In mid February the founders of ByggHouse gathered in Rockford, Ill for a team meeting, and for a team building activity we undertook the construction of a mock-up of a nordic layered wall using American building materials and components.
the interior side layers
I've been describing this wall assembly in the talks I've given over the past few years, and I have multiple diagrams and several videos explaining the configuration of USA New Wall and Swedish Platform Framing. But at times having a physical mock-up speaks louder than words or drawings, so we set out to build the mockup you now see here.
the outside layers
For the exterior layers we limited the continuous insulation to 1.25" to keep the bulk of the mock-up down. However this 1.25" of stone wool corresponds to R5 insulation value, which is the value for exterior insulation which is frequently called for in the IRC building code in order to meet the requirements of the most current energy codes. Given that, higher total insulation value can be attained with 2", 3", or 4" of continuous exterior stone wool.
Similarly we used at 2x6 stud wall assembly for the mock-up again to reduce the bulk. Into the stud cavities we fitted R23 Roxul stone wool. When higher insulation values are desired a 2x8 assembly would be used, which would accommodate R30 stone wool batts. Since the dimensions of our mock-up were reduced from actual construction we had to trim all of the insulation pieces to fit the odd sized cavity widths. And of course we did that with the SkarBord cutting table.
cutting with the SkarBord gives a perfect fit
On the inside we can see the service cavity where all the wiring can run inboard of the vapor control and air sealing sheet. In this case we've used a sample of the Intello+ variable permeability membrane for the air sealing and vapor control sheet. Since all the electrical work is inboard of this sheet there is no need to make a hole in it for each light switch and receptacle which makes it much easier to make the house air-tight. Speaking of electrical work, one of the most frequent questions is how to install electrical boxes into this 1.5" service cavity. Simple, as you see here, a 4x4 box with a switch plate reducer cover handles typical devices, and is also available in double gang configurations. These boxes are a few cubic inches larger than typical single gang boxes, and actually give you a little bit more room to work. Up above you can see the ledger board which lives in the depth of the same service cavity, and once placed such allows us to keep the bearing end of our floor joists inside of the air tight sheet, and allows the main stud cavity insulation to extend all the way to the top of the joists.