I got more out of this one video than I did from dozens and dozens of other videos. The price breaks are fantastic! You just saved me days of work. Please do more.

I could be wrong, since there are so many different materials involved, but I think the double wall system also allows for more acoustic insulation. That may be a consideration for some people, particularly in an urban or busy suburban area.

Great stuff as always. Double walls also provide a huge reduction in sound transmission for those in noisy neighborhoods. If maximum thermal efficiency is the goal, then double walls are practically impossible to beat. However... the labor costs are a HUGE factor here. The cost to install exterior EPS/XPS will be drastically cheaper than having a crew frame out double walls and the extra details for fenestrations. And for most areas of the country, the difference between R40 (R21 cavity + 4" of rigid foam) and R60 might not even be noticeable. You'd probably be better off putting that extra money into upgraded windows and doors. Building double walls with double-pane windows would be pretty pointless, for example.

Neat stuff! We added 20 inches of insulation outside our log cabin, and to avoid the 'tunnel effect' out of the existing windows, we flared out the window openings horizontally at 45 degrees. The very thick walls then don't block your view!

I haven't watched any other of your videos but this single handedly caused me to subscribe and and see what else you got. Absolutely amazing video.

I'm totally sold on the double wall design. At the cost is daunting. I have to pay for it as I go. I don't have any kind of a construction loan. And I'm on disability so it's limited funds every month.. my idea was to put up a steel building, like a pole barn, and then frame up a house on the inside. Because I can do that out of the weather. And I can also leave a big enough walkway all the way around for maintenance on the inside of the pole barn. Not your typical construction project LOL. But doing it that way it gets me out of the weather, and I can put it together one room or wall at a time.

This is some of the best and most concise advice I’ve found online. Very helpful work here sir.

Outstanding! Thank you for the clarity of presentation, the walkthrough on the details and the cost breakdown.

I was able to understand everything in this video thanks to your vocabulary and delivery of information. This video is incredible! Great job

Well done! I built in1986 , staggered 2x4 stud walls 5” apart with 2 r19 fiberglass batts. 1 disadvantage is if or when mice get into the wall cavity they can travel freely. Otherwise I would do it again!

Great video love the density of information here, as well as great explanations on issues with the double wall system, and why they exist. Regarding the 27% increase in material cost however, the amount of cost for labor will be significantly higher then the exterior insulation option, As that requires no special planning, education or oversight of the workers. I will say that, at least theoretically, the performance of this double wall can vastly exceeded that assembly, But I think it’s gonna be roughly a tie cost wise.

Great video. Detailed explanation, quick, to the point. Thank you.

Interesting presentation, thank you. Also my compliments on your details and thorough walk-through.

I would love a video on leaving rafters exposed and insulating outside of the roof. We haven't figured out best way or a way we like yet. Being able to leave rafters exposed with roof board saves finishing money.

Great video, I'm looking to build a home in Calgary in a few years so this was insightful. I will be watching more

Wow! What an awesome video! Thanks so much for sharing your expertise! It’s given me a lot to think about for when I start the build on my lot here in Texas! 🤠

Love the content! Best explained engineer KZfaq channel I wish you would’ve added to this video how to do the roof/ceiling installation detail design

I was warm and cozy just watching this video.

I liked the double top plate detail that leaves the insulation cavity all the way floor to ceiling. Nice.

You know what I would love to see you do? A similar video on the all-out best wall assembly you can imagine, disregarding budget. Joe Lstiburek has a brief mention of the "institutional wall" but really doesn't go into details. I'm curious what something like that would look like. Basically infinite budget, but using actual building materials (no stuffing theoretical aerogel in the wall or something like that).

You answered all of my questions about windows and building science (i.e. how is the water management addressed at the bottom of windows to prevent moisture from entering the house.) and I like the price breakdown of the different wall assembly options.

Incredible content! Thanks so much.

this is a great video with clear explanations and great illustrations/ cost basis. would love to see more

I was building one of double wall house. Same idea but just regular vapor barrier (polyethylene)inside and regular membrane outside. Wood siding. Blown in cellulose insulation. So many moments about moisture removal weren't addressed a way video suggest. But it has continued insulation through gap between wall and ventilation in attic, so in theory moisture can get out this way, not horizontally, but vertically.

We have worked with both double wall and exterior Ci. And I would agree with your assessment in terms of cost. Another benefit of a DSW is that at least from the exterior is that flashing and finishing while extremely important to do correctly is quite simple and familiar to most trades.

