Mon, 25 May 2026 13:50:26 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286264#Comment_286264 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286264#Comment_286264 Tue, 12 Jan 2021 18:08:59 +0000 modernvictorian https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286272#Comment_286272 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286272#Comment_286272 Wed, 13 Jan 2021 08:07:30 +0000 GreenPaddy https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286273#Comment_286273 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286273#Comment_286273 Wed, 13 Jan 2021 10:08:52 +0000 modernvictorian https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286286#Comment_286286 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286286#Comment_286286 Wed, 13 Jan 2021 12:19:28 +0000 djh Posted By: modernvictorianThe builder wants to drape the membrane between rafters rather than cut individual strips. The Proclima website shows only the individual strips method. Is there any issue with wrapping the rafters in membrane? Perhaps water pooling in the troughs i.e. under the rafters?

https://www.proclima.com/products/external-sealing/solitex-mento-3000/application-guide/photo-gallery-retrofitting-underlay-from-the-inside-4597
Thanks for the link. I don't understand what the builder is proposing? Draping rather than cutting implied to me that you/he has access from the top to fit the membrane, but the link is discussing installing from underneath so I don't understand what your situation is or what the builder was proposing?

I note also that the application guide clearly says "The membranes are to be installed as an underlay or sarking membrane horizontally (parallel to the eave) in a taut manner with no sagging." So any idea of draping is presumably a non-starter.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286294#Comment_286294 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286294#Comment_286294 Wed, 13 Jan 2021 13:17:10 +0000 modernvictorian
Its not ideal but I think it might work as long as they cut the sections under the rafters with a Stanley knife as GreenPaddy suggested.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286316#Comment_286316 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286316#Comment_286316 Wed, 13 Jan 2021 16:01:01 +0000 djh Posted By: modernvictorianUsing staples to secure it to the side of the rafters.
The instructions say to use battens, not staples. i.e. full support that might be vaguely watertight or draught-tight.

Note that some of what the instructions say about using specific methods and products might not matter to you. They did matter to me since I now have a 25-year warranty on the roof structure courtesy of Pro Clima.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286334#Comment_286334 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286334#Comment_286334 Wed, 13 Jan 2021 19:12:14 +0000 Mike1 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286341#Comment_286341 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286341#Comment_286341 Wed, 13 Jan 2021 20:35:33 +0000 modernvictorian https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286346#Comment_286346 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286346#Comment_286346 Thu, 14 Jan 2021 09:41:40 +0000 lineweight
So it seems it would be possible to follow the guidance that it's installed "taut".

I've not seen this approach before; I wonder why they recommend it. Is it because you can't do a visual check from outside that the valleys are still there, after pushing insulation in? Or maybe it improves the airtightness/draught-proofness at laps between runs.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286354#Comment_286354 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286354#Comment_286354 Thu, 14 Jan 2021 10:48:31 +0000 modernvictorian https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286359#Comment_286359 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286359#Comment_286359 Thu, 14 Jan 2021 11:21:51 +0000 djh Posted By: lineweightI wonder why they recommend it.
Possibly the membrane won't stand up to the extra movement it will suffer if it is draped - billowing in the wind and so forth. They don't just recommend it, they say 'are to be installed .. in a taut manner with no sagging'. That's a pretty black and white instruction.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286364#Comment_286364 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286364#Comment_286364 Thu, 14 Jan 2021 11:58:20 +0000 lineweight Posted By: modernvictorianYes that is the ideal method. I can' t install the batten to make the valleys unfortunately as I would lose the specified depth of insulation and the U-value would then be out. Its not ideal but hopefully better than nothing in terms of at least keeping the wind away from the insulation. If water does come in it will run down into the woodfibre batts which hopefully can then dry out again at the next opportunity.

Isn't the other purpose of the batten to ensure there is a sufficient ventilation gap between the membrane and the underside of the tiles?

I would be wary of sacrificing that in order to get the "specified depth of insulation". It seems like the tail wagging the dog.

I don't see what you mean about water coming in - if it gets in, it should be running on top of the membrane and not getting into the batts at all. The batts are under the membrane aren't they?

The danger is water pooling against the tiling battens, instead of running underneath them.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286367#Comment_286367 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286367#Comment_286367 Thu, 14 Jan 2021 12:05:25 +0000 modernvictorian
Without creating the valleys (requiring an additional 25mm which I don't have...) I guess there is more risk of water running down the sides of the rafters and escaping through the edge of the membrane. Not sure a watetight seal against wood is possible.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286371#Comment_286371 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286371#Comment_286371 Thu, 14 Jan 2021 13:13:42 +0000 lineweight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286376#Comment_286376 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286376#Comment_286376 Thu, 14 Jan 2021 14:19:06 +0000 modernvictorian https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286377#Comment_286377 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286377#Comment_286377 Thu, 14 Jan 2021 14:39:32 +0000 lineweight https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286378#Comment_286378 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286378#Comment_286378 Thu, 14 Jan 2021 14:41:47 +0000 kebl2825 Posted By: modernvictorian... I guess there is more risk of water running down the sides of the rafters and escaping through the edge of the membrane. Not sure a watetight seal against wood is possible.

A detail I've seen mentioned on the forums before (I think on a suspended timber floor insulation thread?) is a glue/sealant line between the rafter and the membrane before mechanically fixing the batten from the other side of the membrane as a belt-and-braces seal. Just needs to be something that plays nicely with both the proclima solitex and the timber and should help confidence in it being watertight once cured.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286382#Comment_286382 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16432&Focus=286382#Comment_286382 Thu, 14 Jan 2021 15:02:25 +0000 djh