High Performance Wall Challenge: Double Stud Walls from Kolbert Building

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A little while ago, we told you about an Instagram challenge for the most high-performing wall that was practical to build.
We at ProTradeCraft decided to make animations of the four finalists.
This one comes from Ben Bogie, production manager, at Kolbert Building in Portland, Maine.
Ben’s wall begins with a foundation in the ground and some sort of floor. To keep it simple, we’re doing a slab on grade.
Kolbert Building uses the plastic under a slab to also isolate ther foundation from capillarity, but that’s a topic for another discussion.
They frame the outer wall like they would any other wall, except they use 2x4s.
Atop the wall a strip ofZIP System sheathing is nailed. This creates the perimeter air barrier strip.
Outside the wall, housewrap folds over that air barrier strip.
Roof framing sits atop the wall framing.
Now, they frame another wall inside the outer one. This wall has a single top plate, so it’s 1-½ inches shorter than the outer one. The ceiling air barrier sheathing is continued with the seams taped.
Crisscrossed 1x3 furring strips create a service cavity for running wires and PEX, if needed. They also eliminate truss uplift troubles and give drywallers a larger target for their screws.
The window openings are bridges with ¾ inch subfloor stips to provide a solid substrate for flashing the rough opening.
At the base of the wall outside, the sheathing is taped to the foundation for an air seal and the WRB overlaps the tape.
Furring strips go outside the WRB and a strip of cora-vent is installed at the base of them to keep bugs and other micro-varmits out.
Ben says that they install the WRB, split-release flashing tape, and cora vent before listing the wall to minimize ladder work.
Trim and siding go on just like a regular wall.
Baffles made from OSB and blocks are placed in each roof framing cavity to keep the THICK insulation where they want it.
Capping this highly insulated double stud wall.
There may be no R in wall, but there are more than 40 Rs in this assembly.
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[@DavinStewart]

YYYYEEEEESSSSS!!!! This video just blew my mind. I'm building a shed and these concepts are so far beyond me that my brain just exploded. Somebody get ahold of Matt Risinger. Also, nice sketchup work there.

[@johnjacobjinglehimerschmid3555]

He's got video's on double wall building all ready!

[@DaveDugdaleColorado]

You are a master of this illustrations.

[@ProTradeCraft]

Thank you.

[@rhd244]

Wow! This design is really good.

[@FrankReif]

Would love to have these models published on the 3D warehouse. I'd happily model to your model format and help get a library of assemblies for different climate zones and building uses.

[@nfettes1]

Great video, well done all around.

[@MrTooTechnical]

finally. the mouse resist wall. woohoo. kick ass

[@GeraldForsburg]

I just designed a home with a superinsulated wall like this - R-40 walls and R-60 ceiling.

[@Hermiel]

Love it! Keep 'em coming!

[@unionse7en]

great explanation and graphics. An improvement would be a better thermal break at the attic floor.

[@tatebraboy336]

Where do the framing nails go on the inside wall to keep it full supported while still decoupled??? There’s no nails on top plate or sides to keep the interior wall from wobbling

[@ProTradeCraft]

The top plate is nailed into the ceiling joists and the bottom plate is nailed into the floor.

[@meta2016]

He didn't correctly explain that, you would use scrap plywood the width of the cavity plus the total thickness of the wall framing, the interior wall and exterior wall would be strapped together every so often with the plywood scrap/strappings

[@maxmoran1683]

What would you recommended for the connection to a stick framed vaulted roof? Air barrier on the underside still?

[@SandmanUSAFA]

1) Thanks for the work, great vid! 2) Does the submitter also have perhaps a folder of jobsite photos or some assembly videos from one going up? 3) Is that big interstitial wall gap filled with a simple cellulose blown-in insulation like it looks in this illustration? 4) If that inner--stud wall does NOT attach or extend to the same height nor up to the truss, how do you hold it in place once plumb?

[@zackdreamcast]

It’s dense pack cellulose

[@meta2016]

He didn't mention that but you would use scrap plywood and connect the interior wall to exterior every so often

[@samuraydesign]

It would be nice to see this approach for 2-storey building.

[@MurDocInc]

kzbin.info/www/bejne/ZoHSf4Cwrap_rMk

[@Nova-m8d]

I see other videos where they have double wall construction and use 2x6 on both walls but that doesn't make any sense. The inside 2x4 exterior wall can be located at any distance needed for any insulation thickness. Double 2x6 walls are wasted money.

