How to insulate an enclosed garage ceiling?
In my work as a building analyst here in Southeast PA, I meet lots of homeowners having comfort issues in conditioned spaces above garages. Typically these spaces are cold in the winter, though not necessarily warm in the summer. Quite often, there is fiberglass batt in the ceiling cavity of the garage (covered by drywall). In many cases, the batt has kraft paper and is facing down towards the unconditioned garage, sometimes up against the floor and sometimes lying on top of the ceiling. I’ve shied away from recommending a dense pack approach in these situations, concerned that the assembly would have less chance of drying out if it were to ever get wet. Between plywood, carpet/flooring padding, carpet, etc. above and the kraft paper below I get a little nervous!
However, in reading this article on GBA, my thinking is shifting a bit… https://www.greenbuildingadvisor.com/blogs/dept/building-science/should-paper-facing-batt-insulation-face-inside-or-outside
Since the kraft paper is a vapor retarder and not a vapor barrier, should I really be so cautious, even if it is technically installed incorrectly? Are there even that many ways for moisture to get into the ceiling cavity? Outside of the garage wall assembly/rim/band joist I can’t think of many, other than a pipe breaking or some sort of flood from above. Nor can I see much diffusion from the interior of the house making its way downward into the floor/garage ceiling assembly…
So with all that said, is there a hard and fast approach to all/most garage ceilings or should I keep being paranoid in PA? (Any recommendations on techniques, materials, etc. would be greatly appreciated!)
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