Use open cell over closed cell to fill cavities on underside of roof?
The spring project is to have our third floor walkup insulated so it can be a conditioned space. It is a century home, has original tongue and groove flooring. The roofline and exterior walls are exposed to I can insulate the best way possible.
My question is this. Can I spray 1" of closed cell foam on the roofline and exterior walls to air and vapor seal, than spray open cell foam in the remainder of the wall cavity? The open cell will provide additional insulation, noise reduction and is much cheaper than trying to spray closed cell to fill the cavities.
I do not have soffit vents, but I will have to seal off the roofline where it crosses over the house frame. I do have three roof vents that need sealed (piece of plywood than foam, or just spray foam it?)
Second question....are IC recessed lighting acceptable to have the spray foam right against it.
Re: Use open cell over closed cell to fill cavities on underside of roof?
I don't know if the 2 different foam types are compatible. Someone familiar with them could tell you. Asd to the can lights, generally no- they should not be foamed, and many of them are not even supposed to be covered at all. Look inside the light for the maker and model number and check the manufacturer's website to see what is acceptable with them.
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