Tue, 19 Dec 2023 07:06:43 +0000 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303460#Comment_303460 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303460#Comment_303460 Thu, 21 Sep 2023 17:06:22 +0100 blubb
I am looking to retrofit EWI to a 1927 solid wall brick house. I am a little bit puzzled:

- One company is suggesting to use Kingspan K5 boards [1], which are rated for outside he claims. The downside here is that K5 only comes in thicknesses up to 70 mm.

- Another company is planning to use Kingspan K103 boards [2], which are rated "water-repellent" but classed as floor boards. The upside here is that these boards come in larger thickness.

The first company with a better overall package is refusing to install K103 and insist on K5.

I should add that the insulation will go under Weber silicone-based render.

Opinions?

Many thanks!

[1] https://ewistore.co.uk/shop/external-wall-insulation/k5-kingspan-external-wall-insulation-board-0-72m%C2%B2/?attribute_pa_size=60mm&mh_matchtype=&mh_keyword=&mh_adgroupid=&mh_network=x

[2] https://www.insulationexpress.co.uk/k103-100mm]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303461#Comment_303461 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303461#Comment_303461 Thu, 21 Sep 2023 17:41:11 +0100 lineweight
Seeing as Kingspan advertise K5 as being suitable for EWI, and don't advertise K103 as being suitable for EWI, I would be more comfortable with a system that uses K5.

Maybe the company proposing the K103 would be able to persuade me it's fine - I would simply ask them - why are they proposing a material that isn't advertised for that application by the manufacturer.

Ideally, I'd be looking for someone proposing a "system" (that is, the combination of external render, the various layers behind it including the insulation, and the fixings) that is recommended by one of the larger scale manufacturers, whether that's an insulation company or a render company. In the ideal ideal world there'd be a BBA certificate that described the whole system, what its limitations and appropriate applications are, and described what's important about the way it's installed.

Sometimes a "system" like this won't actually specify a particular insulation product, it might just say what type it needs to be, and then you can check whether whatever's being proposed satisfies that.

It kind of depends how deeply you want to get involved in choosing and specifying things. I would say that depending on exactly how the insulation installers are presenting themselves to you, they are effectively the designers of the installation so in theory if it all goes wrong it's their problem, but of course generally one wants to minimise the risk of that happening. That's why I'd be more confortable with them installing materials that I can see are clearly intended for the job.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303462#Comment_303462 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303462#Comment_303462 Thu, 21 Sep 2023 17:42:00 +0100 lineweight http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303475#Comment_303475 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303475#Comment_303475 Fri, 22 Sep 2023 08:17:47 +0100 Peter_in_Hungary http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303478#Comment_303478 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303478#Comment_303478 Fri, 22 Sep 2023 08:43:17 +0100 tony http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303484#Comment_303484 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303484#Comment_303484 Fri, 22 Sep 2023 13:09:44 +0100 revor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303485#Comment_303485 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303485#Comment_303485 Fri, 22 Sep 2023 13:34:53 +0100 lineweight Posted By: revorI used 2x50mm alternating K5 but left a gap and put on cedar cladding. I did not want a render over it even though the extension in block is rendered but that has a cavity as well as insulation. We live in an exposed area and did not want any risk of damp penetration through render. The stone work that is covered by K5 has shown no damp ingress but there would be a chance if it had been rendered. Cavity separation from the weather has provided dry houses for about 100 years now and see no reason why not to continue with it. ( A bit longer actually my previous house built1898 had cavity walls). The internal of the stone is either left uncovered or lime plastered. For EWI I would always opt for a rain screen cladding any time. The Kingspan manual does show various options of rain screen. The K% plus rain screen should not be any thicker than an equivalent u value of EPS.

I don't quite follow this - was your worry that damp would penetrate the render, and then also penetrate through 100mm of PIR insulation?]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303486#Comment_303486 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303486#Comment_303486 Fri, 22 Sep 2023 14:16:21 +0100 blubb Posted By: Peter_in_HungaryOut of curiosity - why kingspan, which is not breathable rather than EPS which is (slightly) breathable and whilst thicker for an equivalent U value usually works out cheaper.

Good question! I looked at EPS and it comes out about the same price (since one will need a larger thickness to get the same U-value). The main driving factor are the space constraints as there is a passage between houses involved.

Is your worry that vapour will not be able to escape from the solid walls through the K5?

Or is it the condensation? (the dew point should be well within the K5 for UK temperatures)]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303487#Comment_303487 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303487#Comment_303487 Fri, 22 Sep 2023 17:02:38 +0100 Peter_in_Hungary Posted By: blubbIs your worry that vapour will not be able to escape from the solid walls through the K5?
Yes]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303490#Comment_303490 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303490#Comment_303490 Fri, 22 Sep 2023 21:41:53 +0100 djh Posted By: revorFor EWI I would always opt for a rain screen cladding any time.I think the choice depends entirely on location, including exposure. Our house has lime render exposed to the elements, rendered directly on to the notoriously damp prone straw. We haven't seen any signs of a problem so far. We do have the traditional good hat and pair of boots. i.e wide overhangs on the roof and 6" height above ground before the straw starts plus 2' of gravel border around the house. But we're in the East of England and I know of cases in more exposed locations where an external timber rain screen has had to be added because of driving rain. So horses for courses.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303495#Comment_303495 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303495#Comment_303495 Sat, 23 Sep 2023 09:20:27 +0100 revor Posted By: lineweightI don't quite follow this - was your worry that damp would penetrate the render, and then also penetrate through 100mm of PIR insulation?

Yes once the insulation gets damp it becomes ineffective. Our stone farmhouse had been cement rendered on the outside and also on the inside. When I hacked off the render you could see hairline cracks and beneath the stone was wet for quite big areas. Inside was very damp even though house has open chimney. The walls could not breathe. It could be argued that my EWI does not allow the wall to breathe. But it can on the inside. Does a wall need to breathe both ways? I think not. Besides the outside is protected from the weather one wall is exposed in a conservatory and act as a heat sink/thermal mass. When I was building our extension I went to see work of a proposed builder and he was going to blow in insulation into cavity on completion. I asked my BCO about this and he advised me to stay clear as although it was permitted to use he would not trust it particularly in an exposed area. He said to stick to a cavity barrier every time. In our area many houses have had damp problems from filling cavities under energy schemes and had to be taken out. A neighbour had cavities filled and one section of a wall had to be demolished and rebuilt. I am in N Wales and bear the brunt of the SW Atlantic driven weather As DJH states horses for courses.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303496#Comment_303496 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303496#Comment_303496 Sat, 23 Sep 2023 10:09:35 +0100 lineweight
Also, the type of render that goes onto EWI is not the same as cement render.

It's not surprising that cement render would have cracks and that somewhat porous stone underneath would soak up water. But I'd not extrapolate from that, that damp is going to get through the render and the insulation of an EWI system. If stonework were getting damp behind EWI it would most likely be because of something like a leak at an eaves detail. And if water is getting behind the insulation a rainscreen cladding isn't going to help. The water will remain trapped behind the insulation.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303497#Comment_303497 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17966&Focus=303497#Comment_303497 Sat, 23 Sep 2023 10:15:50 +0100 WillInAberdeen