Is this a good insulation strategy for apartment over garage (new construction)?
In early planning stages for a detached single-car garage/small shop with ~600 SF apartment above, as accessory dwelling unit (rental) to my house. Would like to approach Passive House standards for air sealing and overall energy use.
Footprint ~ 14′ x 42′, on a relatively narrow, deep lot. Thickened slab foundation. Stair to second story apartment inside building envelope. Climate zone 5, 6700 heating degree days, 10F winter design temperature.
Considering Remote wall system, as follows (from inside out):
First floor wall : Drywall, 2×6 stud wall w/ R-19 batts in cavity, OSB sheathing, water/air barrier (Grace Ice & Water or 6 mil poly), 4″ EPS foam, horizontal 3/16″ coroplast furring, corrugated metal siding.
Second floor wall: same as above, except 2×4 studs, R-13 batt, and 6″ EPS.
Garage ceiling: drywall, 2″ EPS, 11 7/8″ TJIs w/ blown cellulose, subfloor. Not sure about air sealing.
Roof: Cathedral 12/12 pitch (pitch matches existing house). Leaning toward open-web floor trusses used as rafters, with blown cellulose. Foam over sheathing (2″ ?), corrugated metal roofing. Not sure if this assembly is best vented or unvented. For aesthetics, considering a plywood ceiling in apartment–will this be adequate for air sealing?
Thanks in advance for input.