This paper sets out the results of the York Energy Demonstration Project and discusses its implications for the modernisation of low rise housing in the UK. The project consisted of three schemes, which were carried out in the early to mid 1990s and monitored over a 2-year period. Results indicate that modem1sation schemes have a very important part to play in reducing C02 emissions and that improvements in the region of 50% can be achieved at modest cost using well proven (early 1980s) technology.