Green Building Forum - Extend insulation on timber-frame parts of house Tue, 19 Dec 2023 08:39:05 +0000 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Extend insulation on timber-frame parts of house http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17741&Focus=300274#Comment_300274 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17741&Focus=300274#Comment_300274 Mon, 13 Feb 2023 15:36:49 +0000 minisaurus
When renovating, I'm considering increasing the insulation of the timber frame parts - i.e. remove timber panels, add new framework to increase insulation width, add insulation, and replace the timber panels.

The existing insulation on the timber parts is approx. 12cm thick.

I'm concerned that this may create/shift dewpoints in the timber frame, or even where timber meets concrete.

What do others think?]]> Extend insulation on timber-frame parts of house http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17741&Focus=300281#Comment_300281 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17741&Focus=300281#Comment_300281 Mon, 13 Feb 2023 20:21:38 +0000 djh Posted By: minisaurusplastic-bag (subsequently occasionally perforated) vapour barrier around the internal plasterboardIt'd likely be a good idea to go around and make sure as many of the perforations as possible are taped up.

Posted By: minisaurusremove timber panels, add new framework to increase insulation width, add insulation, and replace the timber panels. ...

... I'm concerned that this may create/shift dewpoints in the timber frame, or even where timber meets concrete.
Generally EWI moves the dewpoint inboard, so further away from external timber cladding. It warms up whatever's inside!

edit: sorry - that 'inboard' should read 'outward'. :cry:]]> Extend insulation on timber-frame parts of house http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17741&Focus=300285#Comment_300285 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17741&Focus=300285#Comment_300285 Tue, 14 Feb 2023 10:11:29 +0000 minisaurus
Re. dew point, I was thinking I might start getting it on the old/existing 12 cm deep timber frame parts, once they’re covered with the new insulation?]]> Extend insulation on timber-frame parts of house http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17741&Focus=300287#Comment_300287 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17741&Focus=300287#Comment_300287 Tue, 14 Feb 2023 16:03:48 +0000 djh Posted By: minisaurusRe. dew point, I was thinking I might start getting it on the old/existing 12 cm deep timber frame parts, once they’re covered with the new insulation?Sorry I made a silly mistake in my last post - I meant the dewpoint is moved OUTward. So you're even less likely to get condensation inboard of the EWI on existing materials.]]> Extend insulation on timber-frame parts of house http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17741&Focus=300288#Comment_300288 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17741&Focus=300288#Comment_300288 Tue, 14 Feb 2023 16:15:59 +0000 WillInAberdeen
Or alternatively with an air gap between the insulation and the cladding, maybe 50mm, with gaps at the top and bottom for air to circulate behind the cladding and carry away any moisture that finds its way in there. With this option you need to be careful that birds, mice, wasps, fires cannot get in the gap, there may be different building laws about this in your country.

In some countries there are problems with insulation and internal plastic barriers if it is warm and humid in the summer. I don't know much about your climate (sorry!) if this applies to you or not.]]> Extend insulation on timber-frame parts of house http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17741&Focus=300292#Comment_300292 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17741&Focus=300292#Comment_300292 Tue, 14 Feb 2023 19:29:46 +0000 minisaurus
Climate is Sweden; the praxis here is usually to leave an airgap between the insulation and cladding, preferably with some kind of insect and mouse net at the top and bottom, although quite often this seems to be missing ...]]> Extend insulation on timber-frame parts of house http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17741&Focus=300295#Comment_300295 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17741&Focus=300295#Comment_300295 Tue, 14 Feb 2023 21:16:03 +0000 djh Posted By: WillInAberdeenYou need the outside covering to be breathable, so that any moisture that finds its way in can escape, rather than be trapped in the colder outer regions of the wall. Eg with breathable paint on the timber cladding.Isn't it a case of it needs to be breathable iff it is breathable?

Since the EWI moves the dewpoint outward, everything inside it should be above the dewpoint so there's no condensation risk inboard of the insulation. So if there's water vapour at the inner surface of non-breathable EWI it will still be vapour and won't condense. As long as there is sufficient EWI.

Water coming from the outside should be resisted by the cladding and drainage plane. That's their main purpose in life. Certainly liquid water should be able to drain out.]]> Extend insulation on timber-frame parts of house http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17741&Focus=300297#Comment_300297 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17741&Focus=300297#Comment_300297 Tue, 14 Feb 2023 21:58:12 +0000 WillInAberdeen
However minisaurus is planning an airgap to allow the construction to breathe. So long as the new external insulation material is also moderately breathable then all will be ok. Snowy weather is particularly good for sucking moisture out of breathable walls, the cold air gets really dry.]]>