Adding Insulation to a crosswall house

12 Posts

I have recently bought a 1970s crosswall house.
All my external walls are studwall. There is no brick outerskin.
I believe there is some ancient rockwool between my studs, and then plasterboard over that internally. I can't quite tell from the gap I've been peering into where any VCL is fitted at the moment.
I am thinking about pulling off the plasterboard. Removing the old rockwool. And putting celotex between the studs. The wall isn't very thick so I don't think I will actually get much celotex in there - but it has to be better than some ancient rockwool! My walls in total are ~200mm thick from inside face of the plasterboard, to the external render. I am hopeful that I could get 50mm celotex in.
So questions:
1) I believe I need a VCL on the warm side of that - how do you seal that against the ceiling / floor / party wall / other internal walls? I am going to end up doing this one room at a time so I think I am always going to have some gaps at the ceiling / floor, and the internal walls. Is that a problem? Especially if I go through next winter with some of the rooms done, and others not?
2) I know ideally you would have another layer inside to stop the studs being a thermal bridge. But that would result in losing floor space, and having to move electrics and plumbing which turns this into a much bigger job which I'd like to avoid. Is it actually going to cause me problems? Or is it just less benefit than I could have? I've read about shadowing etc, but I am unclear how much this should concern me.
3) In terms of a VCL - Is there any chance my existing VCL is on the OUTSIDE of the rockwool? And if so is there any problem putting more insulation inside that provided I have another VCL inside.
4) My plan would be to use foil backed celotex - however I would probably still apply a continous VCL sheet inside that fixed to the studs. Do I still need to tape up the joints in the celotex in that case?
All my external walls are studwall. There is no brick outerskin.
I believe there is some ancient rockwool between my studs, and then plasterboard over that internally. I can't quite tell from the gap I've been peering into where any VCL is fitted at the moment.
I am thinking about pulling off the plasterboard. Removing the old rockwool. And putting celotex between the studs. The wall isn't very thick so I don't think I will actually get much celotex in there - but it has to be better than some ancient rockwool! My walls in total are ~200mm thick from inside face of the plasterboard, to the external render. I am hopeful that I could get 50mm celotex in.
So questions:
1) I believe I need a VCL on the warm side of that - how do you seal that against the ceiling / floor / party wall / other internal walls? I am going to end up doing this one room at a time so I think I am always going to have some gaps at the ceiling / floor, and the internal walls. Is that a problem? Especially if I go through next winter with some of the rooms done, and others not?
2) I know ideally you would have another layer inside to stop the studs being a thermal bridge. But that would result in losing floor space, and having to move electrics and plumbing which turns this into a much bigger job which I'd like to avoid. Is it actually going to cause me problems? Or is it just less benefit than I could have? I've read about shadowing etc, but I am unclear how much this should concern me.
3) In terms of a VCL - Is there any chance my existing VCL is on the OUTSIDE of the rockwool? And if so is there any problem putting more insulation inside that provided I have another VCL inside.
4) My plan would be to use foil backed celotex - however I would probably still apply a continous VCL sheet inside that fixed to the studs. Do I still need to tape up the joints in the celotex in that case?
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Treasure the moments that you have. Savour them for as long as you can for they will never come back again.
Is the celotex you are going to use have a fire retardant added.
If I do this though I'd like to think I am starting off by approaching building control with a good plan!
2021 mortgage and debt free, working part time and living the dream
Treasure the moments that you have. Savour them for as long as you can for they will never come back again.
Insualted plaster board will eat into the room.
Plus I've never really understood with insulated plasterboard how that works given it must go on the warm side of any VCL.
Insulation that is only as good as rockwool, but more expensive. Add in the cost of pulling off and replacing the plasterboard I just can't see it stacking up
Treasure the moments that you have. Savour them for as long as you can for they will never come back again.