Fixing gaps left by my builder in full fill cavity wall, around windows and doors

betterbuilt

I'm concerned about gaps between my newly installed window frames and the full fill cavity wall insulation of my new build. (Same issue around doorframes.) There are deep gaps between the frames and the wall insulation in places, in the corners, and the wall insulation surface in general is very unevenly cut.

My builder has used 150ml full fill cavity insulation in my new house build.

The windows and doors have been installed.

The next phase is to render the walls inside and out.

I have the following questions:

1. How small a gap is required to ensure proper insulation?

2. Is expanding foam sufficiently insulated a material to be used as a filler?

3. If not, is there an alternative filler, or method of filling, with sufficiently high insulation value to match the existing wall insulation, to make sure the window frames are packed tightly up against the wall insulation, if this is necessary to ensure proper insulation.

Many thanks if anyone has any ideas or information on this. My builder has not done a tidy job. I'm trying to make sure he fixes these snags as well as possible, to maximise insulation values.

BryanF

1. 0
2. Yes in conjunction (but thermal foam as opposed to gap filler foam, Hiliti do one ) and on the warm side - continous sealed air-tightness tape.
3. Yes, there are different products are on the market: PIRs, composite timber products etc, these have particular sizes that you measure out to suit before putting in the windows. This is detailed on an arch’s drawing that the builder follows. Now that the win straps are in, it may be too late for those options, can you foam to the back of the dpc, be careful not to dislodge or move it!. Be particular that every inch is foamed.infact I’d suggest you do it yourself. Ware gloves, and be very careful you have the right’thermal’ ‘low expansion’ foam

Wartburg

betterbuilt wrote: »

I'm concerned about gaps between my newly installed window frames and the full fill cavity wall insulation of my new build. (Same issue around doorframes.) There are deep gaps between the frames and the wall insulation in places, in the corners, and the wall insulation surface in general is very unevenly cut.

It´s more an advantage than disadvantage, you have at the moment.
Gaps between the window frame and the wall (insulation) are required for insulation purposes and to allow expansion/ movement. Watch out for B2 rated Gun Grade Foam or even better Air Tight Foam. The last one is a closed cell expanding foam which stays softer than basic foams. Please do not use the standard (B3 rated) foam, because most of them do not create a consistent foam layer.

betterbuilt

Thanks so much to both of you for your replies. Hugely helpful.

The pic of the foam that's been cut looks like a really neat job!

I've looked up some products - the best I've found so far are these two:

Hilti CS-F JS Joint sealing foam, thermal conductivity rating 0.0345

Prodomo Air Tight Gun Grade Foam, B2 rated, thermal conductivity rating 0.035

I'll definitely give it a go.

Massive thanks again.