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17,000 dryer fires a year, when did you last clean the inside of the dryer near motor or the exhaust ducting?
I understand that cc spray foam is getting more popular against roof sheathing, but I always worry about a tiny little leak somewhere. If the foam is several inches thick, I don't see your sheathing drying, but I do see it rotting. Maybe the roofing material is moisture permeable enough (depends on what you use), but I'd at least make sure my sheathing could breathe to the outside if I foamed it inside. If you do not spray the roof, then I'd suggest you look at blowing in cellulose instead of fiberglass.