Its kind of tough to define the level of advanced framing for any given project. Insulated headers, two stud corners and eliminating useless jack studs are easy. Going to 2' spacing with single top plates can be quite challenging.

Even with a high level of advanced framing, you are only reducing typical thermal bridging from around 25% to 18%. Not a big enough drop to take it to a high level in my opinion. Insulative sheathing on the other hand can have a much bigger effect on the R value part of the performance equation.

Eliminating thermal bridging should be a major goal for those building homes and interested in reducing monthly energy/environmental costs. However, focusing on blower door test results is much more likely to reduce energy costs than advanced framing. Air sealing is cheap compared to insulation and mechanical systems but has a much bigger effect on energy costs, durability, comfort, and reducing building safety dangers like backdrafting combustion appliances, garage fumes and soil gases.

Weve always used pre-cast concrete panels for basements and SIPS for above grade walls as a cost-competitive alternative to insulative sheathing mainly due to the reduced labor costs. On one of our upcoming homes we will be trying the new ZIP+R sheathing product for the walls. I think it will be a game changer for us.

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This post was edited by Renovator8 on Wed, Aug 7, 13 at 20:11

in my area, it is difficult to get frame carpenters
to to optimum value framing.
laying out studs 16"oc is standard, too much
'thinking' to change to 24" oc.
roof rafters have to fall directly on wall studs..
and most can't wrap their heads around it.

I've had more success in regular stick frame
with foam sheathing on the exterior of walls.
properly nailed, caulked & seams taped.
behind brick or furred out walls for siding
we use a foil faced foam sheathing.
behing stucco t&g.

and I have to say, in all fairness, that sometimes
it is difficult to get framers to do the foam sheathing
install properly. it all depends on the builder & if he
is willing to do more than code dictates.
code being the least you can legally build to,
but better building practices being the goal.

I like double top plates for higher insulation
values at edges of roof when doing insulation
on attic floor.

most in my area opt to foam insulate the roofline
to put ductwork & equipment in semi conditioned space.
while this is a more costly insulation, it covers
many building failures.
and studies have shown that unvented attics withstand
hurricane forces much better than vented attics.
some of the most common building failures include:
IC instead of ICAT recessed lights
oversized cuts for supply boxes, stove vents & bath fans.
thermal bypasses like shower units & fireplaces left
open in attic.

IMO one of the best efficiency upgrades
is to design the house with
ducts/equip inside the living space.
also invest in mid range
efficiency hvac equipment, mastic seal of duct system
and air sealing of house.

the latter is achieved more often than the former.
folks just don't understand the design of fur downs
for a/c ducts & designers & architects fail us in
not incorperating this in design of homes.

air sealing often falls to the homeowner to make sure
it is done, or to diy.

load calcs for hvac sizing, duct design & sizing are all
things that should be done prior to start of build.
info for build ...shgc & uvalues of windows, insulation
R-values, orientation, size of overhang should all be
provided for these calcs.
one thing that makes a big difference in sizing is the
tightness of the house. load calcs give 3 choices.
very leaky, average & tight..it makes a big difference
in sizing for a leaky house to a tight house.

if you nail down your details now, and get everyone
on the same page, you'll have a better chance at
an efficient house.

myself like the two posters above have experience
with numerous builds. efficiency is formost in the
projects we are involved with, not an afterthought.
glad to see that you are being proactive with your
build.

solid sheated plywood or osb on exterior of house
(or interior) makes for a stronger structure. its pretty
common in my hurricane area. as with adding foam
sheathing, door & windows have to be adjusted for
this thicker wall.

where are you located?

best of luck.

I have done both, but actually prefer a modified version of it. A 2x6 wall at 24" oc is no weaker than a 2x4 @ 16" oc.
At the end of the day, I have found if you do the details how they show them using metal header brackets to reduce framing, the cost of these are more than a stud, not mention longer time for install. My details typically include an insulated box header, king and jack studs as normal, double top plate and 24" oc 2x6. With a double top plate, they can place trusses where needed. It also gives more wood to anchor the truss hurricane clip into. My current home is ICF for hte house, but 2x6 "ove" for the garage walls. My fathers place we built last year we used 2x4 for the garage. My walls, at 24" are stronger than his are. They both have 1/2" osb on them.
Of course air sealing and thermal bridge reducing is a higher issue to me than 16" vs 24". As others have stated, go with exterior foam and your gain in thermal bridge reduction will be a lot higher. A wall assembly I like to use for a heating climate includes: 1/2" air tight drywall, little to no can lighting (yes!!! you can light a house without cans!!! better infact!) not even the so called air tight ones, blown in dense packed insulation in the walls (open cell spray foam if you feel like spending even more), 2x6 24" framing as said above, 1/2" ZIP sheathing, seams taped per install requirements (this places your air barrier on the exterior of your wall), 1.5-2" of XPS foam, 3/4" furring strips for air cavity, and cladding of choice. This is a proven and high performing wall system. You could take it to the next step and do double stud wall framing and eliminate the exterior foam, but you use interior floor space up. Of course do not forget about the basement or concrete slab (place 2" XPS there) and the roof. Air tight ceiling (I perfer to have them install drywall as normal and then spray foam an "attic seal" which is just foam around electrical penetrations, plumbing and tops of walls) and shoot an r60+ in the attic space.
Check with local power and heating companies. You may be able to get special rebates for building a higher performing house than code min. In our area we get about $6k back in rebates for building 5% above Energy Star 3.0. That will cover all or more of the building upgrades described above.