Hi everybody!
This is my first ever DIYnot post after many many months of very useful sifting - thanks everybody!
I am doing a dormer conversion. We are really pushing to get maximum head height. For this reason i would prefer to have insulation between the joists as with a cold flat roof construction.
BUT - as we are pushing head height, our dormer meets the roof ridge right at ridge level, so any vents - and Building Regs seem to require a lot of them - will be a little too exposed in my opinion. I have read a bit about them leaking, which I would like to avoid!
So - a solution I would like to propose is: Making a WARM FLAT ROOF construction, but instead of putting the insulation above the structure/joists as seems to be normal, I propose to include the joists effectively as insulation (I believe wood is -quite- good for that) and install a proper vapour control layer underneath the joists.
It seems to me that the essence of a Warm Roof Construction is that there is insulation above anywhere where condensation could collect - while a cold roof lets condensation collect and escape above the insulation. So why not just move the joists (am I repeating myself?) to WITHIN the insulation layer, and the moisture control to below the joists, rather than just above it?
I can't find anything about this anywhere else online and I'm not sure why.
I look forward to hearing what you have to say...
Jon
This is my first ever DIYnot post after many many months of very useful sifting - thanks everybody!
I am doing a dormer conversion. We are really pushing to get maximum head height. For this reason i would prefer to have insulation between the joists as with a cold flat roof construction.
BUT - as we are pushing head height, our dormer meets the roof ridge right at ridge level, so any vents - and Building Regs seem to require a lot of them - will be a little too exposed in my opinion. I have read a bit about them leaking, which I would like to avoid!
So - a solution I would like to propose is: Making a WARM FLAT ROOF construction, but instead of putting the insulation above the structure/joists as seems to be normal, I propose to include the joists effectively as insulation (I believe wood is -quite- good for that) and install a proper vapour control layer underneath the joists.
It seems to me that the essence of a Warm Roof Construction is that there is insulation above anywhere where condensation could collect - while a cold roof lets condensation collect and escape above the insulation. So why not just move the joists (am I repeating myself?) to WITHIN the insulation layer, and the moisture control to below the joists, rather than just above it?
I can't find anything about this anywhere else online and I'm not sure why.
I look forward to hearing what you have to say...
Jon