1. All new dwellings (based on a sampling rate)
2. All new buildings other than dwellings
3. ‘Large’ Extensions to buildings other than dwellings

There are some exceptions to the above where buildings may be able to assume a poorer air permeability rather than undertake a test. The exceptions are explained below

1. Dwellings

Approved Document L1A - Conservation of Fuel & Power (for England & Wales) requires air tightness testing of new houses and flats to achieve building control approval.

Refurbishments of and extensions to existing residential buildings do not require testing.

Small developments (1 or 2 houses) may avoid the need to test by accepting an assumed poor value for air permeability of 15m³/h/m² but this may add costs to other aspects of the building specification in order that the building meets overall targets for emissions. Alternatively it may be possible to re-use existing test evidence where building designs have been repeated within 12 months of conducting the original test.

2. Buildings other than dwellings

Approved Document L2A - Conservation of Fuel & Power (for England & Wales) requires air tightness testing of new commercial buildings to achieve building control approval.

‘Small’ commercial buildings (with a floor area less than 500m²) may avoid the need to test by accepting an assumed poor value for air permeability (15m³/h/m²) but this may add costs to other aspects of the building specification in order that the building meets overall targets for emissions.

3. ‘Large’ extensions to buildings other than dwellings

Approved Document L2B - Conservation of Fuel & Power (for England & Wales) requires air tightness testing of ‘large’ extensions to commercial buildings to achieve building control approval.

‘Large’ is defined as greater than 100m² AND greater than 25% of the useful floor area of the existing building

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