- Reaction score
- 479
Strictly speaking you have to worry about airtightness and limiting u values as well as the overall u value, which will be fine.
The limiting u value is about 0.8 for ceilings and is there to prevent black mould on cold spots or interstitial condensation, hence why you always get some insulation below or above the joists. But even 25mm of celotex would be fine for that, or a velux window would be OK.
The airtightness is just avoiding the heat bypassing the insulation, otherwise it's a bit like walking around wearing a down jacket but forgetting to zip it up. Or leaving an open velux window. That's the important one for heat loss and loft condensation.
Hope that makes sense! But the building inspector isn't trying to be difficult.
The limiting u value is about 0.8 for ceilings and is there to prevent black mould on cold spots or interstitial condensation, hence why you always get some insulation below or above the joists. But even 25mm of celotex would be fine for that, or a velux window would be OK.
The airtightness is just avoiding the heat bypassing the insulation, otherwise it's a bit like walking around wearing a down jacket but forgetting to zip it up. Or leaving an open velux window. That's the important one for heat loss and loft condensation.
Hope that makes sense! But the building inspector isn't trying to be difficult.
