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Here is some more detail for those who read this under “attic ventilation”
I insulated the vaulted ceilings, kneewalls, and endwalls of our small cape with kraft faced R-13 FG and a 4-mil poly VB. I was limited to R-13 because of the 2×6 rafters. The poly barrier is continuous over entire attic ceiling from sill to ridge, with no light fixtures. I have a shingle-over ridge vent and soffit vents at the frieze and I installed polystyrene raft-r-mates to create a continuous air space from soffit to ridge.
Recently I poked around and discovered an alarming amount of condensation on the FG bats and the FG side of the raft-r-mates. I didn’t want to expose the FG to the outside air but it seams like the raft-r-mates are blocking moisture from reaching the air space. Shouldn’t any moisture trapped during humid summer renovation in the insulation cavity should easily exit through via the rafter mates and ridge vent?
There is also moisture behind the FG bats in the sidewall. It’s my understanding that the moisture in the wall cavities will follow the vapour pressure gradient and migrate through the sheathing to the outside air which is dry and cold at present. Note: sheating is covered with 30# felt and painted wood siding. Is this too much for moisture to get through?
I’m sure the source of moisture is from the interior (cooking, bath, and occasional vaporizer use). The attic space is above the kitchen–kitchen ceiling and walls have cellulose with no VB.
Was I wrong to install a poly barrier? or did I just screw it up? Should I pull off the poly barrier and let the moisture dissapate into the attic? What about the rest of the attic/ house that has already been drywalled?
Replies
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Here is some more detail for those who read this under "attic ventilation"
I insulated the vaulted ceilings, kneewalls, and endwalls of our small cape with kraft faced R-13 FG and a 4-mil poly VB. I was limited to R-13 because of the 2x6 rafters. The poly barrier is continuous over entire attic ceiling from sill to ridge, with no light fixtures. I have a shingle-over ridge vent and soffit vents at the frieze and I installed polystyrene raft-r-mates to create a continuous air space from soffit to ridge.
Recently I poked around and discovered an alarming amount of condensation on the FG bats and the FG side of the raft-r-mates. I didn't want to expose the FG to the outside air but it seams like the raft-r-mates are blocking moisture from reaching the air space. Shouldn't any moisture trapped during humid summer renovation in the insulation cavity should easily exit through via the rafter mates and ridge vent?
There is also moisture behind the FG bats in the sidewall. It's my understanding that the moisture in the wall cavities will follow the vapour pressure gradient and migrate through the sheathing to the outside air which is dry and cold at present. Note: sheating is covered with 30# felt and painted wood siding. Is this too much for moisture to get through?
I'm sure the source of moisture is from the interior (cooking, bath, and occasional vaporizer use). The attic space is above the kitchen--kitchen ceiling and walls have cellulose with no VB.
Was I wrong to install a poly barrier? or did I just screw it up? Should I pull off the poly barrier and let the moisture dissapate into the attic? What about the rest of the attic/ house that has already been drywalled?