselves account for a significant amount of energy use. This is called embodied energy, and it includes the energy involved in the manufacture, transport and eventual disposal of the material.  It can be reduced by choosing materials that are locally sourced, require minimum energy for their manufacture and disposal, and have a long lifetime or can be re-used.

Resource depletion

Many conventional building materials are products of the petrochemicals industry, but oil reserves are likely to last less than 40 years.  Materials such as copper, zinc and tin are also likely to run out within 40 years.  The use of materials from non-renewable sources should be minimised, and where possible, materials should be selected from sustainably managed renewable sources, or manufactured from recycled products.

Environmental pollution

The manufacture of many conventional construction materials involves the use of highly toxic chemicals, and may result in significant atmospheric pollution and toxic waste. In addition, their ultimate disposal through incineration or landfill can result in further atmospheric pollution, or the leaching of toxins into the ground. Where possible, materials that use harmful chemicals during their manufacture or disposal should be avoided. Ideally, materials should be re-usable, recyclable or biodegradable.

Choosing sustainable materials can result in several performance benefits over more conventional materials. For example, the moisture-absorbing properties of many natural insulation materials can help to regulate the indoor climate, and their use in timber-frame constructions can help protect the structural timber from moisture damage, eliminating the need for preservative treatment.

Using natural insulation materials, natural paints, and natural flooring helps to improve indoor air quality.  Condensation can be reduced, and the anti-static nature of natural paints can reduce the build-up of dust. The emission of unpleasant chemical fumes, referred to as off-gassing, from synthetic floor coverings and adhesives can be minimised.

Construction and demolition waste accounts for a significant proportion of UK waste. The eventual disposal of building materials during future refurbishment or demolition, needs to be considered when those materials are selected. In addition to the environmental benefits already mentioned, materials that can be re-used or recycled, or those that naturally biodegrade, are likely to be more easily and cost effectively disposed of in the future.

Checklist for selecting sustainable materials

The following general criteria should be considered for the selection and specification of materials that reduce negative environmental impacts, and improve internal conditions:

• Natural, non-toxic raw materials, from renewable resources wherever possible, extracted or harvested by environmentally sound methods, for example timber or cork.
• Maximum use of recycled materials, for example cellulose insulation made from recycled newspapers.
• Lowest possible embodied energy in the product?s manufacture and transport. Sourcing locally can help achieve this.
• Non-polluting manufacturing process, safe to the workforce
• Safe, non-toxic installation or application of the product.
• Safe, non-toxic use of the building after construction.
• Lowest possible energy requirement for running the completed building.
• High level of internal comfort in the completed building.
• Re-usability, recyclability or safe disposal at the end of the building?s or component?s lifetime.

Various manufacturers may produce what appear to be similar materials.  Yet different processes, components and additives may be involved. In sourcing materials, it is important to obtain the manufacturer?s technical specifications for the specific product to ensure they reveal the full environmental credentials.

The suitability of a particular material for an application will depend on a building?s structure and state of repair, the performance required, occupancy patterns, and on other materials being used. We have given guidance on what materials may be suitable for particular applications, but we recommend you take experienced professional advice before specifying a material for a specific application.