In the Energy White Paper of 2003 the UK Government set itself the goal of working towards reducing carbon emissions by 60% by 2050. This report explores the scope for achieving such reductions within the housing stock through energy efficiency measures and the uptake of low carbon technologies, such as renewable energy. It examines the current potential for such improvements, including assessments of their cost-effectiveness. It also assesses the effects that past energy efficiency policies (such as grants, energy labelling and Building Regulations) have had. Extensive tabulations of hard-to-find data on cost-abatement analyses and past energy efficiency policies are included. Finally, using a detailed bottom-up modelling approach, it considers what could happen in the future, exploring a series of five scenarios that progressively introduce increasing levels of energy efficiency improvements and low carbon technologies. It shows that, although very challenging, a 60% reduction by 2050 is feasible and might actually be achieved cost-effectively. 80 pages. Updates and extends BR435, published in 2001.