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

O N L I N E V E R S I O N L1(a) Table 4.1 Limiting U-values for new fabric elements and air permeability in new dwellings Element type Maximum U-value(1) W/(m2·K) All roof types(2) 0.16 Wall(2) 0.26 Floor 0.18 Party wall 0.20 Swimming pool basin(3) 0.25 Window(4)(5) 1.6 Rooflight(6)(7) 2.2 Doors (including glazed doors) 1.6 Air permeability 8.0m3/(h·m2) @ 50Pa 1.57m3/(h·m2) @ 4Pa NOTES: 1. Area-weighted average values. 2. For dormer windows, ‘roof’ includes the roof parts of the windows and ‘wall’ includes the wall parts (cheeks). 3. The U-value of a swimming pool basin (walls and floor) calculated according to BS EN ISO 13370. 4. If performance requires thicker glass to be used, an equivalent window unit with standard thickness (6mm) glazing should be shown to meet the required standard. 5. Including roof windows and curtain walling. 6. U-values for rooflights or rooflight-and-kerb assemblies should be based on the developed surface area of the rooflight (U -values), which is often greater than the area of the roof opening. Further guidance on U -values is d d given in the Building Research Establishment’s BR 443 and the National Association of Rooflight Manufacturers’ Technical Document NTD02. 7. The limiting value for rooflights also applies to kerbs that are supplied as part of a single rooflight-and-kerb assembly sourced from the same supplier and for which the supplier can provide a combined U -value for the d assembly. An upstand built on site should not exceed a U-value of 0.35W/(m2·K). NOTE: To meet the target fabric energy efficiency rate set out in Section 1, the energy efficiency of some elements will need to be significantly better than the limiting standards in Table 4.1. Limiting standards in existing dwellings New and replacement elements 4.7 New fabric elements in existing dwellings should meet the limiting standards in Table 4.2. 4.8 The U-value of a replacement fabric element in an existing dwelling should both: a. be no worse than that of the element being replaced b. meet the limiting standards in Table 4.2. 4.9 Guidance on when a new element must meet the standards in Table 4.2 is given in Section 10. Elements that should meet the standards include both of the following. a. Elements in extensions to existing dwellings. b. New or replacement elements in existing dwellings. 4.10 If windows or fully glazed external pedestrian doors cannot meet the requirements of Table 4.2 because of the need to maintain the character of the building, either of the following should be met. a. These fittings should not exceed a centre pane U-value of 1.2W/(m2·K). b. Single glazing should be supplemented with low-emissivity secondary glazing. 24 Approved Document L Volume 1, 2021 edition Building Regulations 2010 O N L I N E V E R S I O N