Mon, 25 May 2026 13:09:21 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=146&Focus=1582#Comment_1582 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=146&Focus=1582#Comment_1582 Tue, 27 Mar 2007 20:20:54 +0100 Peter A But what about the upper floor void, how do you maintain the integrity of the vapour barrier or am I worrying unneccessarily, could really do with some advice from the Passivhaus/Canadian experts on air leakage.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=146&Focus=1621#Comment_1621 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=146&Focus=1621#Comment_1621 Wed, 28 Mar 2007 12:39:03 +0100 Paul in Montreal
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.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=146&Focus=1624#Comment_1624 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=146&Focus=1624#Comment_1624 Wed, 28 Mar 2007 13:05:12 +0100 Peter A https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=146&Focus=1633#Comment_1633 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=146&Focus=1633#Comment_1633 Wed, 28 Mar 2007 14:52:54 +0100 Guest 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.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=146&Focus=1641#Comment_1641 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=146&Focus=1641#Comment_1641 Wed, 28 Mar 2007 16:07:09 +0100 Johan
You can also have a vapour barrier in the ground floor ceiling (below the joists) and maybe in the first floor floor (above the joists). You can probably leave the first floor barrier out though as the natural airflow is upwards anyway.
That will stop any internally generated moisture from enterering the floor void. Paul's solutions is as good though. What ever is easiest for you!

Guest,

Sorry, but I disagree completely with that...

A vapour barrier in a wall is only good for stopping any vapour generated inside the building. However, with a well insulated, well ventilated house you get very little condesation anyway. A timber framed wall is always breathable on the outside...

In Sweden in the 70's it was very popular to use plastic paints on the outside walls (as it is in Britain currently...) as they were sold as maintenance free. 10 years later it showed out that it wasn't such a good idea as the timber cladding rotted away nicely...

There's no reason why you shouldn't use a vapour barrier in a house in UK.

btw, when ice melts it turns to water...]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=146&Focus=1672#Comment_1672 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=146&Focus=1672#Comment_1672 Thu, 29 Mar 2007 10:21:36 +0100 Peter A 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.]]>