Seeking Feedback on this Shed Roof Plan
In Zone 6, northern New England, I have a 104 (8ft x 13 ft) sq ft pier/beam addition on my house (approx 11 years old addition, I’m the second owner to it). Oddly enough, heating wasn’t tied in, yet there was R30 fiberglass in the ceilings, R19 in the walls and some R of fiberglass under the floors. Drywall had encapsulated all of this, which I’ve removed. There are also continuous soffit vents on the long exterior wall, and baffles that run inside of each rafter (2×10’s) bay. The baffles start at the top plate, after the soffit vents and run until about 5″ from the shared wall with the house. Not sure why these didn’t extend all the way. There is no other venting. There is also romex that runs in this ceiling about 4″ down from the roof. I’m new to this, but do not understand this set up. Longstory short, we need to make this a conditioned, finished room (if we can) due to a new kiddo on the way.
My thought is that I can remove the baffles, have a contractor do 3.5″ of spray foam directly to the underside of the sheathing, getting me an R value of 24.5. Then, I can put R-30 rockwool (edit: I mean R-23). This would actually allow me to exceed code (edit: nearly meet code). I assume I wouldn’t then use a vapor barrier/retarder after the rockwool. I would prefer to put on T&G ceiling, but am thinking about re-doing the drywall. Do I spray foam under the sheathing over the soffits? Should I then fill up the rest of that cavity with the rockwool or ask the spray contractors to fill that cavity up? Can/should I leave the soffits vented? Does it matter? If I should block or remove them, can you recommend an airtight approach? Do I need to ensure the spray foam doesn’t encapsulate the romex, or is it OK if I decide to do more than teh 3.5″ spray foam and instead do the full 7″ or so?
For the walls, I’ll be air sealing with caulk or great stuff, using R-23 rockwool and then applying Certainteed as the air seal/vapor retarder.
I’m mostly concerned right now with the ceiling and would appreciate any ground-truthing or nudges to what I’ve suggested above.
edit: best as I can tell there is no insulation on the exterior of this roof set up.
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