Insulating a bedroom bay window

Hi, I'm quite new to the forums but have been using MSE for awhile.

We are looking for some advice really; last winter we found our bedroom to be really really cold. We put this down to the bay window in our bedroom as it seems to be the coldest area of the room.

I've been in the loft and found out there was no insulation at all above it, so put two layers of loft insulation in there. Not much had changed so presumed the bay is a single skin "wall" with no insulation. But after taking a plug socket off to see inside we found some insulation in a gap between the plasterboard and a chipboard "wall". The outside of the bay window has leading on it so I presume the chipboard sits behind that.

Now, the advice I'm after is what can I do with it? 
As there is a gap behind the plasterboard with a bit of insulation in it can I just put insulated plasterboard on top of the preexisting pb?

Or do I need to take the old pb off and put new insulated pb on?

Or do I need to build a new interior wall around the bay with a bigger gap and put kingspan in there?

Not really sure what I can and can't do as I don't want to cause more problems after doing something.

Comments

  • This is the what I could see through the hole for the plug socket.


  • FreeBear
    FreeBear Posts: 14,248
    First Anniversary First Post Name Dropper Photogenic
    Forumite
    I'd be inclined to remove all the plasterboard and vill the gap with multiple layers of Kingspan/Celotex. At an absolute minimum, 75mm in total. If there is space, go to 100mm or even 150mm. You'd need a wider window board, and some extra support for any electrical back boxes.
    Her courage will change the world.

    Treasure the moments that you have. Savour them for as long as you can for they will never come back again.
  • Thanks for you help.

    Do I need to keep a gap between the chipboard wall and the Kingspan?
  • FreeBear
    FreeBear Posts: 14,248
    First Anniversary First Post Name Dropper Photogenic
    Forumite
    I'd leave a gap of ~12mm or so depending on the depth of the studs. Not absolutely essential though, so I wouldn't get too hung up about it.
    Her courage will change the world.

    Treasure the moments that you have. Savour them for as long as you can for they will never come back again.
  • stuart45
    stuart45 Posts: 3,821
    First Anniversary Name Dropper First Post
    Forumite
    In timber frame construction the insulation is pushed up tight against the OSB sheathing. There is a VCL on the warm side of the insulation to stop moisture getting through. You can put battens on the studs for a service void before tacking the plasterboard. 
  • FreeBear
    FreeBear Posts: 14,248
    First Anniversary First Post Name Dropper Photogenic
    Forumite
    stuart45 said: There is a VCL on the warm side of the insulation to stop moisture getting through.
    If the joints between sheets of insulation are taped, is a separate VCL really necessary ?
    I'm of the opinion that the foil facing of the Kingspan/Celotex type boards already act as a VCL.

    Her courage will change the world.

    Treasure the moments that you have. Savour them for as long as you can for they will never come back again.
  • stuart45
    stuart45 Posts: 3,821
    First Anniversary Name Dropper First Post
    Forumite
    FreeBear said:
    stuart45 said: There is a VCL on the warm side of the insulation to stop moisture getting through.
    If the joints between sheets of insulation are taped, is a separate VCL really necessary ?
    I'm of the opinion that the foil facing of the Kingspan/Celotex type boards already act as a VCL.

    If Kingspan etc is used and the joints done with the correct tape that is the VCL, so a separate one wouldn't be needed.
  • ThisIsWeird
    ThisIsWeird Posts: 4,458
    First Anniversary First Post Name Dropper
    Forumite
    edited 22 November 2023 at 7:47AM
    Hi James.
    Does this bedroom have a part-vaulted ceiling?

    Anyone know the best way to check surface temps? Eg, using a 'gun'-thermometer, or IR camera attachment?
    It would be useful to know just where the cold spots are. Could be draughts from under the skirting, for example.

  • ThisIsWeird, no vaulted ceilings and we have had the windows upgraded just under a year ago
Meet your Ambassadors

Categories

  • All Categories
  • 341.7K Banking & Borrowing
  • 249.7K Reduce Debt & Boost Income
  • 449.1K Spending & Discounts
  • 233.6K Work, Benefits & Business
  • 606K Mortgages, Homes & Bills
  • 172.4K Life & Family
  • 246.7K Travel & Transport
  • 1.5M Hobbies & Leisure
  • 15.8K Discuss & Feedback
  • 15.1K Coronavirus Support Boards