What contractual behaviour is anticipated in a JCT-98 traditional situation, when a building fails its air tightness test, and there is no obvious answer to the 'why do these details leak?' question? If sections of the building have to be opened up to investigate the leaks, who will be paying? If the contractor decides that the designers are at fault for 'poor detailing', were they themselves under a duty to spot the 'poor detailing' during construction?
This is an interesting question and a bit of a grey area I'm afraid. The contractor is responsibe for organising the air tightness test and therefore responsible for the building passing this test. However, the contractor will follow details and designs provided to them by the design team, so really they are both responsible for ensuring the building is air tight and passes its test on completion.
At the moment it seems that the contractor foots the bill for the air tightness test and any subsequent investigative work and remedial sealing that may be necessary if the building fails.
Source
Building Sustainable Design
