Conservation of fuel and power: Approved Document L, Volume 2 — Buildings other than dwellings

O N L I N E V E R S I O N L1(a) Table 4.1 L imiting U-values for new or replacement elements in new and existing buildings and air permeability in new buildings Element type Maximum U-value(1) W/(m2·K) or air permeability Roof (flat roof)(2) 0.18 Roof (pitched roof)(2) 0.16 Wall(2)(3) 0.26 Floor(4)(5) 0.18 Swimming pool basin(6) 0.25 Windows in buildings similar to dwellings(7)(8) 1.6 or Window Energy Rating(9) Band B All other windows,(8)(10)(11) roof windows, curtain walling 1.6 Rooflights(12)(13) 2.2 Pedestrian doors (including glazed doors)(14) 1.6 Vehicle access and similar large doors 1.3 High-usage entrance doors 3.0 Roof ventilators (including smoke vents) 3.0 Air permeability (for new buildings) 8.0m3/(h·m2) @ 50Pa NOTES: 1. Area-weighted average values, except for new windows, rooflights and doors in existing buildings. 2. For dormer windows, ‘roof’ includes the roof parts of the windows and ‘wall’ includes the wall parts (cheeks). 3. If meeting such a standard in an existing building would reduce by more than 5% the internal floor area of the room bounded by the wall, a lesser provision may be appropriate. 4. The U-value of the floor of an extension may be calculated using the exposed perimeter and floor area of either the whole enlarged building or the extension alone. 5. If meeting such a standard in an existing building, would create significant problems in relation to adjoining floor levels, a lesser provision may be appropriate. 6. The U-value of a swimming pool basin (walls and floor) calculated according to BS EN ISO 13370. 7. For example, student accommodation, care homes and similar uses where the occupancy levels and internal heat gains are essentially domestic in character. 8. If other performance (e.g. wind load, safety, security or acoustic attenuation) requires thicker glass to be used, an equivalent window unit with standard thickness glazing should be shown to meet the required standard. 9. The methods for calculating Window Energy Rating are set out in the Glass and Glazing Federation’s Glazing Manual Data Sheet 2.3, Guide to the Calculation of Energy Ratings for Windows, Roof Windows and Doors. 10. No maximum U-value is set for display windows and similar glazing. There are no limits on the design of display windows and similar glazing, but for new buildings their impact must be taken into account in the calculation of primary energy and CO emissions. 2 11. In buildings with high internal heat gains, the average U-value for windows can be relaxed from the values given above if this can be shown to be an appropriate way of reducing overall CO emissions and primary energy. 2 However, values should be no higher than 2.7W/(m2·K). 12. 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. 13. 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 have a maximum U-value of 0.35W/m2·K. 14. For external fire doorsets, as defined in Appendix A of Approved Document B, Volume 2, in new and existing non- domestic buildings, a maximum U-value of 1.8W/(m2·K) is permissible. 25 Building Regulations 2010 Approved Document L Volume 2, 2021 edition O N L I N E V E R S I O N