I sketched up a similar system for a friends TF here in VT. Double wall, 2' OC. staggered, with the window / door framing passing through the whole depth. 2x4 with 2x10 top and bottom plates.

He ended up getting a great deal on SIPs, so he wrapped the house with foam and OSB and has been happy ever since.


Insulation - I'd consult with an expert and try to use wet cellulose. I like the idea leaving the inside open... makes lots of things easier. Just space the framing off the frame with a suitable dimension - for drywall 5/8" works, for plaster / etc. 3/4" or more, depending on the substrate.

That extra layer of OSB or plywood will likely make this pretty expensive. Have to think on that bit. You are essentially building 2 walls now.

I never understood hanging the drywall on the frame. It gets wet, damaged, etc.