I’d be curious to know how the cost of this compares to ICF?

Excellent video brother !!!!

Excellent details!

Great video. I appreciate the detailed wall assembly diagrams. The pace, visuals, explanations, all good. Question: Do you use standard sized outlet boxes or a smaller box to fit into the service cavity depth?

Amazing!! Thank you. Subscribed

Great job. I've been looking at 2x6 24 OC walls with Zip and rigid wood fiber insulation on the exterior but now I'm looking at double stud walls again. So many choices and so hard to decide.

Amazing information and presentation. I subbed after your vid on vapor barriers being used incorrectly. Your channel has an in credible amount of informative videos and it is going to get big. How would you go about insulating a timber frame home with fully exposed interior framing (posts, beams, bracing, rafters etc)? Structural insulated panels (SIPs) over the outside of the timber frame seems to be the standard, but I don't see many references to SIPs outside of that use case. SIPS seemed to be a hot topic about 15 years ago as the new wiz-bang super-insulation solution but I wonder if there are vapor problems with OSB glued to rigid foam on both sides and why they don't seem to be common? How would you tackle a timber frame?

Labor comparison would be great!

Great, informative video mate. Been designing my off grid home for over a year and the insulation part has been a nightmare. Prices for exterior insulation are near highway robbery.

Thanks so much for the excellent details on this and the cost comparison. I'm interested in discussing a project and filled out the form on your web-site.

Very nice! One thought I'd like to run by you is regarding the windows. Living near a major airport, I've seen some applications where two dual pain windows are installed, one behind the other. The deep walls in your application look like a perfect fit for this, but I was wondering what your thought is on it? Thank you kindly

Wonderful video and amazing diagrams. Very clear and simple to understand. How does using something like Zip R-9 and 2x6 wall compare to a double wall assembly? Do you have a sense of where it would be as cost comparison?

Great video! Thank you. I’m also curious about the comparison to insulated CMU systems like comfort block or Omni block.

Thank you for your thorough explanation. My concern is finding tradespeople to do the work exceptionally well at an affordable rate. It would be interesting to know how many years the return on investment would be. It seems the more innovative ideas in reducing electricity costs the more the power companies raise their prices. One must factor in the added increase in power in the ROI.

If i was building a double wall assembly, which i always thought of. There would be NO insulation between the interior wall stud, and the vapour barrier would be behind the interior wall. That reduce the potential of hole and leak in the vapour barrier caused by simple things like hangers, frame hooks, electrician, plumber etc... it would leave 2.5 or 3.5inches to run utilities, to install blocking, to hang stuff without perforating the vapour barrier

We use square notched timber frames. Window and door bays get spray foam and the bays next to them. The doors and windows get thermal breaks not thermal gaps around them. Usually zip sheating and mineral wool. The timber frame actually saves money on labor and lumber. The mineral wool in my masonry north wall and under slab was expensive. Building a passive solar earthship like Goldie and Matt's but no berm or tires. Plus their framing wasn't well thought out and I needed more roof pitch. I need 70 psf snow loads and 6 foot frost depths also. We use glulam 2x10's or 12's for beams. At 50-75$ for 16 foot beam and can make longer. Lvl need too much lateral bracing. A.I. really helps with cost and design considerations. Sure you have seen how flimsy lvl can be. Which glulam beams allow for 2x4 or less on the flats for double stud walls since not structural. Price goes up on wood every time it gets milled down and more wood stamps cost money too. But if you don't have local lumber mills the price for timber frame jumps. As the cost of shipping increases. It's why we use local masonry material and timbers. Right now shipping on rock and stone cost as much as the rock and stone. 800$ for 40 tons cost 800$ to be dropped on site. We do a lot of masonry work. Why give the cement company the money we could get for labor. We build a lot of A frames and skillion designs. I see where the double studs would be better like earth quake zones. If I build a walk in cooler I will use double studs for sure. Because hvac equipment hanging and on top of them. Set of framing for equipment and one for structure. Minimize the vibrations.

great details

Loved the video, there’s so much great information. Would this be something we could use in a state like Texas with higher humidity and heat?

Great video!!! Very informative. I wonder if you can do a similar video taking into account the cost of labor (even if it's just the cost of labor in your immediate area, just for comparison) and compare the single wall with exterior insulation, to this double wall system, to a SIP wall system, ICFs systems and perhaps even a HempCrete with Just BioFiber System. Even if you didn't go into all the details as thorough as what this video has, it would be tremendously informative for anyone looking to build a new house to see what the ACTUAL cost of a wall system per square foot is. Again, even if you compare it only in your area, at least, people can gauge apples to apples in one area. They can just do calculations for their areas afterwards.

