The most important part of environmental sustainability in a refurbishment project is minimising the use of energy, particularly energy from nonrenewable sources, to reduce the contribution to climate change. There are two aspects: embodied energy in the refurbishment process and energy in use in the subsequent lifetime of the building. Reducing lifetime energy use is usually by far the larger component and the area in which the largest impact can be made in refurbishment, even reducing it to zero in some cases with the judicious use of renewable energy sources. This chapter summarises the actions that can be taken in the design to minimise energy use in the operation of a building being refurbished, in its fabric, services, controls, etc. Chapter 12 describes the other main areas where environmental sustainability can be improved, reducing water use, providing recycling facilities, choosing materials for the works and landscaping on and around the building.