The research and evaluation needs to support radical decarbonisation in the built environment are examined for the UK. Since buildings account for approximately 40% of UK energy demand, energy use in buildings will need to be transformed if ambitious climate policy objectives are to be met. In the context of wider energy system change, the needs are for greater efficiency, greater use of electric technologies such as heat pumps as electricity become cleaner, and the use of renewable heat such as biomass. At the same time, the introduction of smart technology offers new opportunities to measure and evaluate changes in demand patterns and the impact of policy interventions. The paper notes that the technical and social dimensions of radical decarbonisation are intimately intertwined. Therefore, social and economic research has a vital role to play in supporting the design and implementation of effective policy, taking advantage of new data-collection opportunities. Drawing on lessons from other policy domains, the paper explores the role that rigorous policy evaluation techniques, little used in the energy domain, could play. It identifies a range of concerns, relating to the political sphere, policy delivery and consumer acceptance, that would need to be addressed.