attic insulation question
IMO, the 3" spray-foam, plus the fibreglass, would have been enough (in terms of insulation, air barrier and vapour barrier) had the attic not housed the furnace. And I think that's the kicker; fire regulation perhaps dictate that it be covered with drywall, I don't know, but precaution may be the reason behind it...And even if the furnace weren't up there, some codes might say to cover it anyway. But it's moot and I'm assuming the HERS rater know his local building code.
But from an energy loss perspective, yes, I'd cover it. Just how you get drywall up there doesn't change that opinion just makes it a challenge.
No need for a vapour barrier with that foam and no real need to insulate the attic floor. Air-seal would be better time spent. And you don't want it too tight, the furnace has to breathe.
I wouldn't bet on any shingle warranties helping you out; in any claim, the most Certainteed would do for you with that set-up is refund you the cost of the shingles if you can prove they were faulty. You'll get in the neighbourhood of 15 years, that's it.
PS: Oh yeah: you say you are building a new house? I thought new codes insist on roof venting (i.e a gap between the roof and the insulation).
Last edited by ccarlisle; 03-01-2010 at 09:47 AM.