Conservation of fuel and power: Approved Document L, Volume 1 — Dwellings

O N L I N E V E R S I O N R6, R22, R23(1), L1(a) Section 11: Work to elements in existing dwellings General 11.1 This section provides guidance for work to existing elements in dwellings, including all of the following types of work. a. Renovating an existing thermal element in an existing dwelling – follow paragraphs 11.2 to 11.4. b. Making a material change of use to a dwelling – follow paragraphs 11.5 to 11.8. c. Making a change to a dwelling that constitutes a change to energy status – follow paragraphs 11.6 to 11.8. NOTE: For new and replacement elements in existing dwellings, the guidance in Section 10 should be followed. Renovating thermal elements 11.2 Renovation of a thermal element means one of the following. a. Providing a new layer through cladding or rendering the external surface of a thermal element. b. Providing a new layer through dry-lining the internal surface of a thermal element. c. Replacing an existing layer through stripping down the element to expose basic structural components (e.g. bricks, blocks, rafters, joists, frame) and then rebuilding. d. Replacing the waterproof membrane on a flat roof. e. Providing cavity wall insulation. 11.3 If a thermal element is renovated and one of the following applies, then the whole of the thermal element should be improved to achieve at least the U-value given in Table 4.3, column (b). a. More than 50% of the surface of the individual thermal element is renovated (see paragraph 11.4). b. The work constitutes a major renovation. A major renovation is when more than 25% of the surface area of the external building envelope is renovated. NOTE: If paragraph 4.13 applies, Appendix C provides examples of renovation of an existing thermal element that are technically, functionally or economically feasible. 11.4 When assessing the percentage area that will be renovated of an individual thermal element, consider whether the element is being renovated from the outside or the inside, following Diagram 11.1 and Diagram 11.2, respectively. Building Regulations 2010 Approved Document L Volume 1, 2021 edition 67 O N L I N E V E R S I O N