Qwertyjjj
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These buildings weren't really designed to have any insulation at all. As such, they require some heat to melt all the snow on the roof in winter otherwise it becomes too heavy.
The experts advise putting some insulation at least due to the dew point in this space. So, they advise R8 or R10.
Now my dilemma is that I cannot easily find fiberglass in r8 locally. In addition, the joists are spaced irregularly, about 27" apart.
Is it possible to buy R20 and just split it in half to become R10?
Secondly, we were advised not to use cellulose on this ceiling since it would sag on the vapor barrier and touch the drywall but I'm wondering if cellulose wouldn't be better just due to the irregular joist spacing?
I could use stryofoam but then does it go at the top or bottom of joist bay? Bay is about 8" deep