Hi everyone! We're so thrilled that people have gotten to see this video and appreciate all of the thoughtful comments here! We were not expecting this video to get this kind of traction, but we're thrilled you're here! Check out the other videos on our Net Zero playlist here to see the foundation and basement building details as well. To address a couple of comments overall: We are a net zero builder, and we wanted to share our techniques that we use on a day-to-day basis to improve our homes energy efficiency, in Calgary, Alberta. We're always balancing using cost effective building techniques that improve energy efficiency, without impacting the overall constructionability. We like this system for exterior walls because framing out a wall with 2x4 studs, is something every framer knows how to do, and doesn't need specialty training to execute. The materials are also all readily available. Cost wise versus energy savings - the energy savings far outweigh the added costs of construction. Simply by exchanging one 2x6 wall for two 2x4 walls, we have only increased our lumber package by a small amount, and increased our framing labor marginally. We are now left with a wall system that is completely thermally broken, with substantially more insulation, that has very high constructionability. And, at the end of the day, we're making small changes to build a more energy efficient home. This one in particular is net zero. We'll also make a video going through the costs of this home in greater detail. Stay tuned for that! Our next video is coming out this Sunday! We'll be going through the Blower Door Test for this net zero home, and showing some of the extra steps we do to prepare there. Check that out to see how air tight we were able to get this net zero home!

It is not just the cost of the lumber. You have framing costs as well. And increased foundation basement floor roofing taxes for larger footprint etc. So please calculate entire costs and return on investment. Also be aware that there is no totally effective moisture and air barrier. You will get condensation wthin the wall structure.

We remodeled a home that was built exacting like this. It was about 10 years old. When we opened up an exterior wall the cellulose had settled between 10 to 12 inches at the top of the wall. I hope your stuff works better than theirs.

Your missed the labor cost to build the second wall in your 60% figures. You also didn’t mention extention jambs cost on windows and doors and that extra labor factored into the 60% cost.

I’m a home energy freak for years. The home I built for myself I used 2X6s with R19 batting . I often thought of doing exactly what you did on my outside walls so any plumbing and electrical would be in an interior wall by itself. Fantastic idea you have.

I was working with an old-timer in the early 1980's when he showed me that method. Back then nobody cared that much about energy efficiency but that was how they built walk in freezers. It makes for pretty deep window cells but does make for really high R-factors. Thanks for posting this very informative video.

While the insulating aspect is fascinating Having an open cavity from 1st to 2nd floor reminds me of balloon framing that was popular at one time. The problem is it was a chimney for fires. By not running your floor joists to the outer walls there is no containment between floors. I would imagine fire code would dictate fire stops installed in the chase areas to prevent this from happening regardless of fire retardant insulation.

Just looked at my local HD here in Calgary 🇨🇦 8' 2x4 - $3.98 × 2 = $7.96 8' 2x6 - $6.98 8' 2x8 - $13.22 8' 2x10 - $16.66 So, for a build where you are looking to maximize your exterior wall thickness and insulation, the double 2x4 exterior wall is a much less expensive option, even with the additional labor, AND it gives you a complete thermal break from inside to out. And again, just talking about the exterior walls here and not every wall in the building.

I dealt with the thermal bridging issue in a similar fasion. I used 8" timbers for the main timber framing utilizing post and beam construction . The inner and outer studs are installed parallel to the face and back of the main timbers. I installed the exterior 2x4" studs horizontal, and I installed 1x4" interior studs vertical. I Planked exterior using 1x12 pine for siding installed horizontal, boards with batons. Insulated with 5.5" inches of opposing layers of EPS foam board. R-5 per inch gives an R-28 wall. Opposing layers of foam board makes a quiet and well sealed wall. Cellulose has at best a 2.2 to 3.8 R value. But generally settles as much as 12"s over time. Settling reduces it's R value. As it settles it becomes more dense and R value suffers. The top of the wall cavity may have 6" to 12" of no insulation within a couple years. Though my 5.5" insulation is not R 40, I think a solid R-28 is pretty respectable. With the foam board between the studs the walls are dense and solid. I'm certain people are cringing, yet my comfort and cost to heat this home, in South Central Alaska confirms my design. Everyone who visited the site, or visits, remarks at how stout the post and beam construction seems to appear. Rolled right through our 7.2 earthquake like a Cadillac over a highway of down pillows. With triple pane windows we live quiet and cozy and cheap.

