Green Building Forum - Would you prefer foil backed plasterboard or a continuous vapour/air barrier? Fri, 07 Aug 2026 20:38:25 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61882#Comment_61882 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61882#Comment_61882 Thu, 10 Sep 2009 13:17:04 +0100 tony
I definitely prefer a vapour barrier which doubles as an air barrier and is continuous.

Any other opinions?]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61889#Comment_61889 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61889#Comment_61889 Thu, 10 Sep 2009 14:12:28 +0100 Timber
Timber]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61896#Comment_61896 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61896#Comment_61896 Thu, 10 Sep 2009 16:01:52 +0100 fostertom Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61904#Comment_61904 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61904#Comment_61904 Thu, 10 Sep 2009 17:38:19 +0100 Johan
Tony, what are you using in your masonary build?

Tom,

That depends how you join it. If you use double sided vulcanising tape with polythene and then squeeze it with a batten on top it won't leak in the joints for sure! There are other places for it to leak though I agree and a brethable wall might be a better option for a good indoor environment. :bigsmile:]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61905#Comment_61905 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61905#Comment_61905 Thu, 10 Sep 2009 18:08:52 +0100 fostertom Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61908#Comment_61908 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61908#Comment_61908 Thu, 10 Sep 2009 18:42:04 +0100 tony
how do you join up the sheets or dont you?]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61910#Comment_61910 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61910#Comment_61910 Thu, 10 Sep 2009 20:55:52 +0100 jamesingram Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61913#Comment_61913 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61913#Comment_61913 Thu, 10 Sep 2009 21:51:30 +0100 tony Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61919#Comment_61919 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61919#Comment_61919 Thu, 10 Sep 2009 23:03:32 +0100 fostertom Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61925#Comment_61925 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61925#Comment_61925 Fri, 11 Sep 2009 09:22:52 +0100 Timber
There is no such thing as a vapour barrier. You will never get a full barrier to the passage of moisture vapour. You ONLY need to control it. hence it is called a vapour control layer. The term barrier should not be used.


As for punchers, so what? a SMALL puncher in a vcl will not cause a problem. with a timber frame wall, moisture vapour that does get into the wall will be able to dissapate.

If there is a large hole or rip is a different matter, but there are many many ways to mitigate against that happening.

As for breathable constructions, well whatever floats your boat. But even breathable walls have a vapour control layer! Its just not polythene.


Timber]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61926#Comment_61926 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61926#Comment_61926 Fri, 11 Sep 2009 09:37:07 +0100 Johan in):

1. External cladding (E.g. OSB/Panelvent/woodfibre board)
1. Vertical 38x89 with insulation between studs
2. Horisontal 38x89 with insulation between studs
3. Vapour barrier
4. Vertical 47x47 with insulation between studs
5. Internal cladding (E.g. Plasterbord/OSB/Prticleboard/timber)

You'll have a 47mm cavity for your wiring and any screws in the walls, making puncturing a substantially smaller issue. (You'll also have 230mm of insualtion and pretty much eliminate any cold bridges, but that's a different story...)

How you solve this in a masonary construction I don't know. I was hoping Tony would have some suggestions! :)

Posted By: fostertomAs I see it, a continuously clamped membrane joint doesn't need tape anyway - but a real challenge to make really continuous. And then there's still the rest of it, a magnet for punctures, whether looking short-term, or over a lifetime!
Clamping is good. However if you're trying to achieve a very high level of air tightness you should seal the joints properly.]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61929#Comment_61929 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61929#Comment_61929 Fri, 11 Sep 2009 10:43:22 +0100 Tuna
That is, if your structure is inherently airtight (eg. SIPs, Hempcrete, ICF or any of the continuous material construction techniques), then with MHRV the internal moisture levels should be maintained at a level where a vapour barrier is not necessary? I'm imagining the structure constantly 'breathing out' the moisture ingress rather than physically blocking it's path.

