Anything thoroughly coated with tar or wrapped in Tyvek is airtight and watertight for insulation purposes.
With that caveat, I concur heartily with @HippityHop, especially in re: lack of diagonals in this house kit.
I’ve actually seen plenty of nail-and-glue free buildings; my recently rebuilt stable is pegged mortise and tenon, and there have been some SIP systems made to lock together without nails. But oddball, creative stuff like this is a big reason I keep coming back to bOINGbOING, regardless of how practical it might be!
