In the drive toward reduced energy consumption and consequent carbon emissions, and also reductions in fuel poverty and discomfort, the need to improve the performance of existing buildings, particularly housing is critical. To meet government targets some policy drivers are being implemented to improve the performance of existing building. In Scotland this has been through the Energy Efficiency Standard for Social Housing (EESSH) which provides funding for retrofit measures. However, very little is known about the consequences of these measures. This project developed ‘light-touch’ building performance (BPE) approaches to undertake evaluation of retrofit measures examine their effectiveness and the paper identifies these techniques and reports on the findings. Whilst in general improvements led to reduced energy consumption, various unintended consequences were evident. These included issues of thermal bridging and poor detailing, and lack of improved ventilation provision led to issues of poor ventilation and indoor air quality and reinforces the need for wider evaluation of buildings in use.