The existing residential building stock accounts for a substantial portion of worldwide energy consumption and greenhouse emissions. Improvements to the thermal performance of existing buildings is a vital activity to mitigate climate change, and often has additional benefits in the form of improved comfort, health and well-being for occupants. Despite the extensive body of literature in this area, it remains a difficult task to assess the performance of retrofit packages in occupied residential buildings.

This report is the first report of the ‘Energy Savings 2030’-project which seeks to help the Coalition for Energy Savings to produce a robust and timely input to the 2030 policy discussion. It brings together and summarises recent empirical evidence on costs and benefits of energy efficiency measures. The evidence gap in terms of reliable ex-post data is well known. In the majority of cases results from ex-ante modelling studies inform the debate. The research carried out for this report confirms the persistent gap in publicly available ex-post evaluations of energy efficiency programmes.