Assessing the sustainability merits of retrofitting existing homes

The UK government has agreed to a 26% reduction in greenhouse gas emissions by 2020 and an 80% reduction by 2050, against a 1990 baseline. Britain's approximately 26 million existing homes account for 27% of total UK greenhouse gas emissions. Given the low-build rate for new homes, today's homes will comprise at least 80% of the 2050 housing stock. Therefore, it is essential that significant improvements are realised to existing homes if the UK is to meet its sustainability objectives. This paper develops a building rating system designed to assess the sustainability merits of existing home retrofits and to indicate the success of a range of retrofit measures. With the methodology applied to six case studies, performance of the retrofit measures adopted and their prioritisation are discussed, together with the effectiveness of a retrofit building rating system. The creation and adoption of a purpose-designed building rating system, such as the one described and demonstrated here, with escalating mandatory performance levels in energy and water efficiency, would help to drive improvement in existing homes. Such an approach would be used to rate existing homes, galvanise stakeholders around a common framework and provide long-term visibility to the marketplace. It must be integrated with existing building regulations, planning mechanisms, incentive programmes, and assessment requirements such as energy performance certificates. Encouraging action now will not only result in quality improvements to the existing housing stock and a reduced ecological footprint but will also build resilience in energy and water systems and facilitate adaptation to future climate change.