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

L1(a) O N L I N E V E R S I O N Limiting standards for renovated and retained elements 4.7 Existing elements that are being renovated should meet the limiting standards in Table 4.2. Guidance on when an existing element should meet the standards in Table 4.2 is given in Section 11. Elements that should meet the standards include both of the following. a. Thermal elements being renovated in existing buildings. Renovated elements should achieve the U-values in Table 4.2, column (b). b. Elements being retained in existing buildings, for example following a material change of use or change to energy status (see Section 11). Retained elements with a U-value that is higher than the threshold value in Table 4.2, column (a), should be upgraded to achieve the U-values in Table 4.2, column (b). 4.8 If achieving the U-value in Table 4.2, column (b) either: a. is not technically or functionally feasible or b. would not achieve a simple payback of 15 years or less then the element should be upgraded to the lowest U-value that both: a. is technically and functionally feasible and b. can achieve a simple payback not exceeding 15 years. Generally, a thermal element once upgraded should not have a U-value greater than 0.7W/(m2·K). A lesser standard for the thermal element may be acceptable where work complies with Part C of the Building Regulations on protection from the harmful effects of interstitial and surface condensation. 26 Approved Document L Volume 2, 2021 edition Building Regulations 2010 O N L I N E V E R S I O N