You should look at "T" stud. They're made in Canada. They come as 2x8 and 2x6. It is double studed like yours but has criss crossed dowels conecting them. They com either wood only or prefilled with insulation. R value of 25+. It would do the same with less labor...

Coming from an old retired carpenter I totally agree that your wall is way better than a 2x6 outside wall ..... I my self would even make the gap at least 5 or 6 inches ..... Nice video.

It looks like their isn't an effective fire block between the bottom half and top half of the wall. So fire could spread much faster.

I built a lake home in northern Wisconsin with double 2x4 studs but staggered them and used a standard 2x6 header for firebreak. We used blown in damp cellulose for insulation. That place is incredilby quiet and I believe we have a full R-22 wall instead of ending up with R-17 when using 2x6 and R-22 fiberglass. The damp cellulose packs a lot better than dry cellulose blown in, but you have to wait a few days for the moisture level to drop before covering. The damp stuff stays in place without the added net necessary for dry cellulose.

Very interesting approach. Thanks for sharing with the community.

In many places, code is still a single 2×4 wall. Thermal break is not usually part of code. The reason 2×6 walls are used is to attain the necessary R-value required by code. The 2×6 wall is the cheapest too. Now if you want cheaper than this double wall while maintaining the thermal break, use a single 2×4 and then completely sheet the exterior in rigid foam insulation.

I saw this demonstrated as a system at a NAHB convention about 28ish years ago. It seems so obvious and brilliant for cold climates. My sensei Russ was obsessed with energy efficiency. His house is a pair of earth sheltered domes, connected. Kind of genius.

1. Offset the inner and outer studs will slightly improve insulation. 2. Raised heel truss will allow the wall cavity to be open to the roof insulation such that any insulation settling will have a huge reservoir from the roof area, and still leave no uninsulated gaps. 3. Condensation/water is the biggest problem with highly insulated double wall. There are quite a number of things online on how to carefully deal with permeability and vapor and condensation. Anything else may be good for a while, but later be moldy and decay prone.

I love the double stud design! Very curious about your ceiling installation. Do you have a conditioned attic in this home? Insulation in the ceiling joists or roof rafters? Would love more details on this fascinating project

Thanks for the great video! It's great to see builders exploring options and sharing their experience around deep walls. In terms of options, have you experimented or reviewed other wall assembly types? ie 2x4 with outsilation?

I came into this video expecting something I’d really want to tear apart and dissect, but I really enjoyed this! Thanks very much!

Nice to see a Canadian Company revisiting the double wall system. We used this idea back in the early to mid 70's with great success. We actually lived in and owned a house with these type of 10" walls. This is getting closer to the Canadian building code changes coming in 2030. Now you need to work on fixing the thermal bridges at the top and bottom of the exterior walls and using an insulation like rock wool or spray in closed cell foam insulation to stop the gravitational settling that the lesser quality fiberglass insulations always do (except the paper backed pink stuff).

Three questions. How do you do fire blocking when necessary? How do you do the framing around window and door openings? How do you do top plates particularly where trusses or rafters intersect?

With thicker walls makes smaller rooms, this means that most people will want to build a wider foundation to compensate for the loss of room. So adding more concrete, sheeting, shingles and siding plus hardware I’m thinking the price of the studs will probably favour the 2x6. But I’m sure the gain in heat loss prevention would make up that difference in the long term. Definitely something to consider but certainly not a simple decision.

Great video. Short and to the POINT!! Perfect!

