Spray foam, blown in and trusses..
I have a new construction house with trusses and an unvented roof assembly. Was originally going to use only spray foam on underside of roof decking to get my r value (and a “hot roof”), but, due to LARGE cost overruns on other aspects of the project, looking for ways to cut down costs.
Since roof assembly is trusses (so only 3.5 depth – no easy way to do flash and batt etc.), unvented and hvac equipment is in attic (duct work is insulated), I am somewhat limited on my budget oriented choices now.
But I did have a thought:
What about 3 inches of spray foam on underside of roof decking (to meet 40 vapor impermeable code requirement for hot roof) and remainder of required r value using blown in on attic floor?
Walls will be fiberglass Batts.. I did air sealing using zip tape on sheathing already.
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