Green Building Forum - Installing new windows before EWI on cavity wall Tue, 19 Dec 2023 07:07:19 +0000 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Installing new windows before EWI on cavity wall http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=300894#Comment_300894 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=300894#Comment_300894 Wed, 22 Mar 2023 14:37:35 +0000 cc64
I appreciate your many contributions here. They've done much to push back my ignorance.

I like this 95x35mm outer, 35x35mm frame approach.
I'm concerned about the weight this frame assembly has to bear, though - one of my windows comes in at 85kg. I'd like for this to stay where I want it, not doing a gravity-assisted overwhelm of the picture frame assembly.

Hence question what are you constructing your frame from? Compact foam would seem pricey. Otherwise what grade of construction timber? Something else?

And is the frame the same all around, even at the cill carrying the lion's share of window weight? There's only a 35mm surface to interface with the (not entirely perfect) brickwork; are you using any bonding here to augment the screws mentioned?

(Paranoid about free falling windows)

Thanks]]> Installing new windows before EWI on cavity wall http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=300902#Comment_300902 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=300902#Comment_300902 Wed, 22 Mar 2023 16:26:59 +0000 fostertom
Just looking at the section drawing above, the 'picture frame' does look unstable, liable to tilt under load - but don't forget it's strongly braced to the abutting ditto at the corners, so can't tilt, except yes maybe by twist/sagging towards centre of a long cill - so perhaps a short block of same vertically, similarly on-edge, screwed to wall to stop it sagging. The 35x35s also glued and screwed add stiffness and twist resistance.

Why are we whispereing? I don't mind editing to make this public?]]> Installing new windows before EWI on cavity wall http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=300913#Comment_300913 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=300913#Comment_300913 Thu, 23 Mar 2023 09:26:23 +0000 fostertom
Not sure about the exact long screws but well available, surely?]]> Installing new windows before EWI on cavity wall http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=302747#Comment_302747 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=302747#Comment_302747 Sun, 06 Aug 2023 11:47:38 +0100 cc64
from the drawing shown this picture frame approach leaves ~1/3 of the frame depth exposed to the elements.

How would you suggest protecting this arrangement from the elements, particularly at the top of windows not directly under the eaves (the OP asked about the practicalities of getting an installation before EWI though winter)

ta]]> Installing new windows before EWI on cavity wall http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=302755#Comment_302755 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=302755#Comment_302755 Sun, 06 Aug 2023 16:17:32 +0100 djh
Posted By: cc64at the cill carrying the lion's share of window weight
There's no reason for the sill to carry the window's weight - if it is screwed to the supports through its sides, then those vertical supports carry most of the weight.
How would you suggest protecting this arrangement from the elements, particularly at the top of windows not directly under the eaves
Depends on whether aesthetics are important or not. If not then we protected an exposed construction similar to this over winter with a piece of DPM taped to the top (using Sicrall tape). It lasted fine for the six months or so it was exposed, and could have been redone at any time to extend the length of exposure if necessary.

If aesthetics are important then some painted board or other screwed or [removably] glued in place. Board could be exterior plywood or plastic sheet or some cement board or whatever.]]> Installing new windows before EWI on cavity wall http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=303016#Comment_303016 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=303016#Comment_303016 Tue, 29 Aug 2023 10:43:20 +0100 GreenApprentice
What I’m not sure about is the DPM. This is currently wedged between the outer brick leaf and the closed cavity in the reveal. We will clear the closed cavity to remove thermal bridging, but am not sure what to do about the DPM. I suspect that we should remove the old DPM? Do we need to add new DPM somewhere in our new window install or is this taken care of with all the weatherproofing and airtighting products? We’re going to make the outside of the window weathertight and vapour open and make the inside of the window airtight.]]> Installing new windows before EWI on cavity wall http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=303019#Comment_303019 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=303019#Comment_303019 Tue, 29 Aug 2023 16:03:14 +0100 tony
Ideally a bit of the real new window frame would have the reveal plaster onto it

Maximise rather than minimise glass area]]> Installing new windows before EWI on cavity wall http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=303020#Comment_303020 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=303020#Comment_303020 Tue, 29 Aug 2023 18:13:59 +0100 Peter_in_Hungary Posted By: tonyI would make the new windows wider than the opening then fix through the frame or frame extension into the old outer skin.

Ideally a bit of the real new window frame would have the reveal plaster onto it
With caution if you have inward opening tilt and turn lights]]> Installing new windows before EWI on cavity wall http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=303021#Comment_303021 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=303021#Comment_303021 Tue, 29 Aug 2023 18:23:39 +0100 tony Installing new windows before EWI on cavity wall http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=303046#Comment_303046 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=303046#Comment_303046 Thu, 31 Aug 2023 08:24:55 +0100 GreenApprentice
Any thoughts on the DPM?]]> Installing new windows before EWI on cavity wall http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=303052#Comment_303052 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=303052#Comment_303052 Thu, 31 Aug 2023 17:49:00 +0100 tony
Certainly no need with EWI]]> Installing new windows before EWI on cavity wall http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=303054#Comment_303054 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17578&Focus=303054#Comment_303054 Thu, 31 Aug 2023 19:49:31 +0100 GreenApprentice