Dense-packed cellulose in attic rafters with Ice and Water Shield on exterior
After having an energy audit perform, it was recommended that I have the attic rafters dense packed with cellulose opposed to insulating/air sealing floor in order to bring the HVAC equipment up there into the conditioned space. Also, 3 cathedral ceilings going into the attic made doing the floor too challenging.
The home is located in upstate NY and the attic is currently vented with kraft faced fiberglass batts on floor. The problem is that the entire roof is covered in ice and water shield which is obviously vapor impermeable (asphalt shingles on top of that). The contractor recommended converting the vented attic into an unvented attic and maintaining the openings at the ridge and soffit (no baffles on the underside of roof deck).
The contractor told me that when cellulose is dense packed to the proper density, air and water vapor shouldn’t be able to easily get through it from the interior. In the event any moisture does get into the cellulose, it will disperse throughout the material and find its way to the openings at the soffit or ridge rather than trying to diffuse through the wood which obviously has a vapor impermeable membrane on the other side. He said that the 2×10 rafters would be insulated to roughly R35 (effective r value less due to thermal bridging) and that the roof deck should be kept warm enough to prevent water vapor from condensing on the sheathing.
I just wanted to get some of your opinions on this route. Am I asking for trouble by eliminating venting and only allowing drying to the interior? I’d really like to make the attic conditioned but obviously don’t want to cause any rotting potential.
Am I better off just accepting the air leaks on attic floor and furnace in attic? If I chose not to insulate rafters, I would upgrade flex ducts from R4.2 to R8 and install a 2 stage furnace which would increase efficiency but it obviously can’t be a condensing furnace in an unconditioned space.
I’m sure some of you will recommend using spray foam instead but we are not interested due to potential health concerns. Thanks for your thoughts in advance!