This paper presents the results of two possible scenarios for energy use and carbon dioxide emissions of the UK housing stock, developed using the BREHOMES model. One of them represents what is likely to happen if current trends continue, and is an update to the scenario in BRE Information Paper IP9/94. The second represents what could happen if the rates of uptake of energy efficiency measures increased. It shows that reductions in carbon dioxide emissions could be considerable: by 2020 they could amount to about 250 PJ (or 21 million tonnes of CO2) per year, representing roughly 13% of the corresponding energy use and CO2 emissions both now and, at current trends, in 2020. Furthermore, the cost savings if rates of energy efficiency improvement increase, are shown to be considerably greater than the extra expenditures when assessed over the period up to 2020. 5 pages.