DIY cavity wall insulation?

[WhiteChristmas]

Hello all, not sure if this is the best place to post this.

We are having three front windows replaced this week (two bays and a small bedroom). The bedroom bay has a tendency to gather condensation which in turn has caused mould issues in the past (currently resolved with a dehumidifier over the winter as no trickle vents). I'm assuming there is no insulation in this bay (or if indeed there is a cavity).

While the window is out, could I insulate the wall (and the other two for that matter - assuming there is none there already)?

Obviously I wouldn't want to hinder the window installation but to my (small and simple) mind this would be quick and easy job to do, am I correct in this assumption?

Other questions to consider:

* What would I use (ideally something from B&Q, etc since the windows are being done this week)?
* Would I have to insulate the whole wall (ie, just the bottom half)?
* What would the risks be?
* Am I being stupid even considering it and I should get a professional in to do the lot?

Please feel free to ridicule me but I would appreciate someone coming back with an answer.

Thanks

 

[regsmyth]

I would say it's a bit late to be thinking about this now, however, there's no reason why you can't do the work after the windows are fitted.

If you have a cavity, you won't be able to fit insulation into it properly through the window reveal when the old windows are taken out.
You would have to take the inner leaf down, or get it injected when the window fitters have finished.

If you don't have a cavity, you would need to build a supporting framework in which to fit your insulation against the inside face of your walls. Not very straightforward really, and extra work to make deeper window reveals.

You would only need to insulate the external walls. But you have to take a lot of care to make sure the insulation is carried up to meet the loft insulation, and is installed properly or you'll get cold spots and more damp.

If your new windows have vents, that'll help with the condensation.

A cheap option would be to use a foam backed plasterboard, fixed to the existing wall. It should form a warmer surface and hence not be as prone to condensation.

 

[Richard C]

Cavity insulation in situ is not a DIY proposition; it would be impossible to entirely fill the cavity even if the reveal is open behind the frame, which it shouldn’t be; better to get the new windows fitted & then get it injected by an approved installer. Cavity wall insulation is also “controlled building work” which must be notified to your LABC unless you use an approved installer; get it wrong & it could give you all sorts of problems.

A DIY proposition would be to insulate on the inside with specialist insulation boards, especially if turns put to be a single skin wall.

 

[cmother1]

Greetings to someone else from Surrey. You don't say how old your house is but if your bays are anything like mine you'll have 2" cinder block upstairs, rendered on both sides and a 9" solid brick bay on the ground. My place is 30s. Check outside (if you can see your bricks) and see if there are headers showing under the bay window (ie the ends of bricks rather than the sides). If so your walls are solid. The only way to insulate these is on the back - polyurethane foam and plasterboard preferably.
Must get round to doing it myself, someday.....

 

[WhiteChristmas]

Told you my mind was small and simple.

I didn't think about the work being notifiable.

It's a 30's house which has been rendered so I am unable to see the brickwork. I think I might go for the foam backed wallpaper option as the current wallpaper needs replacing anyway.

cmother1, if you fancy coming round and doing mine before you do yours, you are more than welcome

Cheers for your help everyone.

Chris