Yet another insulation question
I’m building in New Hampshire and have three opinions plus my own about how to insulate my cathedral ceiling.
First insulation guy–all closed cell foam for a “hot” roof.
Second insulation guy–1-2″ closed cell foam and fill the bay with open cell, still a “hot” roof.
Third insulation guy–all open cell. Says closed cell is a waste of money.
Carpenter, and my own inclination, soffit vents and a ridge vent with Accuvent running from the soffits to the ridge and some sort of foam sprayed over the Accuvent.
When the first insulator suggested a “hot” roof, which I had never heard of before, I called the shingle manufacturer (GAF) and was told that there would be a warranty issue if there were problems with the shingles and the roof was unvented. I wouldn’t expect problems but the excavator who did my dirt work told me that he was talked into a “hot” roof and five years later had to reroof. Incidentally, he was right about most everything else he suggested from who to get to drill the well to how to situate the septic tank, so I give what he said about his roof a lot of credence, even though he usually deals with the bottom of projects rather than the top.
So, given that I am going to vent the roof using Accuvent (unless someone can give me a compelling reason not to) what foam should I use over it: closed cell, mixed or open cell?
Finally, has anyone had experience with “Accuvent”. The last time vent strip I used was made out of the same stuff they pack a dozen eggs in and I was not at all impressed by it. It probably would disintegrate if sprayed with foam. I really don’t want to (and am not going to) create vent channels with furring strips and plywood or masonite or whatever, which might be the best way to go but is a little too labor intensive for my taste. (Same reason I’m not going to use Roxul in the ceiling but will in the walls.)
Thanks very much.
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