Unravelling airtightness

With the application of part L2 of the Building Regulations in the UK, new buildings with excessive air leakage have no longer been acceptable. All new commercial and public building over 1000 m2 must be tested for airtightness. An air permeability formula measures the envelope of walls, roof and ground floor area. This paper explains why bother about air leakage, and what desginers and constructors must do, and how the testing for airtightness should be carried out. The essential message is : build tight - ventilate right.