The document provides information on thermal regulations in England, including details on Part L of the Building Regulations which specify energy efficiency requirements. It outlines the approved documents that contain technical guidance, such as L1A, L1B, L2A and L2B. The regulations require certain maximum U-values be achieved for insulation depending on the type and location of the building and construction element (e.g. wall, floor, roof). U-values measure heat loss and insulation performance, with lower values indicating better insulation. The regulations and guidance on U-values can be found on the Planning Portal website.