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 on the conservation of fuel and power. These approved documents include guidance for new builds and existing dwellings as well as other buildings. The regulations require certain U-values be met for insulation depending on the type and location of the building project. U-values measure heat loss and insulation performance, with lower values indicating better insulation. The regulations set U-value targets that must be met when carrying out new builds or refurbishment projects.