It'll be interesting to see your comparison of the T-stud or thermal stud wall assembly.

i did precast wall with styrofoam as the bottom mold. It got me 4" of styrofoam all around my house and another 4 inches of concrete. I feel the materials are a bit more expensive than wood, but my walls went up in one day and are made in a factory so far less labor mistakes.

I'm so glad I stumbled upon this video. Consise, up to the point and covering all details. Subsribed. One note- the l double stud wall will be more labor intensive, would be nice to get a rough idea of increase in man hours.

Excellent tutorial. Much Appreciatted.

Thanks for the additional details and process. I've been looking at how to do this on the cheap, especially as we're just doing overbuilt, and I'm doing the labour myself, so I don't mind the extra nuance of making sure we just do it right the first time, and have something that just insanely outperforms at a very modest price bump. Plus, with the way operating costs are going, it seems to make so much more sense to crush it at the onset, and see your savings pay off over time. Who doesn't want to heat an entire space with a small space heater? =p LOL

I wish we could get this quality of design and content to help with building in hot and humid climates like 1A.

Loving this channel about to build in Fairbanks alaska

For the people living in the US this will of course make your house hurricane-proof as well, which is a nice side-benefit. As a person living in Sweden the shoddy building standards in the US honestly amazes me, triple-glazed windows here are standard, our house is 16 years old now and has triple-glazed windows all-around, proper insulation and a ground-source heat pump, something only a fraction of all the new homes in the US seemingly have. Seems very short-sighted since it saves you so much money in the long run.

What if you did precast concrete walls .There's a company where I am in NC that gets R 22 from their walls .I'm thinking basement and first floor.

What about fire block requirements? Do you need to do anything else? What about tall walls? Can I use this with stucco?

I have an idea for a video if you are intrigued by my question: What would be the optimal way to blend high performance wall design with low frequency acoustic absorption? I would think would would need to move the air sealing barrier further into the cavity, and keep an porous membrane as the interior finishing. Obvious it wouldnt need to be the whole wall assembly - but there must be a good tradeoff to make. Regards - Home theatre/ Hifi enthusiasts everywhere.

Would the ZIP system be an option for the exterior?

What are your thoughts on using a Zip (R6) sheathing instead of the wrap and plywood if building a home in Climate Zone 3 (northern Oklahoma)? We run AC about 90% of the year and turn the heat on maybe 5% of the year. Big fan of your videos… thank you.

I believe that using 4inch poly iso, Zip R 12 sheathing and an r16 2x6 wall will be the cheapest option to get r 53. If your using poly iso as an owner you should look for reclaimed 4 inch poly iso at about $20-$25 a sheet.

05:00 - Could you treat the OSB with some anti-fungus to make it a useable solution?

You leave the underside of the window frame open to allow any moisture that may penetrate the primary seal around the window to drain out to the exterior, but doesn’t this gap (free of insulation) defeat the purpose of using triple glazed windows and generate a condensation issue? Wouldn’t it be wiser to spend greater efforts eliminating the risk of water penetration in the first place, and filling the gap around the window frame with a closed cell foam insulation? Would like to hear your thoughts on this issue.

How about 2x4 covered by 3" tight foam board then the covering, and drywall inside (with or without blown insulation)

Gtreat video. Would the labor not be × 2 , because building 2 walls ?

Seeing that you're in Oregon, I'm curious if you've had any contact with the people at BCIT? They would have some interesting input.

maybe consider "celit" as a wheather proof sheating on the outside. or using an extra rigid wood fiber insulation board on the outside. this olaso helps with condesation problems.

Can you speak to the labor cost between double stud and double outer layer rock wool? Seems like you might end up saving money on labor and window products with ridged rock wool. Also, if you’re going past R40 on the walls.....do you need to?

Even on an R-20 wall most of the energy loss occurs at the windows and doors. Upgrade them and make them smaller for real energy savings. Energy analysis will identify when it makes sense to upgrade the R-value of the walls.

Does all of this apply to fiber glass? One would think it naturally more water resistant. Im betting labor costs equalizes all of these methods quite a bit too.

Nice!

On thick walls using a pair of windows one on the exterior and 1 on the interior seems like a nice solution. Has anyone done this with success?