[@ProTradeCraft]

Agreed. It costs more, is heavier to lift, and takes space away from the insulation.One 2x6 wall may make sense for bearing purposes if it is a tall house...

[@nimblybimbly4002]

A whole nother discussion! 0:35

[@johnjacobjinglehimerschmid3555]

That's one I'd like to see.

[@nimblybimbly4002]

Do building codes in some jurisdictions allow an interior wall to not be connected to structure at the top?

[@johnjacobjinglehimerschmid3555]

Looks like the 1X3's when crossed would suppose there'd be a 1x3 parallel to outside wall ... would make up the 1.5 inch 2x4 height. So ... it would be affixed to the floor above.

[@dc-wp8oc]

You mention "truss uplift" in this video. What exactly is this and how is it addressed before, during or after construction? Like this style of presentation especially the drawings or illustrations.

[@ProTradeCraft]

Truss uplift is a bigger topic than a comment section, but wood moves and trusses are made of skinny wood. strapping the ceilings reduces the effects.

[@dc-wp8oc]

@@ProTradeCraft Maybe an idea for another video.

[@meta2016]

Basically the top cords of the truss changes length when the temperature changes Example when it's hot outside say 100° but you have your house ac set to 68° the upper truss cord grows in length (expanding/expands) because of the heat and the lower cord shrinks because it's cooler this causes the upper cord via the webbings to pull up on the lower cord.

[@thomasmeehan4060]

how is the interior wall anchored at the top of wall?

[@ProTradeCraft]

Nailed up through the top plate into the 1x strapping.

[@aldoogie824]

Are you going to feature the other final two?

[@ProTradeCraft]

I am. I'm just swamped with things to do. Thank you for your patience.

[@aldoogie824]

@@ProTradeCraft I got framers and insulation guys on the job site for months now just burning through my cash waiting for me to give them my wall assembly detail “I told you already, we’re waiting for the best one to come in any day now, just be patient, this thing will be worth the wait”.... I don’t care how long it takes, we’re not moving forward until this video gets posted. No pressure or anything.

[@Shadowtech2024]

What HERS rating would a house built this way get?

[@HotNoob]

what holds the interior wall up, since its not attached to the roof, and that outer vapour barrier better be good, cause if it fails in the slightest... rot galore.

[@ProTradeCraft]

Interior walls are nailed into the floor and ceiling. They are also connected to the exterior walls at every window and door opening. The outer layer, the green stuff on a ZIP panel is NIOT a vapor barrier, it is permeable to vapor, impermeable to liquid. I am guessing by your spelling of "vapour," that you are located in Canada. In very cold areas, vapor barriers are sometimes used on the INTERIOR, but in almost all climate zones, a vapor retarder, which allows drying to the inside, is a safer choice.

[@arendraifsnider2959]

@@ProTradeCraft Sorry, I must be missing where the interior wall is nailed to the ceiling since it only has a single top plate. Can you clarify that?

[@meta2016]

This wall technique allows for the wall to dry from either the inside or outside, as for connecting the two walls together they will use scrap plywood strapping every so often to connect the two walls

[@azgreg]

When's the next video in this series?

[@ProTradeCraft]

It is shoveling snow right now, but as soon as it is finished, it will dust itself off and publish itself. Soon.

[@azgreg]

@@ProTradeCraft Updates?

[@azgreg]

Looks like you've given up on this series.

[@bobmariano3731]

Do you have any videos on ICF foundations & builds ? ?

[@ProTradeCraft]

Unbelievably, we do not. Can you believe it?

[@Hermiel]

Where are the final two entries?

[@ProTradeCraft]

Working on it. In the meantime, watch Building Resilience.

[@Hermiel]

@@ProTradeCraft Copy that. Looking forward!

[@nbansal4732]

Seems easier and more robust to do continuous external air/water barrier, use Zip system on Risinger's "monopoly framing" and you can add some external polyiso too. The whole exterior would be one continuous barrier without relying on trades to "get it right".

[@ProTradeCraft]

There are many ways to build superinsulated walls. Often existing conditions make one option more attractive than another. People who hate foam sometimes like double studs or larsen trusses.

[@meta2016]

Matt Risinger is a corporate shill, better to talk to other HE home builders

[@jckclt]

Not sure why they didn't do external foam board since they did the firing strips

[@vanderumd11]

Strips so siding has no wall contact

[@meta2016]

No matter what way you build and insulate a modern house you will always want to have the air gap between the exterior siding and the house