Wall cavity / filling around new double glazing installation

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Hi all,

I'm having my double glazing fitted this week, and a big part of this job was to fix the crap installation done prior to this.

They have only been here for a day and obviously have to finish this off, but 2 questions that I can check with them tomorrow...

In the following 2 pics you can see the white insulation and general dirt in the cavity (the previous installers kindly chucked all the rubble down there which I have removed most of, but some still remains) and the installers tell me its not necessary to put any extra insulation down there. There's 10-20cm of depth that I could pack new insulation if it needs it, but I have the fibreglass insulation (yellow colour) as opposed to the flakey white stuff in there. Do I need to bother?

IMG_1584.jpg

IMG_1591.jpg


Secondly, I am getting the edges of the window frame re-plastered as loads fell apart when the old windows came out. In a few areas in between the brickwork and new installation there are gaps, (vertically up the wall) sealed from the outside by the new trim / sealant but from the inside does this need to be filled with expandable foam / similar? (And can this be done at this stage?) Obviously the plasterer can plaster up to the edge of the frame, but not inside it, as such.

IMG_1593.jpg

IMG_1595.jpg


Thanks :D
 
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You would be wise to fill the remaining cavity with insulation such as Celotex etc rather than having a void section. As for the window sides, expanding foam is perfect for filling the gaps but control the amount carefully as too much could bulge the silicone on the outside, you then trim it flush internally once set and then either have the reveals skimmed or fill and sand if not too bad before painting.
 
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there are a a lot of mortar chippings down that cavity. If you happen to have a workshop vac, it would be good to hoover them out to prevent damp tracking across.
 
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get as much rubble out as possible, it is bridging the gap between the outer and inner skin. This could allow damp to travel across.

Insulated as much possible.
 
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thanks guys, cleared rubble and put extra insulation down there. all sealed round the edges too.
 
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There are proper insulation products exactly for the purpose you require.

They are called "Cavity Closers" which incorporate a foam insulation which closes the cavity and inbuilt damp proof course..

Cavity-Closer_large.jpg


Regarding gap around the edge, I always use expanding foam around all windows and doors even if the gap is quite small.. due to its draft proofing and insulation properties... because i never fit windows tight into the gap, I make sure they have an gap of 5mm around the edge to allow for expansion and also so that the wall is not directly touching the window frame (because a wall directly touching a frame pulls the heat out the frame ... which means frame then soaks up more heat from the room leading to increased heat loss.)
 
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