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

R43 O N L I N E V E R S I O N c. Large extensions. If the building control body agrees that sealing off and testing the extension separately from the existing building is impractical, the extension should be treated as a large, complex building – see paragraph 7.5d. d. Large complex buildings. If pressure testing is impractical due to the size or complexity of the building, the developer may produce both of the following. i. A detailed justification of why pressure testing is impractical. ii. A detailed strategy to give confidence that a continuous air barrier will be achieved. It is reasonable for the building control body to accept this strategy in place of a pressure test to assess compliance. The developer should seek expert advice to confirm the justification and strategy in paragraph 7.5d. Any justification and strategy should be in line with the approved airtightness testing methodology, CIBSE’s TM23. It would not be reasonable to claim that air permeability better than 5.0m3/(h.m2) at 50Pa had been achieved. e. Compartmentalised buildings. If buildings are compartmentalised into self-contained units with no internal connections, it is reasonable for the building control body to accept a pressure test carried out on a representative area of the building as evidence of the building’s air permeability. If the area of the building fails the test, the criteria in paragraphs 7.1 and 7.6 apply, but the developer should also carry out a further test on another representative area to confirm that all parts of the building achieve the expected standard. Showing compliance and reporting pressure test results 7.6 The building primary energy rate and building emission rate calculated using the measured air permeability must not be higher than the target primary energy rate and target emission rate, respectively. 7.7 If the criteria in paragraphs 7.1 and 7.6 are not achieved, the building air permeability should be improved. New tests should be carried out until the building achieves the criteria in paragraphs 7.1 and 7.6. 7.8 The results of all pressure tests on buildings, including any test failures, should be reported to the building control body. Air pressure testing procedure 7.9 Air pressure tests should be performed following the guidance in the approved airtightness testing methodology, CIBSE’s TM23. The procedures in that document have been approved by the Secretary of State. 58 Approved Document L Volume 2, 2021 edition Building Regulations 2010 O N L I N E V E R S I O N