Tue, 19 Dec 2023 06:44:24 +0000 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293785#Comment_293785 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293785#Comment_293785 Thu, 16 Dec 2021 16:46:31 +0000 Shevek
We've specified 220 mm i-joist rafters fully filled with glass mineral wool (with 0.032 thermal conductivity) and an Intello Plus VCL to underside of rafters (with a further 25 mm batten/service zone + plasterboard)

But there are currently very long lead times for the glass mineral wool (estimated delivery March 2022), so the contractor wants to look at alternatives. One of which is a multi-foil honey comb product called Hybris between rafters and a thin multi-foil VCL (HControl Hydbrid) to underside of rafters.

HControl Hybrid + 170 mm Hybris is said to provide 0.13 u-value, and at roughly £26m2 considerably cheaper than mineral wool. And with a lead time of only 2-3 weeks. They also come with a suite of LABC certified details.
https://www.insulation-actis.com/pitched-roof.html

So, if those figures are correct, the advantages are obvious. What are the other things to consider? I'm going to list them here as people post them:]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293791#Comment_293791 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293791#Comment_293791 Thu, 16 Dec 2021 20:05:42 +0000 bhommels Not sure what the Hybris needs, it says something about high performance air gaps in the data sheet but what that means needs clarification. Perhaps installation instructions for both products can tell you more on how exactly the quoted U value is achieved. It might be very difficult to replicate in a practical setting.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293792#Comment_293792 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293792#Comment_293792 Fri, 17 Dec 2021 08:07:34 +0000 GreenPaddy
As to multi foils, I had a quick look at the hybris product previously, and it is not the same as the usual thin multifoils - often 15-20 mm thick, so very reliant on outer face conditions. This hybris looks more like a wool type insulation, in that it has considerable thickness, and so likely is more dependent upon air pockets in the 170mm thickness, meaning it shouldn't be squashed. That's much the same for wools.

Could you not go for 210mm of the hybris, so all insulation is between the rafters, as you had planned with the original wool. That keeps your design detailing the same, just a like for like replacement (Hybris shows lambda of 0.033 W/mK). No concerns then with thin multifoil of the Hcontrol additional surface layer?

Your Uvalvue will be better than that calc'd on the Hybris website, as your timber I beams will give significantly better thermal values. On that point, your insulation will need to be a bit wider, as your rafter thickness will be 9mm not the usual 45. Check that the Hybris can still expand to fill the 590mm gap, rather than the usual 555mm gap - it could be slack, and so not prevent air by-pass at the rafter interface?]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293795#Comment_293795 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293795#Comment_293795 Fri, 17 Dec 2021 09:33:41 +0000 Shevek http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293796#Comment_293796 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293796#Comment_293796 Fri, 17 Dec 2021 12:30:04 +0000 Shevek
The Intello Plus VCL allows for radiative summer back drying, providing extra protection to that the top layer of OSB, but might the Hybris insulation layer interfere with this process?]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293797#Comment_293797 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293797#Comment_293797 Fri, 17 Dec 2021 16:41:11 +0000 djh Posted By: Shevekextra protection to that the top layer of OSB
Sorry, I can guess but perhaps it would be better if you explained your buildup since this is the first mention of OSB?]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293798#Comment_293798 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293798#Comment_293798 Fri, 17 Dec 2021 16:51:15 +0000 Pile-o-Stone
We used a multifoil that is combined with a waterproof breather membrane (TLX Gold) on the upper (tile-facing) side of out roof, with Celotex PIR between and under the rafters.

It would be interesting if multifoils on their own are now OK for building control.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293800#Comment_293800 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293800#Comment_293800 Fri, 17 Dec 2021 18:06:47 +0000 djh http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293825#Comment_293825 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293825#Comment_293825 Sun, 19 Dec 2021 01:36:38 +0000 HollyBush
Recommended (by supplier) Tape to stick the thing together was poor at sticking - bought a different tape in the end.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293831#Comment_293831 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293831#Comment_293831 Mon, 20 Dec 2021 10:23:29 +0000 Shevek
My concern would be that the introduction of a non-breathable insulation like Hybris would interfere with that summer back drying process, slowing down the roof structure's ability to get rid of moisture.

- Plain clay roof tiles
- 25 mm softwood tile battens
- 11 mm softwood counter battens
- Pro Clima Solitex Plus breather membrane
- 18 mm OSB/3
- 220 mm Metsä Wood Finnjoists i-joists at 600 centres, with Knauf Rafter Roll 32 in between (3x 75 mm)
- Pro Clima Intello Plus vapour control layer
-25 mm softwood batten/service zone
-12.5 mm plasterboard]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293847#Comment_293847 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293847#Comment_293847 Tue, 21 Dec 2021 11:42:28 +0000 GreenPaddy http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293861#Comment_293861 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293861#Comment_293861 Tue, 21 Dec 2021 17:56:13 +0000 Shevek http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293938#Comment_293938 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293938#Comment_293938 Thu, 30 Dec 2021 16:34:36 +0000 djh

The James Webb space telescope uses a 5-layer multi-foil for its sunscreen and achieves a 300 K difference between front and back. The key of course is high vacuum on both surfaces and between all the foils ]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293946#Comment_293946 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17328&Focus=293946#Comment_293946 Fri, 31 Dec 2021 07:21:38 +0000 Jonti Posted By: djhThere's an excellent example of the proper use of multi-foil in the news at the moment.http:///newforum/extensions/Vanillacons/smilies/standard/bigsmile.gif" alt="" title="" >

The James Webb space telescope uses a 5-layer multi-foil for its sunscreen and achieves a 300 K difference between front and back. The key of course is high vacuum on both surfaces and between all the foilshttp:///newforum/extensions/Vanillacons/smilies/standard/devil.gif" alt="" title="" >

With each layer thinner than a human hair can you image the state it would be in after the builders had installed it ]]>