Pass or Fail?
To comply with the requirements of Part L:
- the measured air permeability must not be worse than the limit value of 10m3(h.m2) @50Pa; and
- the DER calculated using the measured air permeability is not worse than the TER
This means that if a design adopted a low design air permeability in order to achieve a performance better than the TER. It would not fail to comply with Part L if the pressure test achieved the limit value and the TER was achieved.
If the tested air permeability performance is unsatisfactory:
- Dwellings – the contractor will need to undertake remedial work and then commission a re-test on the same unit as well as an additional test on another unit. Testing and re-testing will continue until the tests prove that the performance is satisfactory.
- Non-dwellings – the contractor will need to undertake remedial work and commission a further test to confirm that the required performance is achieved.
2010 example:
- Four identical dwellings with a design air permeability of 6m3(h.m2) @50Pa are required to be tested
- Only two need to be tested, each achieve 4m3(h.m2) @50Pa; and 5m3(h.m2) @50Pa
- Although both pass, the assessed air permeability of the other two is 6.5m3(h.m2) @50Pa so they both fail.
- To get all dwellings to pass with only one additional test, it will need to achieve a result of no more than 3m3(h.m2) @50Pa in order to push the average down below 4m3(h.m2) @50Pa.
- It may be easier to test both remaining dwellings.
