Hi Peter,

leakage between floors is rather easily solved. In our new build, the join between the ground floor and first floor where the floor trusses meet the external frame were simply sealed with closed cell polyurethane foam that was applied before any other insulation or interior finishing was added. Closed cell polyurethane is a vapour barrier so there wasn't an issue here. Same thing was done at the rim joist (where the wooden framing sits on top of the concrete foundation). After the foam was applied, insulation was added to the wooden frame and then foil faced polyisocyanurate foam board was glued to the studs and sealed using acoustic sealant to the polyurethane foam. This polyiso layer also is a thermal bridge as 1x3 strapping was added on top of this and the interior gyproc then screwed to the strapping. Electrical outlets were encased in a vapour barrier which was then taped to the front of the polyiso boards using "tuck tape". The main air leakage barrier, of course, is external to the wooden frame and is also taped at all joints.

Hope this helps,

Paul.

Me thinks that a major problem looms on the scale of the New Zealand problem only very much bigger concerning vapour control layers inside timber walls. Some designers think that if they draw a line on a paper or screen and call it a vapour barrier that vapour will exist at on one side of this line and no vapour on the other side of this line. Not quite comprehending that a tiny hole such as made with a staple or a breakdown in seals or tape - which are almost 100% derived from petrochemicals and which have a limited life of average about 7 years before the adhesion gives out - will cause a build up of water molecules inside a timber frame wall with no venting. This is guaranteed to cause a problem just after the 10 year warranty expires.
Our climate which is similar to New Zealand is not suitable for timber frame unlike Scandinavian countries and Canada where most of the water is ice.

Posted By: GuestMe thinks that a major problem looms on the scale of the New Zealand problem only very much bigger concerning vapour control layers inside timber walls.

Oh dear I wonder what we will do with all the timber frame units built in the UK over the last 30-40 years! I have to say that I believe you are wrong and am in total agreement with Johan.

Johan thanks for your input, I wanted to avoid vapour barriers on ceilings if at all possible as they are prone to abuse on site with the number of service penetrations which would be difficult to police on large developments, want to get to a situation where the vapour barrier is in on the external frame, all services run, windows in, the vapour barrier can then be signed off before allowing boarding to occur. So really need to come up with a simple solution for the rim beam zone that still allows the timbers to breathe.