Hello, my name is Mike and I live in Southeastern Pennsylvania. We have a ranch home and we’re building an addition that includes a 2-car garage with a primary suite above it. The exterior is finished along with all the plumbing, electric and mechanicals. I’m ready to insulate but I’ve been going down the rabbit hole on this topic and feeling overwhelmed by all the information and can’t determine the best approach for my situation.

We have a shed-style roof with a vented vaulted ceiling and 2×12 rafters. I would like to avoid using spray foam and avoid furring out any rafters since the rough electrical is already done. We’re on a budget and I’d like to keep things as simple as I can.

CEILING:
Planning to do a 1.5″ air gap for the soffit vent, then 4″ of foil-faced poly-iso, batts in the remaining 5.5″, then drywall. I plan to secure the rigid foam to the rafters so the surface of the foam will act as the baffle for the air gap above it.

WALLS:
Planning to fill the 2×6 walls with batts.

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We live in a mixed humid climate (we touch triple digits in summer and single digits in winter) and my biggest concern is condensation/moisture becoming trapped in the ceiling/walls. Will my proposed assembly keep things dry? Do I need some kind of additional vapor retarder in the ceiling or walls? Any advice would be greatly appreciated!

Thank you in advance!
– Mike