Principles of materials
The correct selection of materials for a specific construction project can depend on a number of factors and influences which will have roots within the different pillars of sustainability (Environmental, Social and Economic). The impacts of both material selection on the building and in sourcing those materials should be considered.
For example Hertfordshire has considerable sand and gravel deposits and mineral extraction is an important contributor to Hertfordshire’s economy. However, even well managed minerals extraction generates noise, dust and waste, uses significant amounts of energy and manifests itself in the form of heavy goods vehicles on the roads.
Constructing buildings with a high thermal mass material such as concrete may improve the buildings thermal efficiency and minimise operational carbon emissions, however The production of cement used in concrete results in a significant proportion of greenhouse gas emissions in the UK. This is a result of the chemical process of calcification, and to the fossil fuels used for heating to drive the calcification process.
Whilst progress has been made in improving the fossil fuel consumption of the manufacturing process, the basic chemical process cannot be changed.
For each tonne of concrete used from virgin stock 134.8kgCO2 is released into the atmosphere.
Although timber is considered a sustainable material, it is essential that the forests which supply the timber are well managed to avoid deforestation, associated loss of habitats and changes to the character of the landscape and ground conditions. Risks of flooding and landslides can also increase
It is therefore important to consider the wider impacts of a material when selecting/ specifying for a building project.
Principles of sustainable materials
Re-use and efficient use of materials
Defining a ‘sustainable’ material or product can be a subjective term and in the case of construction materials it can be more of a case of selecting the least unsustainable product. Good design and specification can lead to the same construction outcome utilising fewer products or with at a lower cost to the environment.
There are two important Stages to sustainable materials selection:
1: Minimisation of environmental damage, using life cycle principles
2: Efficient use of materials, through application of the waste hierarchy
Environmentally friendly materials
Materials with the lowest environmental impact tend to have only minimal processing requirements. Examples of this include the use of timber and insulation made from sheep wool.
The use of petrochemicals in materials have significant environmental impacts as they are derived from fossil fuels and can have further implications for indoor air quality and occupant health. The specification of alternatives is a more environmentally friendly approach and examples include, amongst others:
- water based paints
- insulation from organic sources or from naturally occurring minerals, such as cellulose or cork board, or mineral wool
Transport of building materials involves energy use, which counts towards the overall environmental impacts of the material. The amount of energy used for transport, particularly in the case of heavy or bulky materials, can be significant.
The most effective way in which to reduce these impacts is to limit the distances that materials are transported. A best practice approach would be to limit the radius for sourcing high mass materials to a radius of, for example, 30 miles. Alternative good practice measures include:
- Avoidance of international sourcing, for example use of UK rather than Chinese slate
- Organisation of deliveries to minimise trips and ensure that lorries have another load to transport on the return journey
- Use of route planning software to avoid unnecessary diversion or delays
- Use of fuel efficient vehicles,
- Monitoring distance travelled and efficiency of vehicles for transport of materials to and from site
- Fuel efficient driver training
Demolition should be carried out as a last resort, where the building has deteriorated beyond the point where it can be reused. Wherever practicable, demolition should take the form of careful deconstruction to maximise the potential for re-use of materials.
Re-use and efficient use of materials
Re-use of materials and/or use of environmentally friendly materials should be viable on any project, whatever its scale, location or functional specification. Materials reuse can be challenging, as it requires careful deconstruction and storage of materials until such time that the materials are required for reuse. However, use of new materials that are ‘environmentally friendly’ is now commonplace as most greener materials no longer cost any more than ‘standard’ materials; nor do they differ in terms of aesthetic or functional qualities. The recovery rate from non-hazardous construction and demolition waste in the UK in 2012 was 86.5 per cent. There is an EU target for the UK to recover at least 70 per cent of this type of waste by 2020.
Benefits of sustainable material management
Sustainable material management delivers lots of benefits:
- Reduced use of virgin materials.
- Reduced waste generation.
- Reduced environmental impacts associated with materials production and transportation.
A - PVC-U framed windows
B - Concrete upper floor
C - Plasterboard partitions with zero recycled content
D - Foam insulation (polyurethane / phenolic foam)
E - Synthetic carpet with foam underlay
F - Solvent based paints
G - Rainscreen cladding, e.g. aluminium or plastic laminate
H - Slate imported from international sources, e.g. Spain or China
A - Timber framed windows
B - Hollow precast concrete upper floor
C - Plasterboard partitions with recycled content
D - Sheep wool insulation
E - Ceramic/stone/terrazzo tiles, or linoleum
F - Wool carpet with recycled rubber underlay
G - Water based paints
H - Timber cladding
I - Green roof - sedum or turf