FWIW my father in law speaks Arabic and works for Boeing, my wife grew up in places where folks speak Arabic. Her dad would listen to the local mechanics describe what was going on with the plane in Arabic, and then call Boeing HQ and talk to someone in English, and then get off the phone and switch to Arabic, you get the idea. She likes it hot.
With 2x6 construction I have R=21 inside the sheathing with standard 5.5" fiberglass, and then styrofoam outside the sheathing under the siding, 1 or 2 layers of 2". I can never seem to remember if it is one layer of 2" that gives me another R20 or two layers of 2", but there is at least one 2 in there.
Current thinking for us is to stick build exterior walls to 11 feet, then stick build rafters on that without having to buy knee trusses. Then a stick built inside ceiling at 8 feet leaves room for a 32" layer of blown cellulose in the ceiling corner to corner. We are currently looking for not more than 1/3 total R value inside the vapor barrier, and at least 2/3 of total R value outside the vapor barrier. Keeping the vapor barrier near the inside keeps the vapor barrier material above the dew point, ameliorating condensation/ moisture/ mold issues.
We can get away with 11' 2x4 construction because we only average about 10" of precipitation annually. Certainly I see three or four feet of snow every year, but it is really dry powder type snow locally. Fluffy. Who knew Fairbanks, AK is considered a world class destination by cross country skiers? I didn't. If you get more than 10" annual precip this may not work for you...
Anyroad, with 32" cellulose in the ceiling we can insulate the 2x4 structure inside the sheathing after the mechanicals are in, and then put the vapor barrier outside the sheathing. No cutting little pieces to fit between the floor joists in the basement and tube after tube of "black death" in the caulking gun to fasten it down. No stupid "hats" over every jiffy box. Just vapor barrier out from under the footer, up the outside of the sheathing, over the rim band, across the "attic floor" before the cellulose gets blown in, and back down the other side.
Once the vapor barrier is up, 6" of styrofoam on the outside, with furring strips to clamp down the styrofoam and hang the siding from. Those 9" screws aren't cheap, neither is the foam board; but heat ain't cheap up here either, I paid $3.86/ gallon for my last fill of heating oil.
One challenge is the HRV (Heat Recovery Ventilation) system. I only know two people in houses tight enough to require them so far, but neither of those two are ecstatic. What the system is supposed to do is push outgoing air from the bathroom and kitchen through a heat exchanger so incoming fresh air to the living room and bedrooms is already warm. I know two is a pretty small sample size. I dunno if the engineers are underestimating requirements, or the subs are cutting corners while the general is on the phone, or the end users are committing RTFM errors, but these should work.
For retro fits, with the shingles off we are looking at 12" of styrofoam on the roof sheathing with furring strips and really expensive screws, then metal roofing on the furring strips. That kind of foam purchase is priced like beef, higher than farm raised salmon, less than wild caught. I'll need a layer of it one foot thick big enough to cover 1200sqft of floor on a 4:12 roof.
If you are building now, or about to, "CCHRC REMOTE wall system" does hit on google, homepage here:
http://www.cchrc.org/remote-walls
