You guys might find this build from Alaska quite interesting.
A Passivhaus Design for Alaska
The SunRise Home. | GreenBuildingAdvisor.com
It's a play off the REMOTE/PERSIST method of outboard insulation with foam. This case he built the internal walls as the structural walls, with the exterior sheathing acting as the air barrier, and wrapped the ceiling 2x4 service channel with sheathing as well to complete the airtight box. He then rolled the trusses onto the walkable ceiling plane, and built exterior truss type walls wrapped in WRB which were then filled with cellulose.
There's tons of comments/build specs in the comments... Definately worth a read for anyone interested in passive house / superinsulation, and new building techniques in general.