Insulated Garage- stepped foundation wall – stretch code
Hi-
I am working on a garage in a stretch-code town that has a stepped foundation wall on the sides and back of the garage as the grade slopes up about 3+ feet above the slab. To reach R-30 where there is concrete I was planning to use the Zip Sheathing with insulation as well as a 2×4 wall on the interior filled with insulation. On the second floor (an accessory apartment), I am hoping to maximize space fill 2×6 walls with closed-cell foam, and switch to the Zip sheathing without insulation. Is it okay to switch between the Zip insulated sheathing and the regular Zip sheathing? (FYI- the framing above the concrete will also be a 2×6 wall) Is there a better way with more continuity without sacrificing square footage?
Thanks for your thoughts.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
In most cases it should be fine to mix Zip with Zip-R. In other cases, structural engineers prefer to keep the framing plane continuous. But if you're not in a seismically active zone or a very high-wind zone, you should be fine.
Insulating between studs with closed cell foam is generally a waste of resources, though. https://www.greenbuildingadvisor.com/article/installing-closed-cell-spray-foam-between-studs-is-a-waste. For performance, health and environmental reasons, I would continue the Zip-R over the entire wall and use a benign insulation such as cellulose or wood fiber in the wall cavities.
Thank you!