I’ve decided to start this project by lining the walls with Owens Corning Foamular 250. It comes in 8′ x 2′ sheets and costs about $20 at Home Depot. It has an R-10 rating, which might be sufficient on its own, but I think I’ll add unfaced insulation to bump it up even higher. I’m staying away from faced insulation on the perimeter walls because I don’t want to invite mold to the party. I’ve attached it to the walls using Loctite PL300 foam board adhesive. The joints are sealed with sheathing tape I found on Amazon.
Next up… starting my first wall!