We often focus on the overall reduction on the use of energy from fossil fuels, and rightly so as about half the energy use in Britain goes on heating and lighting buildings, of which about 30% is within the domestic sector.
Meanwhile there is a significant amount of energy used in the production of the houses themselves; producing and transporting the materials and the construction process.
This is termed the ‘Embodied Energy’. It becomes an important factor when we are looking to design a building to be more energy efficient. Some simple measures include using:
- Second-hand materials where possible (and materials with high recycled content in preference to new materials)
- Minimally processed rather than highly manufactures products
- Locally produced materials in preference to those sourced from far away or imported products
It is estimated that up to half the embodied energy content of a building could be reduced by following these simple steps.
This is the starting point but does not consider all of the explicit environmental impacts of building materials.
The most commonly recognised approach is the ‘Life Cycle Analysis’ (LCA) which as the name suggests tracks the impact of materials during extraction, production, transport, construction, maintenance, repair, replacement and ultimate disposal.
Only by taking the LCA approach can we adequately compare various building products against each other and make the most informed decision on the best products for our eco build.
The LCA forms the basis of the Green Guide to Housing Specification (The Green Guide) published by BRE.
The first edition of The Green Guide series was published in 1996 and aimed to provide a simple ‘green guide’ to the environmental impacts of building materials which is easy-to-use and soundly based on numerical data.
The Green Guide is part of BREEAM (BRE Environmental Assessment Method); an accredited environmental rating scheme for buildings. The Green Guide contains more than 1500 specifications used in various types of building.
Since the first edition, information on the relative environmental performance of some materials and components has altered reflecting both changes in manufacturing practices, the way materials are used in buildings, and our evolving environmental knowledge.
The guide has been continually updated and provides an essential representation of data set out as an A+ to E ranking system, where A+ represents the best environmental performance / least environmental impact, and E the worst environmental performance / most environmental impact.
The Green Guide rating is a measure of overall environmental impacts covering a total of 13 issues, which includes the following in order of the highest relative weighting:
Climate change, Fossil fuel depletion, Stratospheric ozone depletion & Human toxicity
By evaluating the performance of materials and building systems against these specific environmental impacts, which have also been ranked on an A+ to E basis, it is possible to select specifications on the basis of personal or organisational preferences or priorities, or take decisions based on the performance of a material against a particular environmental impact.
The Green Guide aims to present complex Life Cycle Analysis information in a form which is easy to use basing it on each building element, and as such it is an essential consideration in the early design and planning phase of any new build or eco retrofit project.
For more information: http://www.bre.co.uk/greenguide