Does anyone have any advice or suggestions concerning this wall?

R-60 wall sketchup drawing

The exterior will be covered with Tyvec then Canexel siding on 3/4" strapping. Canadian building codes require the vapor barrier as indicated.

Thanks.

Explain the reasoning behind the 2" of foam outside the rim and the 2" of foam outside of the sheathing. With a double wall cavity filled with cellulose, you already have a superinsulated wall with nearly no thermal bridging.

Hi DickRussell:

The 2" outside the rim is to help eliminate air leakage at both the rim joist and floor - overkill?

The 2" outside the sheathing is to add R-10 & help air-seal the house, and, it seems that it is recommended to place insulation over the sheathing - am I wrong?

Thanks for your input.

Robert,
How do you propose to build it? The outer (1x2) stud is not sitting on anything so it must be hanging from the roof or somehow tied into the inner studs. Why are there 2 sets of inner studs? Where is the shear bracing? 1x2 framing under plywood will NOT qualify as adequete bracing! The exterior foam, adds cost and reduces the ability to dry to the outside so it would be more cost effective, and actually a 'better" wall if the cellulose were thicker (say 3") with no exterior foam. The 2" foam around the rim joist is not economically justified as it raises the r value in the area where it is by only r2.6 (using your value for the cellulose) over the case where more cellulose was used. BTW you assumed r 3.7/inch for cellulose which is high for even dense pack It would however be a good idea to use spray foam on the interior of the rim joist to improve air sealing there. If you insulated the interior "service cavity" you could pick up r 10 for the wall above the sub floor, quite economically. Do you have contractors experienced in dense packing deep cavities?

Foam (of any kind) is not needed for great air sealing. It might be best to copy some of the double wall designs that are in use.