5. What do I need to look out for to minimise air leakage?
For houses and flats of standard construction, it is possible to achieve reasonable air tightness without having to use specialist products and techniques but it requires close control of trades whose work impacts on the air barrier, for example:
- Dry liners – to ensure there is a continuous ribbon of plaster at the foot of the boards
- Window/door fitters – external doors and windows are sealed around and create a good seal when closed
Plumbers – sealing around pipes and duct work
- Electricians – sealing around cabling
- Bathroom and kitchen fitters – ensuring pipe work is sealed where it penetrates the air barrier and/or there is continuity of sealants.
It is also important to have good attention to detail in the final finish e.g. mastic sealing, to ensure continuity is achieved especially in bathrooms and kitchens. This means the unit must be basically ready for occupation before being tested which creates an issue if the building/unit fails. When targeting a high level of air tightness (4 and under as a guide) then specialist membranes and tapes should be used to create a continuous air barrier within the construction detailing so that you are not relying on decorative finishes and mastic seals. For unusual constructions and/or commercial buildings, the air barrier tends to need much more careful consideration/design because it tends to be more complex to achieve continuity between the walls and the roof, there are more ‘hidden’ areas (suspended ceilings, raised floors, etc) and a greater number/scale of service penetrations (air-con, IT, fire sealing, etc). It is important to have an appreciation of the air barrier and therefore what jobs need to be completed when planning the air test.