Life cycle assessment (LCA) is used to total up the environmental impact of a product’s supply chain. Providing sufficient data is available on the product’s composition and supply chain, LCA can be used to work out the environmental impact of almost anything from a can of baked beans to a car. The results of the LCA are presented in an environmental product declaration (EPD).
In construction, more and more construction product EPD are being published by manufacturers for their products. This provides a great source of data but, unlike with a can of beans, a bag of sand is not the final product – the building is. So using construction EPD in isolation to inform lower impact design is not going to be very effective.
For example, the nutritional information on food products are given per portion. It would not be useful if the label on a can of baked beans showed the energy, sugar and salt content of the separate raw ingredients: 1 m3 of beans, 1 tonne of tomatoes, 1000 litres water – you get the idea. This would provide nothing useful on the nutrition of a portion of baked beans because the can contains a cooked mixture of these ingredients in different proportions. The same principle applies to buildings. EPD are a great source of data but there is little benefit for a design team in knowing the environmental impact of individual construction products like 1 steel beam, 1m3 of timber or 1 can of paint.
Enter building LCA! Building LCA is no different from an LCA on a can of beans, it just means the product undergoing LCA is a building. Building LCA tools are used to total up the environmental impact of the building, based on the environmental impact coming from the supply chain of the construction products it is made from (sometimes operational energy, operational water, future maintenance and demolition are also included).
The leading standards in construction LCA are clear that “The purpose of an EPD in the construction sector is to provide the basis for assessing buildings…and identify those which cause less stress to the environment”1 – in other words, you need to do building LCA.
What is BREEAM doing about building LCA?
BREEAM agrees with the principle set out in the standards and has been introducing building LCA into our schemes since 2011 when two exemplary credits were included in BREEAM UK New Construction for building LCA. BREEAM International has included building LCA since 2013. More recently, the 2018 update of BREEAM UK New Construction completely replaced the old Green Guide approach with building LCA.
Why not stick with the Green Guide?
For over 20 years, the Green Guide has been the primary way BREEAM has assessed the environmental impact of construction products in buildings and it was last updated in 2008. The Green Guide avoids the problem of using construction product EPD in isolation because it is based on choosing from a range of environmentally rated typical construction build-ups. Each construction build-up includes a typical arrangement of products for a building element (e.g. external walls, roofs, floors etc.). As the name suggests, this provides a useful guide in selecting lower impact construction build-ups, but using the Green Guide does not offer the level of building specific accuracy now possible in building LCA.
Although building LCA standards have been available since 2011, BREEAM UK New Construction has continued to use the Green Guide (with building LCA included as an exemplary level achievement) because, until recently, building LCA has been too specialist for most design teams.
Now that building LCA is better understood with greater traction and several suitable tools are available, BREEAM has fully embraced it within BREEAM UK New Construction 2018 – with the aim of enabling and encouraging the construction industry to rise to the challenge of further reducing the environmental impact of buildings.
1(BS EN 15804:2012 “Sustainability of Construction works – Environmental Product Declarations – Core rules for the product category of construction products”)
Take a look at some of the most sustainable buildings in the world on the BREEAM Case Studies.