Thanks for the share! Look forward to seeing the cost breakdown. We've been looking at a similar cost:performance ratio to figure out what type of wall assembly works best for giving us that "bubble" in our Canadian winters. I'm not as cold out here in Nova Scotia, but we're still trying to get the best bang for buck. Having a "bubble" around the house, especially that thermal break, seems to be a great way to keep the money in your pocket over the long run.

If you're looking for a certain size room, the foundation has to be increased in size to accommodate the additional framing. That and the increased cost of more wall lumber and rafters which increases the cost substantially. Not to mention the added labor cost. Perhaps, if I were building the home myself, it may be worth the extra expense.

I built this design 35 yesrs ago with 12 invh heel height om the ranch we've living in. Works extremely well

Was working on a house from the 50s. It had 6" top and bottom plate with staggered 2x4 studs to each side of the wall. So 24" on each side to mount drywall. but it had less transfer of noise and temperature. All inside walls and exterior walls were done like that

Over the last fifty five years I have been in construction I have seen many new ideas being done. Each idea comes then goes, then comes again. Glad to see the merry go round of ideas still turning

Built ours with 2x6 24" OC BUT, we covered the exterior with 1" foil-faced Polyiso sheets and foil taped seams in a total package wrap of the walls and roof with no gaps. So we had a thermal barrier around the exterior so the studs would not allow pass-through of heat/cold. We covered the Polyiso with Zip siding and roofing, taped and sealed for a moisture/vapor barrier. We then had the interior spray foam insulated with 4.5 inches of foam. We only heat with a small wood stove and even at 40 below, the house is usually too warm if we keep the stove going. The siding is simple board/batten and the roof is metal on furring strips so we have an air gap between zip roofing and the metal.

I enjoyed your very informative video, and I am looking forward to the next one! Well done!

I designed my own version of this. 2x8 wall. Nice window sills. 2 inch gap and spray foam which gives my exterior walls a total of R35. Very cost effective. Cheers.

It's great to see a channel like this geared towards Canadian prairie climates. I follow Risinger and similar channels but I think you're the first I see in AB!

Great idea. Great return for your investment. I lived in a condo and they did this with the common wall between units. They were concerned with noise transmission. Never heard the neighbors or their kids running around.

This method not only provides a better thermal barrier ,it also gives a superior s.t.f. sound transmission factor. So.. warmer in the winter..cooler in the summer.. and quieter year rough. A win/win situation.

I built recording studio walls this way for sound proofing. We hung a double layer of sheetrock on one side to shift the resonant frequencies of the walls away from each other. Worked great!

I like this wall assembly anywhere that you have detached homes. I live in a big city in a narrow row house (terraced home), and it would be unfortunate to lose a few inches on each side if I were to remodel my home and add insulation. But if you have a few meters around your house on all sides then I think it makes more sense to build double walls with a proper thermal break. If i were doing this, instead of using cellulose, I would build with separate layers of insulation to make it easy to run mechanicals through the gap between the 2x4 walls. I think that’s a huge benefit of this wall assembly. You can run plumbing and electrical in between the 2x4 walls without drilling into studs. I think the ideal system would be to spray-foam the outer wall and then fill the cavity and also the inner wall with mineral wool batt insulation. Yes, that would be more expensive than cellulose, but it would perform well, and I think it would make it easier to run, fix or remodel mechanicals. The sound dampening on that system would be amazing.

He didnt mention it, but plumbers love it too. 10" of space to hide a lot plumbing and less chance of nailing into pipes.

Thanks for the information, great tips for New builds.

I built a double wall construction but I off set the inside wall studding 12 inch which gave me less thermo bridging except the windows and doors I kept in line with the outside

What about just doing a layer of rigid foam on the sheathing for a thermal break? Thanks for the vid

I wonder why the studs are lined up on both walls and not staggered to the best distance on inside and outside, say 16" o.c. from inside corner for Gyp. Bd. and 16" o.c. from exterior corner for siding on outside. Is there a reason they are lined up?

