Friday, March 7, 2008

Airtightness details


Having specified and designed a house to meet the AECB’s Silver Standard, airtightness plays a key role alongside high levels of insulation to achieve a low energy house. In our case we have followed the AECB’s Silver Standard construction details for timber frame buildings which advises the use of a continuous air/vapour control layer inside the building with all joints lapped, sealed and mechanically trapped.

This has probably been one of the most difficult aspects to achieve on site for our construction team which, in common with most UK builders, is simply not used to working to such a tight specification. With this in mind we opted for a solution which has largely avoided the need for specialist tapes and sealants, and in the main relies on the mechanical trapping of taped and lapped joints to provide a positive seal along with silicone sealant. We won’t really know how well this has worked until we do an airtightness test on the building, but on the basis that opening the front door feels somewhat akin to opening the door of a luxury car (ie. that air suction noise!) gives me some confidence. Also when it’s blowing a gale outside, there are no obvious draughts entering the building apart from the open trickle vents (shutters not yet fitted) and the yet to be connected stove flue.

1 comment:

PaulM said...

If you have a MHRV system, I can't understand why you'd have trickle vents in the windows - these defeat the air tightness strategies you've put in place and the MHRV provides all the fresh air you need.

Paul in Montreal.