Now.

Since April 2002 the Building Regulations (England and Wales) Approved Document Part L2 required all new non-domestic buildings with a gross floor area of > 1,000 m2 to be tested for air permeability.

Since September 2003 the current requirement is that the air permeability (as measured by a fan pressurisation test) be < 10 m3/hr per m2 of envelope area at a reference pressure of 50 Pa.

Some clients, or even system manufacturers, require a much lower air permeability value than this for their buildings.

Future.

More stringent air permeability targets for new buildings are likely in the current revision process (for 2005) of AD L2. Also, different air permeability targets for different types of buildings may apply.

Also, the floor area threshold (currently 1,000 m2) may be significantly reduced. This will mean many smaller commercial buildings will require testing.

AD L1 (dwellings) may also include a requirement for testing. At the moment testing is optional.