Also, in the late 70s a construction company built 12 inch walls, call an envelope of house. The outside wall was 204 with the insulation going up and down and it was a 3 1/2 inch gap with the insulation laying on edge, filling the opening, and then another 2 x 4 wall on the inside. The vapor barrier was on the outside of the inside wall to try to combat a moisture problem. A number of years later some of those houses had been remodeled and they found mold and several of the walls. I would recommend anybody looking to try something like that to check with a current engineer or architect for advice on that. Also something I forgot, the space between my inside wall, and my outside stud wall was a perfect place to run the wiring without having to drill through the studs and I did not have to worry about hanging a picture or anything on the wall and hitting the electrical wiring because it was a full 3 1/2 inches away from the exterior of the house.

Ive been a builder my entire life, and I am very impressed by this level of care in design and build!

LABOR LABOR LABOR - who cares what the stud costs. Let's see the window buck detail on this 10-inch wall.

Man you need to look in to T-Studs, for what your doing the cost would most likely me less and with something like Zip-R you could build a much better walls with less labor and material cost.

This is a common technique for building sound proof walls in recording studios. Very effective!

Interesting....and easy to understand. tHanks for the video

If the 3" gap runs completely open from the first floor past the second floor and into the attic, does that cause a potential fire hazard since there's no firebreak at the top plate anymore?

More lumber makes more waste and more lumber mean more labor to install. Interested to see a breakdown of all the costs.

Makes sense, and I know of a few people who live north in Canada who have double walls, and swear by them. The only thing that worries me is that one of the "benefits" of 2x6 walls was that the lumber is better quality. Getting any 2x4 lumber these days that isn't a joke is nearly impossible. I realize that lumber quality and availability varies a lot by region, but where I am the quality increases markedly in the larger dimensions. Then the other question is whether 2x6 with foam on the outside for the break, is easier to build and just as efficient for less loss of floor area in tighter urban floor plans.

We have some commercial buildings that use this method in noisy areas such as along train tracks and hiways. Excellent for sound.

What about just adding exterior insulation with the sheathing? Like Zip-R panels, or adding Poly-Iso or EPS panels then regular sheathing.

Maybe use a 2*10 top and bottom plate and stagger the 2*4 studs from outside to inside.

we had the dense pack in the apartments we used to manage, very quiet neighbors, and cheap utilities.

Reading some of the comments, it's correct you need fire blocking. Also you need blocking for your plywood 9 ft wall 10 ft wall 12 ft wall something to look at.

In predominantly heating regions (northern climates) you need 1/3 of the wall's effective R value as exterior insulation. The higher the wall R value, the colder your sheathing will be because the heat from the interior can't reach it. During the winter the warmer moist interior air will condense on the back side of the sheathing and cause mold and rot. No vapor barrier or vapor retarder can prevent that. A wall assembly with R10 exterior installation and R20 interior insulation would be higher performance due to the thermal breaking from the exterior insulation.

The cost makes sense if you are building with 2x4x8 where it’s $3.98 vs 2x6x8 which is $6.23 in my area local Home Depot New Jersey. But when you go up to 2x4x 10 and 2x6x10, the cost is $1.29 difference. $6.54 and $7.82

And, If you do this (slightly modified/a lighter version) on interior walls you get soundproofing, too, so. Great info.

You need to consider dew point. If its 75 inside and 20 degrees outside there will be a gradient of descending temperature in your wall. At some point there will be a dew point where the warmer more humid air crosses the temp threshold where the air temp can no longer hold the water as vapor and it will condense. I build with 2/6 studs and put two layers of roxul comfort board 80 seams staggered. This helps to put the dew point in a non organic layer and keeps the wood sheathing warm to avoid rot. When you net large cavities you need to net the face and net back to make isolated pockets otherwise you keep blowing the Cellulose down the wall and dont get and even pack.

The second story system creates a fire chimney

It would be interesting to see a side-by-side total wall R value and cost comparison of 2x6 wall vs double 2x4 wall with gap vs 2x4 wall with exterior insulation vs 2x6 wall with exterior insulation.

