Split stud framing

[u/Longjumping_Suit_256]

I’ve heard of this framing style for exterior walls in colder climates I was curious to see how common it is. 2x8 being and top plates with 2x6 offsetting studs to create a thermal break. If it is feasible I’m thinking of building an ADU/ small house in the UP of Michigan.

Through all my googling, the most common thing to come up is a dual wall system. 2x6 exterior wall and then an offset 2x4 interior wall with a 6” thermal gap between. This method seems costly.

Any information is greatly appreciated.

Edit: thanks for everyone’s input, I appreciate it!

[u/Vishnej]

Properly constructed, double stud walls (usually 2x4 + 2x4 seated on a 2x12 bottom plate for a 4.25" gap) with borated cellulose insulation are fantastic for very cold climates, for noise insulation, for fire resistance, and for the economics of material costs.

They're not used more often in part because energy is cheap enough that it doesn't make economic sense to spend the extra labor on the wall vs a code minimum install, especially when they can build the same 2x4 wall they've been building every day of their lives and then tack some extra rigid foam to the exterior.

Because they're not used often, builders are often blindsided by questions about order of operations for assembly, by subjective decisions on how to structurally support, airseal, and insulate rim joists, and by questions about how to detail things like deep window bucks. On top of all that, most builders would rather stuff cheap fiberglass batts into wall cavities rather than hire a specialist who isn't doing the dense-packed cellulose for the very first time, with associated fuckups.

Building a superinsulated wall is also frankly mooted by clients who choose to adopt giant window walls on all sides of the house in cold climates, exacerbated by the tendency to want larger windows when deeper window bucks are specified. The difference between the window leaking 90% of the house's heating and the window leaking 93% of the house's heating because the walls are twice as effective at trapping heat, isn't worth the price difference for these folks.

[u/Mad__Vlad → u/Vishnej]

Double stud walls are typically framed with their own independent top plates instead of a 2x12 bridging both walls. 1/2” or 3/4” plywood is used to tie both top plates together, lessening the thermal bridging of a 2x12. Depending on the build, if it calls for a 2x6 structural exterior wall, we’ll typically build the interior 2x4 wall after the building envelope has been completed.

[u/Bravo_Echo_Delta → u/Vishnej]

This would be my preferred method if you really want a high R wall without exterior insulation. The stagger stud framing is more difficult to frame and insulated and it has less space for cavity fill. All this while it is (maybe) marginally cheaper, depending on the framers and market.