In case anyone is wondering… our house will have 4″ of rigid insulation on the exterior of the framing and sheathing, topped by vertical furring strips and gigantic screws thru those 4+ inches and into the studs to hold everything up. And then the siding attached to that. Just as described here as a “good idea”: LINK
We are also doing a double-stud wall on the interior, with 2″ of closed cell foam and 9.5″ of cellulose. “Flash and fill”. This means we don’t have to do the dew-point calculation to see what the temp of our sheathing is to prevent winter-time condensation (balancing inside and outside insulation) per calc in Joe Lstiburek’s Builder’s Guide to Cold Climates.
That’s an R-value approaching 70 I reckon, a bit lower with thermal bridging, though with 4″ of rigid, we’re in good shape. Vs R-13 for a typical 2×6 wall filled with fiberglass batts, cellulose, icynene, etc. (R-19 but R-13 after accounting for the thermal bridging every 16″ or 24″ and at the joists.)