th attic has some fibergless batting and some blown. we have a split geo thermal heating system part of which is located in the attic. This replaced an oil furnace located in the attic. the attic gets very hot in the summer. I know it needs more insulation and air leaks sealed. my question is, can i put spray foam insulation in the roof area when there is insulation on the floor? will it make a difference? someone mentioned i would need to put a vapor barrier in the floor area. if so under or on top of the insulation?
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It usually makes more sense to insulate and seal the living space and fully ventilate the attic with continuous soffit and ridge venting.
adding attic insulation
the attic has ridge venting, not sure if soffit is continous, could be blocked when last person blew the other, hopefully if blocked the insulaters I hire will do a proper job and fix what is needed.My intent is to seal the living space and add more insulation. my concern is with the geo and duct work in the hot attic I wondered if adding spray foam in between the roof rafters would help or would a problem be caused. The duct work and the unit is wraped in insulation. The roof is new and is black asphalt shingles.
You will create what is known as a "hot" roof if you spray foam in the rafters. You will find arguments on either side of this technique. In my view, you create a closed roof frame with a "hot" roof. If there are leakage issues that go undetected, all the nasty stuff can happen and quickly degrade areas deep into the structure. There is thought that it makes a hotter roof surface leading to early shingle failure. Since it's unvented, moisture will have a hard time dissipating. That moisture can come from simple condensation. It's one thing to have an ideal installation at the beginning but keeping everything tight over the long term is a different matter. I wouldn't want to risk future problems that might effect sheathing and framing.
hot roof
I agree with hammertime-not an idea I like although they are doing it around here.
I would not want to risk the possible damage down the road.