Buildings of the future must be designed and constructed to reduce energy demand. From a thermal point of view, technologies to minimise heating needs already exist. But in order to reduce future cooling requirements, more positive action will be required. This applies both in commercial buildings, where cooling demand is already significant, and in the domestic sector, where air conditioning is gaining a foothold. A further problem in the housing sector is the rising electrical demand from appliances, which has increased significantly in recent years. In addition to changes in construction practice, such as using means to mitigate the effects of warming climates, better, more sophisticated control systems must be more fully utilised, such as the automatic switching off of appliances, and advanced controls and metering. A range of alternative energy sources should be integrated in and around single buildings and groups of buildings. Group scale allows more flexibility and will provide higher efficiencies and better control, and is thus the favoured option. Most renewable energy technologies are already understood and the majority are technically proven, though costs are still high in some cases. A combination of renewable energy and storage mechanisms will be needed to decouple energy supply from energy demand. Buildings must be constructed in flexible ways so that they can adapt to allow new technologies to be used. A crucial issue is space for energy storage mechanisms and for alternative fuels.