The exterior walls of the net zero ready house will be made from a double stud wall filled with blown in insulation. The double stud wall is basically two traditionally framed walls placed a few inches apart which create a space in between for an extra thick layer of insulation. The exterior wall of the double stud wall will be the load bearing wall and will be made from 2 x 6 studs spaced at 24 inches apart. The interior, non-load bearing wall will be constructed of 2 x 4 studs also spaced at 24 inches apart.
A vapour barrier and drywall are attached to the interior wall. House wrap and siding are attached to the exterior wall. In between the interior and exterior surfaces will be 12.5 inches of insulation, likely dense packed cellulose with an R value of 3.8 R/inch, giving the walls an R-value about 47.5.
The double stud wall seems to be the most cost effective way of achieving the desired high R value. Using other methods and materials, such as ICFs or SIPS, may have resulted in somewhat thinner walls but would have been much more expensive.
The frame for the house will likely be prefabricated in sections by a factory framing shop, then transported by truck and assembled at the build site. The Europeans have got this down to a super efficient, highly customizable, assembly line. Here's a video:
I'm not sure how it's done here in Toronto but we'll find out soon enough.
