Sun, 31 May 2026 04:08:58 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309350#Comment_309350 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309350#Comment_309350 Sun, 28 Sep 2025 08:47:48 +0100 Victorianeco
We are looking to add them to the EWI layer of our cavity wall property.

We are thinking:

- Remove 25mm of render all around the existing window opening
- Make the windows 20mm wider all around than the window opening
- Mount then externally with brackets
- Use compactfoam below window to support them horizontally?
- Then use air tightness tape around inside and outside the windows?
- Render outside using sand/cement
- Then EWI?

Is there a better detail than this?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309352#Comment_309352 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309352#Comment_309352 Sun, 28 Sep 2025 11:57:18 +0100 Peter_in_Hungary https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309354#Comment_309354 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309354#Comment_309354 Sun, 28 Sep 2025 17:38:05 +0100 Victorianeco https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309355#Comment_309355 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309355#Comment_309355 Sun, 28 Sep 2025 23:51:20 +0100 Peter_in_Hungary I've used brackets on the bottom and the sides and then the usual EPS up to the window.

Will the compact foam just spread the load onto the EPS which will then still be carrying the weight of the window? (Other than the side brackets which will be in sheer)]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309356#Comment_309356 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309356#Comment_309356 Mon, 29 Sep 2025 08:37:03 +0100 Victorianeco https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309357#Comment_309357 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309357#Comment_309357 Mon, 29 Sep 2025 09:56:13 +0100 Doubting_Thomas
https://www.21degrees.com/compacfoam/

See their photo below:

Not sure it will apply if you are retrofitting but perhaps you can cast something locally to counterbalance the weight of the windows?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309358#Comment_309358 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309358#Comment_309358 Mon, 29 Sep 2025 10:37:31 +0100 djh https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309373#Comment_309373 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309373#Comment_309373 Wed, 01 Oct 2025 08:42:49 +0100 fostertom
Trouble is, the modern trend to provide neither a technical design manual, nor any equivalent info online. Till the recent past, serious product manufacturers published everything, tho some better than others. "Request a brochure" isn't it. Now, and in Compactfoam's case, to get any further you have to "Request a quote" or Contact them - a sure prelude to listening to a load of sales chat. Life's too short.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309379#Comment_309379 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309379#Comment_309379 Wed, 01 Oct 2025 11:26:40 +0100 djh
https://odoo.21degrees.com/shop/compacfoam-74#attr=105
https://www.wiki-compacfoam.info/wiki/en:brandverhalten-von-compacfoam]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309387#Comment_309387 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309387#Comment_309387 Wed, 01 Oct 2025 12:58:21 +0100 fostertom
Straight off, a pic of Compactfoam similar to my use of chunky timbers lately, like 35x65 and 32x32, as 'picture frame' surround/mounting for window frames outboard in EWI (instead of flimsy ply 'picture frame' or metal brackets). If the timber's not too bad for that purpose at U1.0, Compactfoam's better at U0.54, tho still not matching the U0.38 of the EWI it's embedded in.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309452#Comment_309452 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309452#Comment_309452 Wed, 08 Oct 2025 12:39:34 +0100 wookey
As belt+braces I would use illbruck permanently flexible airtightness foam as well as tape (That's how internorm fitters did my windows, which are otherwise much like yours, but not oversized).

You can now get Almavert from Partel in Ireland which has very similar properties to compacfoam but is cheaper and is recycled PET rather than virgin polystyrene. I've not actually cheked the LCAs but I assume it's significantly better.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309455#Comment_309455 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18355&Focus=309455#Comment_309455 Wed, 08 Oct 2025 14:36:16 +0100 fostertom