The Growing Importance of Life-Cycle Assessments for Sustainable Building
Meeting targets to reduce carbon emissions by 2050
Carbon emissions from operating our buildings account for nearly half of the 550 MtCO2 emitted annually in the UK, and must be tackled if we are to meet the target of an 80% reduction in emissions by 2050. The mass roll-out of refurbishment measures is crucial in addressing emissions from existing stock, whilst the energy efficiency demands of new buildings are steadily increasing. By 2016 for domestic properties and 2019 for others, all new buildings will be required to be ‘zero-carbon’ in operation.
Built to 2010 regulations, emissions from the construction of a typical masonry dwelling account for around 20% of associated carbon emissions over its life; by 2013 this will be more like 50%, and by 2016, all emissions associated with a dwelling will be embodied within the manufacture and transport to site of construction materials. It is crucial that we start assessing and taking action to minimise these emissions now. At present, there is little legislation to promote the assessment of life-cycle emissions, although some guidance exists on methodology, most notably in the form of BS EN ISO14040/14044 and PAS2050.
Choosing Sustainable Materials
Assessment of the carbon embodied within a building project must occur both in the design and construction phases. This is to allow feedback to practitioners on the accuracy of their predictions. In design, a tool exists that can consider both simple and more complex designs, assessing an array of scenarios and making recommendations on how best to minimise embodied carbon. Suggestions may include increased use of timber, waste product in cement production, or the sourcing of locally manufactured prefabricated components. It is clear that the use of renewable, recycled and local materials improves the environmental credentials of a development, but it is useful to quantify this benefit. Life expectancies of different materials should also be accounted for.
Ideally, responsibility for data collection on-site would be allocated to an individual. However, all those involved in construction should be made aware of the process. Keeping a record of materials delivered is standard site practice, but documentation should be widened to include information of the type of delivery vehicle and distance travelled.
There are well known tools for predicting emissions from operation of a building, including SAP and SBEM in the UK. These may broadly estimate emissions from initial building services and design but they do not allow for changes in design and specification over a building’s life; it must be acknowledged, however, that this can be an extremely difficult thing to do.
Choice of materials and processes at the design stage will also impact on emissions at decommission. Many materials can be reused or recycled, and practices such as use of lime-mortar, reduced use of paints and ‘design for deconstruction’ increases their potential. Constructing buildings with longer life expectancies and easily replaceable (yet durable) components reduces life-cycle impact.
Considering the Environment
Considering the environmental implications of materials and design over the life-cycle of a building can reduce emissions in all three phases of its life (i.e. construction, operation and decommission). With zero-carbon targets fast approaching, such assessment is becoming vital. Developers who realise this will see benefits such as improved environmental credentials of bids for work, clear dedication to the sustainability of their projects, and crucially in the current climate, the ability to ‘outgreen’ their competitors.
Anthony Probert is Phlorum’s Sustainability Consultant and an expert in the sustainable design of buildings. As well as a Code for Sustainable Homes assessor, Anthony undertakes SAP assessments, energy statements, renewable energy feasibility studies and life-cycle carbon assessments