Hi all,

I am renovating a freestanding 2-car garage at my house into a full time woodshop. The location is in Southern Maine and the building will have a heat pump for heating and cooling to keep it hospitable in the winter and keep the humidity down in the late summer.

I am looking for advice on how to insulate the roof.

The shop has a hip roof and the ceiling is relatively low.

As a result, I would like the insulation and sheetrock layer to be on the underside of the roof so I can leave the ceiling open as it is now for higher headroom between the framing.

Some photos of the ceiling/roof framing below. There is original board sheathing and relatively new (2 years old) asphalt shingles on the roof.

My goal is sound attenuation more than R-value. I plan to insulate the walls with Roxul and then down the road when I re-side the building, potentially add an exterior layer of Roxul as well.

My question is how to approach the roof. Am I okay if I spray foam on the underside of the roof sheathing, making it an unvented assembly, and then install drywall under the roof? Or will this lead the moisture problems?

Thanks all for the help