This is an area where I struggle to understand the different advice and practices, particularly where what works with one construction technique appears to be completely counter to standard practice in another.]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61931#Comment_61931 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61931#Comment_61931 Fri, 11 Sep 2009 11:24:10 +0100 Timber
Timber]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61933#Comment_61933 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=61933#Comment_61933 Fri, 11 Sep 2009 13:37:12 +0100 tony
No this is certainly not true

Indoor humidity levels will generally be higher than out door levels especially in the colder months -- even with MHVR. Severe problems will arise with timber construction where moisture condenses within the structure or insulation if there is nothing to stop it this will cause mould. rot and disasters.]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=289957#Comment_289957 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=289957#Comment_289957 Wed, 09 Jun 2021 09:09:26 +0100 Victorianeco
The asbestos removal company has essentially stripped it back to brick....]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=289958#Comment_289958 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=289958#Comment_289958 Wed, 09 Jun 2021 09:26:50 +0100 revor https://www.british-gypsum.com/products/gyproc-thermaline-pir?tab0=0]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=289959#Comment_289959 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=289959#Comment_289959 Wed, 09 Jun 2021 10:15:39 +0100 WillInAberdeen
In Scotland it requires U=0.22 for 'alterations' to existing walls, such as re-lining, so you need to add about 100mm thickness of PIR or 150mm of polystyrene. Higher standards apply for 'conversions' or newbuilds.

What are you planning to do for insulation - once you decide that, then the airtightness and vapour measures should become clear?

Could go on either the garage or the room side of the wall. Considerations about joining to any other wall/floor insulation that might be existing (or future).]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=289961#Comment_289961 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=289961#Comment_289961 Wed, 09 Jun 2021 10:53:38 +0100 djh Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=289963#Comment_289963 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=289963#Comment_289963 Wed, 09 Jun 2021 13:19:39 +0100 fostertom Posted By: fostertom'breatheable wall' rule-of-thumb, where inboard resistance should be five times outboard]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=289964#Comment_289964 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=289964#Comment_289964 Wed, 09 Jun 2021 13:23:22 +0100 tony Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=290106#Comment_290106 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=290106#Comment_290106 Fri, 18 Jun 2021 18:01:07 +0100 jms452 Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=290110#Comment_290110 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=290110#Comment_290110 Fri, 18 Jun 2021 20:00:29 +0100 djh
Ignoring the 'what about the insulation?' elephant in the room.]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=296223#Comment_296223 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=296223#Comment_296223 Sun, 22 May 2022 20:31:17 +0100 steveroofer Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=296225#Comment_296225 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=296225#Comment_296225 Sun, 22 May 2022 20:46:05 +0100 tony
I only ever used polythene as a vapour barrier, doesn’t need to expensive on my ceilings I did use cheap dpm poly.]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=296229#Comment_296229 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=296229#Comment_296229 Sun, 22 May 2022 21:38:40 +0100 djh Posted By: steverooferAs a roofer I only ever do warm roofs with a vapour barrier so to do a internal vapour barrier and also to do the walls was completely new to me.I don't understand this. I don't think the type of roof makes any difference to the difficulty or otherwise and I thought a warm roof removed the necessity for a vapour barrier in theory at least (although not for an airtightness layer of course.

Airtightness barriers are absolutely essential IMHO. Vapour barriers generally involve the same amount of work, so I don't understand why they would be considered especially difficult. How expensive they are depends on the precise specification. Intello Plus vs polythene vs render/plaster vs blowerproof vs whatever.]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=296230#Comment_296230 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=296230#Comment_296230 Mon, 23 May 2022 02:32:30 +0100 Mike1 Posted By: djhAirtightness barriers are absolutely essential IMHO
Yes, hopefully we all agree on that, but here's a video clip I shot at the weekend to illustrate why! Don't think the glassfibre insulation is doing much good...]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=296232#Comment_296232 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=296232#Comment_296232 Mon, 23 May 2022 08:20:58 +0100 Peter_in_Hungary Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=296234#Comment_296234 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=296234#Comment_296234 Mon, 23 May 2022 10:54:48 +0100 Mike1 Posted By: Peter_in_Hungarywhat is the context of the video? What is the make up of the wall allowing such a gale?It's a mansard roof; zinc cladding on timber, 75mm glassfibre, plasterboard - and evidently no airtight barrier. I'll be redoing it later in the year.]]> Would you prefer foil backed plasterboard or a continuous vapour/air barrier? https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=296239#Comment_296239 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=4536&Focus=296239#Comment_296239 Mon, 23 May 2022 17:28:54 +0100 tony