I have been building customs ...all waterfront....for over 40 yrs. I saw this method back in the early 80s when passive solar was popular. Other costs to consider are window extensions , mold issues and roof framing. I will take my homes with soy based foam insulation, Pellar windows and Hybrid HVAC with Heatpump hot water. Only 2 of the last 16 homes l built have been sold by original owners.... to move closer to their kids!

I would suggest that you also explore exterior continuous insulation in combination with a rain screen, my favorite wall assembly. The rain screen is really bulletproof in terms of waterproofing and the exterior insulation can be varied in thickness to achieve the desired performance. One could even explore (and analyze cost) to do no cavity insulation at all and save the working step and only provide exterior continuous insulation. An additional 1-2” would most likely replace the cavity insulation. this is because the studs degrade the thermal performance so much. The exterior continuous insulation can also very nicely line up with an exterior insulation at the concrete base wall or slab on grade. Food for thought…..

Err that gap around the second floor might violate firebreak codes

Is the second floor truss only sitting on a single plate 2x4 wall(your inner layer of the exterior wall) I am trying to understand if the load is transferring . If the inner and outer exterior wall are not tied together and the second floor is only on the inner wall then is your max load rating based on 2x4?

I don’t know if I want to loose so much interior space. Like to support your channel

Interesting , Thank You .

The second floor is placed on is single top plate and a wall that has no sheer strength. Is that approved by your engineer? And how about extra labour costs?

Why not stagger the studs on the two walls? You could decrease the distance between the parallel walls and still maintain a wider thermal break between them. With the studs in line with each other, and then insulate the double wall, the R value in the narrow spot between the parallel studs is less than the spaces between them. With the studs staggered, and then insulated, the R value is almost constant along the wall. The staggered studs don't change how windows and doorways get framed in.

We did our 1990 built 2x4 house. Add extra interior 2x4 wall and now at r 24 walls. Only thing different is offsetting the studs and I had to rewire walls, but that's ok I have completely changed whole inside of house,anyway. Can't hear anything outside as well to the r value

I have been using a staggered 2X4 stud outer wall construction with an 2X8 cap and bottom plate. There is a stud every 12”. One stud on the outer side and 12” to a stud on the inner wall. Years ago I used standard 2X4 top and bottom plates on both walls but I prefer to tie them together now with the 2X8 plates.

But there is an extra cost in foundation/slab? It has to accommodate the walls to maintain the square footage inside the home. With additional cost of 2 by 4, are the energy costs substantial to outweigh material costs? Is the warmth/cooling of the home offer significantly more comfort with a double wall system?

I like the Double Stud Wall! Are you using any exterior insulation? If no exterior insulation and only depending on wall thickness, how does this affect the exterior sheathing getting cold and causing condensation? It looks like you are not using an air-tight membrane on the inside to prevent moisture from moving from inside to cold outside. How does this work?

Wow... This is actually what I have drawings and plans for. Except my offsets are different and no second floor. So my ceiling and trusses are separated. ❤

Also to achieve certain dimensions of a room you would need to have a bigger foundation which is also more labor cost with more concrete.

Two questions: Could you use 2x3s on the inside? How would this compare to a 2x6 wall sheathed with Zip-R?

I think its a good way to get better sound isolation as well as added comfort but you also need to look at the whole assembly like getting better windows, thicker insulation not to mention the added labor cost of an inside 2 x 4 wall. Depending on cost of construction in your area, return on investment (energy savings vs cost) might take a while also. It would be interesting to know by how much resale value is affected too.

This double-stud wall is standard practice in Denmark and has been for decades. Why is there such a large gap between the exterior sheet goods? Do you seal it? Air movement drops the R-value of any structure.

Well done. That's the best possible way to build super insulation.

In my house we separated the 2 studs with 1 inch polystyrene, then blew in cellulose behind it and put in fiberglass batts in the inside wall. Seems to work pretty well.

Before jumping into this, do comparisons for windows and doors. I was going to do a 2x8 wall but the doors were considerably more money. Also consider 2x6 walls at 19.2 on center and use spray foam insulation.

Smart tips, thx!

