Looking through the search function, I can see this has been discussed lots but I have some specific questions.
I live in a house in Scotland with 600mm Sandstone walls, externally rendered. I'm renovating one of my rooms and want to insulate the external wall (internally). Internally there is no insulation but the wall surface is 80mm from the stonework. My plan was to build a stud wall, 25mm away from the stonework, 40-50mm of Celotex/Kingspan sheet inside the stud-work sealed with expanding foam or foil tape as required to ensure a vapour barrier. Then 12.5 mm plasterboard and skim.
1. In an effort to prevent damp, I think it would be a good idea to ensure the 25mm void is vented to the outside air. We currently have an air-brick on that wall, albeit adjacent to a different room. I was thinking of trying to connect the wall void to the void space under the floor, maybe via a series of holes. Is this likely to be enough to prevent damp, assuming the vapour barrier is complete?
2. Would I lose any meaningful insulation properties where the studs are instead of the insulation board (i.e every 600mm)? Obviously my other choice would be Kingspan K18 board onto battens where the insulation coverage would be complete.
3. Inside the window reveals, I don't have quite as much space so was thinking of using 12mm Celotex and plasterboard. Would I still need a 25mm void space or would I be able to get away with less?
4. I was initially looking at the Kingspan K18 board onto battens but my concerns there are: How do you maintain the vapour barrier when you join two boards together? Is there some sort of sealant you can put between them as you install them? Also it looks to be a lot more expensive but I can live with that if there are noticeable benefits. Is there a preferred method between my two suggestions?
Sorry for the long post, all my research started to get contradictory so I thought I would ask.
Thanks, Chris.
I live in a house in Scotland with 600mm Sandstone walls, externally rendered. I'm renovating one of my rooms and want to insulate the external wall (internally). Internally there is no insulation but the wall surface is 80mm from the stonework. My plan was to build a stud wall, 25mm away from the stonework, 40-50mm of Celotex/Kingspan sheet inside the stud-work sealed with expanding foam or foil tape as required to ensure a vapour barrier. Then 12.5 mm plasterboard and skim.
1. In an effort to prevent damp, I think it would be a good idea to ensure the 25mm void is vented to the outside air. We currently have an air-brick on that wall, albeit adjacent to a different room. I was thinking of trying to connect the wall void to the void space under the floor, maybe via a series of holes. Is this likely to be enough to prevent damp, assuming the vapour barrier is complete?
2. Would I lose any meaningful insulation properties where the studs are instead of the insulation board (i.e every 600mm)? Obviously my other choice would be Kingspan K18 board onto battens where the insulation coverage would be complete.
3. Inside the window reveals, I don't have quite as much space so was thinking of using 12mm Celotex and plasterboard. Would I still need a 25mm void space or would I be able to get away with less?
4. I was initially looking at the Kingspan K18 board onto battens but my concerns there are: How do you maintain the vapour barrier when you join two boards together? Is there some sort of sealant you can put between them as you install them? Also it looks to be a lot more expensive but I can live with that if there are noticeable benefits. Is there a preferred method between my two suggestions?
Sorry for the long post, all my research started to get contradictory so I thought I would ask.
Thanks, Chris.
