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I live in a 1970s "chalet-style" ex-council house, so all of the 2nd floor is in the roof, and I want to add some insulation. I think there's 3 separate parts:
1. The vertical gable walls: cavity blockwork, currently 50mm studs affixed to the inside with 20mm bits of polystyrene between some of them and plasterboard over the top. I plan to replace the polystyrene with 50mm celotex.
2. The walls meeting the roof: Currently there's some soft insulation in the eaves which I plan to top up. Then on the knee wall and sloping roof I want to add 50mm celotex, again between existing wooden studs. That will leave 70mm between the insulation and the roof for airflow, is that enough?
3. There's about 100mm soft insulation in the roof which I plan to double.
Does that sound ok? Any thoughts appreciated, the house is currently freezing but not damp so I'm trying to be cautious about condensation.
1. The vertical gable walls: cavity blockwork, currently 50mm studs affixed to the inside with 20mm bits of polystyrene between some of them and plasterboard over the top. I plan to replace the polystyrene with 50mm celotex.
- Are the wooden studs going to be a cold bridge? Should I be insulating over the top of them too?
- I think I need a vapor barrier on the warm side of the celotex - does that go over the top of everything including the wooden studs?
- There's a 10-15mm gap between the wooden studs and the block wall - will it be a problem to have that gap behind the insulation?
2. The walls meeting the roof: Currently there's some soft insulation in the eaves which I plan to top up. Then on the knee wall and sloping roof I want to add 50mm celotex, again between existing wooden studs. That will leave 70mm between the insulation and the roof for airflow, is that enough?
3. There's about 100mm soft insulation in the roof which I plan to double.
Does that sound ok? Any thoughts appreciated, the house is currently freezing but not damp so I'm trying to be cautious about condensation.