Very nice. Great thinking outside the box. I may incorporate Sorensen's system into my future outbuilding/workshop - the minimum extra investment in studs & insulation will pay for itself in heating cost savings.

I think they mean better value due to lower utility bills that will eventually pay for the extra cost of two walls. Been out of the construction game for 20 years, so not sure how many are using 2x6 walls, let alone this. Granted it would be just the outside walls, but still going to add cost and you’d be losing some square footage, especially with a 7” gap along with the 3 1/2” for the second 2by, that almost a square foot, times the lineal feet of the house.

What happens when that blown in cellulose settles and now there's an air gap at the top?

I realize that in many areas builders have to comply with local building codes so rough framing material might be difficult to get approved. Keep in mind rough sawn lumber is perfect for double wall construction. Make sure it's kiln dried or better, air dried. If one must adhere to the cutesy polished and planed approved 2 x 4's then outside walls can be 24 O/C and second wall 16 O/C so 1/2 in. rock can be used. Also, if there is no second floor, what's wrong with using 2 x 3's for the second wall? Or, no load second wall could be rough sawn. All interior waslls such as bathroom, kitchen, bedrooms and living room walls can revert back to conventional 2 x 4.

In my experience since late '70s, super insulation is the best energy buy and by a substantial margin.

As a Firefighter that has battled balloon framing house fires in the past, how do you stop the chimney effect? I see you do have fire breaks on each 2x4 wall system, but that 3 inch gap is wide open and prone to fire extension.

You would still have structural framing outside of the insulation. Why not do insulation on the exterior of the exterior wall? That would protect your wall system and still not have thermal breaks

What about the top & bottom plate, assuming your gonna have to use 2x10 pt on the bottom & doubled up 2x10 on the top so while the studs dont cost much more the plates do plus increased labor for nailing in 2x as many studs. Still worth it in my opinion but at a certain point its gonna approach the price point that warrants investingating icf.

I liked your video and here is why. I worked some construction after high school while going to college. I’ve since built two houses for myself and agree with your concept. The first house I built with double 2 x 4 walls. The second wall was approximately 1/4 inch inside the outside wall. I off set the studs and insulated both with fiberglass insulation. Between the top plates and bottom plates I put sill seal on edge for a thermal break as well where the cripples and studs were at a door or window opening. I then framed those rough openings with 1/2 or 3/4 inch plywood for strength. My second house I was talked into building with 2 x 6 studs. I am so mad at myself for getting pursued to use 2 x 6 studs and vinyl siding. The insulation and sound barrier is terrible. If . . . I ever build again it will be a double 2 x 4 wall building. My first house heated for almost nothing I. Wisconsin. The 2 x 6 house is terrible to heat.

Did you take into consideration the modifications to the concrete foundation to accommodate the new wall structure as well as increase/ loss in square footage of 10" walls instead of 6.5" walls?

2x4 cost $3.5, 2x6 cost $5.5, so the double 2x4 wall would be $1.5 more per stud…

Staggered 2X4 (with 3" thermal break) studs for extra sound deadening, if needed. Rock wool on the outer and Pink insulation on the inside.

Unfortunately i have a double wall cabin, logs on one side and 2×4 insulated wall on the inside. It is very good and easy to meet the R 21 or higher installation requirements. Unfortunately, because of the way the walls are it is impossible to keep mice out, and insects and even a snake or 2. You would really need to build with this in mind.

T Studs!

Did you get an engineer to stamp these plans?

looks great!

You make great videos, sir. Builder here with 30 years in the industry. I have some bad news. 1) All cellulose wall fill settles, even dense pack. I use a thermal imager to inspect homes and it's pretty obvious. The only folks who say it doesn't settle are those that want to sell it to you. Experience tells me otherwise. 2) The house shown in this video (as framed) will not meet fire code in most jurisdictions (at least here in the US). Fire is required to be contained to each floor, and you do not have this with this framing type. If the insulation can flow directly form the second floor down to the first floor walls, so will fire. 3) Framing with double 2x4 construction has some draw backs (although we did it for years before the updated model energy code requirements). construction