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 4.11 Thermal bridging should be addressed in the design and construction of a building by either of the following means. a. Using construction joint details calculated by a person with suitable expertise and experience, which can then be used in the building primary energy rate and building emission rate calculations. Construction joint details should be calculated using both of the following. i. The guidance set out in the Building Research Establishment’s BR 497. ii. A process flow sequence that has been provided to the building control body indicating the way in which the detail should be constructed. NOTE: Evidence of suitable expertise and experience for calculating linear thermal transmittance would be to demonstrate that the person has been trained in the software used to carry out the calculation, has applied that model to the example calculations in the Building Research Establishment’s BR 497 and has achieved results within the stated tolerances. b. Using construction joints with no specific quantification of the thermal bridge values. In such cases, the generic linear thermal bridge values given in the Building Research Establishment’s Information Paper 1/06 and increased by 0.04W/(m·K) or 50%, whichever is greater, should be used in the building primary energy rate and building emission rate calculation. 4.12 To calculate linear thermal transmittances and temperature factors in support of the approaches in paragraph 4.11a, follow the guidance in the Building Research Establishment’s BR 497. Specified construction details should achieve a temperature factor that is no worse than the performance set out in the Building Research Establishment’s Information Paper 1/06. 4.13 To support the approaches in paragraph 4.11a, it should be demonstrated to the building control body that an appropriate system of site inspection is in place to give confidence that the construction procedures achieve the required standards. 4.14 When thermal elements are replaced or renovated, a report should be produced, signed by a suitably qualified person, which confirms all of the following. a. Appropriate design details and building techniques have been specified. b. The specified details, as constructed, provide adequate protection against surface condensation using the guidance in the Building Research Establishment’s Information Paper 1/06 and BR 497. Airtightness in existing buildings 4.15 When carrying out work in existing buildings, care sh ould be taken to reduce unwanted heat loss through air infiltration by doing all of the following. a. When installing pipework or services, taping and sealing around openings and service penetrations. b. When installing or renovating thermal elements, the element being installed should be draught- proofed and air-leakage gaps should be filled. c. When installing controlled fittings, the controlled fitting should be well fitted and reasonably draught-proof. NOTE: Particular attention should be paid to guidance in Approved Document F and Approved Document J when making an existing building more airtight. 28 Approved Document L Volume 2, 2021 edition Building Regulations 2010 O N L I N E V E R S I O N