Roof insulation for office shed
I’m in zone 5 and am building a 10×12 office shed anchored to a 12x14x4″ insulated concrete slab. The unit will have a small mini-split for heating/cooling. There will be zip sheathing on the walls and the outer layer of the roof. I’m having difficulty deciding how to insulate the roof. I’m thinking a hybrid solution of foam insulation above the sheathing and rockwool below the sheathing. There’s also R-15 comfortbatts between the studs (16″ oc) and R-6 comfortboard covering the exterior wall sheathing.
It has a 2.5:12 pitched roof. It’s a 14x14ft roof with 1′ overhang on each side except front. 2′ overhang on the front.
My plan is for an unvented roof (air tight, no recessed lights) with the following layers:
- Metal Roof
- 7/16″ zip sheathing
- 1-1/2″ EPS foam (staggered & taped seams)
- 2″ high-density EPS foam (taped seams)
- 1/2″ OSB
- 2×6 rafters spaced 16″ oc
- 2-layer R-15 Comfortbatt (tight to ceiling) – No vapor barrier
Is this sufficient to keep the roof sheathing at the proper temp and dry or should I add more/thicker foam boards?
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