Since ZIP is based on OSB, would you not recommend using ZIP with a double stud (12") wall assembly?

How do you meet the electrical code requirements for wires to be recessed back from the face of studs in order to avoid being punctured by drywall screws when using 2x3 wood furring on edge?

Are you incorporating any of the Zip R sheathing in your designs?

How do you guarantee that the installers won't leave any gaps in the air barriers or flashing? This method is dependent on getting those details perfect.

Wouldn't the staggered studs make batt insulation super easy too? The batts would overlap and you could run electrical conduits between the inside and outside framing.

The cost of this breaks down alright if you've got the money. I'm really curious as to the cost of repair however. Someone with a handheld drywall saw can poke thru that vapor barrier inside. and if you live somewhere with hurricanes. the outer wall could easily be hit and damaged with debris. again damaging the vapor barriers. Not much you can do when your house gets wacked with debris and you've got 7 more hours of whirling rain and wind to go. basically blowing it into the damaged area. Cost of repair is very important to me.

So for a build in Yukon, i could do R90 Rockwool

Do you think it would be bad thermally speaking to use a 2x10 plate wjth offset 2' o/c 2x4 walls staggered?

Our builds (cabin first, house later) are up against native forest which is susceptible to fires. I want steel or fibre cement cladding and galvanised steel spacers to hang the cladding off of, and some kind of heat proof insulation on the outside as a priority no matter what happens on the inside. Cannot get rockwool here, sadly. I suspect glass fibre would melt if temps extreme enough and only delay the catastrophe. Am I screwed or is there another option?

I’d love to see the cost calculated with labor and materials added… Just in his location, All the additional requirements in the specs cannot be compared apples to apples .

It may cost more for prep longer roof overhang than the money you save . I'll stay using pir

If we design a wall with R40, how efficient do the windows need to be ? window efficiency will be critical to increase wall R value.

Would it be possible to do a double walk assembly with metal siding?

I don't know when I will ever have the chance to build a house, but this information is still very interesting. Currently, I'm living in about as low performance of a house as possible,...still, I can dream. One concern I would have with building walls as described here is that in the future, people would be unlikely to take proper precautions during any repairs or remodeling. Even with a 1.5 inch service cavity present, would the next person not end up popping holes in the vapor barrier to install new light switches or receptacles in standard electrical boxes?

What if you used aircrete with this? 🤔

How are roofs insulated in double wall buildings?

I am going to be building in Maine and me and my Wife will be building it with an extra short term time to time helper. What about using Zip Systems Sheathing as it has a WRB weather resisting barrier (instead of 5/8 inch CDX) and with the off-set of the 2 x 4's and using Rock wool Batts with an other off-set grid pattern and or using your method of Dense packed blown in insulation and the added rain screen of 1 x3 prior to the exterior siding??? Reason why I ask about using Zip System was because it already has a WRB and 2x6 24 OC, *Note I am going to be installing an ERV for air circulation... I like your approach to save money and better insulation on a double walls... Thank you Liked#41 N Subscribed!!!

wouldn't it just be easier to put the insulation layer on the outside of the weather barrier to not worry about any of this?

How would this compare with ICF builds?

Who cut the trim on that window @2:24!?

What is the cost impact of a larger foundation if you need to maintain a minimum interior size footprint. Also, can you provide any insight into how this transitions to an insulated riof with conditioned attic space, continuity of your barriers and ecternally attached eaves? Awesome video BTW showing multiple ways to achieve outcomes.

Holly crap! I can build a double wall R60 blind 😂❤

I designed an built my house starting at 25 yrs old after reading Mother earth news and everything I could find on super insulating and the local building codes for guess 5 ish years, I am a millwright so the drafting, building ect... was something I was comfortable with, also I live in Canada which is very dry in winter with short summers, the foundation is 24 inch thick cement with a floating cement pad sitting on 8 inchs of foam with vapour barrier , the walls are typical 6 inch studs ,outside plywood, tar,papered , then flagstone, they have firestops,insulated,then vapour barrier, then 3 inch airgap , then built another wall 2/4 with firestops holding the electrical , insulated , vapour barrier , drywall , took 10 years to build 2 summers were digging the foundation by hand , it's 2 1/2 storys and about 3000 sq ft , the roof is trussed an comes out to r 60 , the walls r40 , half the house has a crawlspace, insulated and vapour barrier where the plumbing ect... are under the kitchen,bathroom area , the windows are glazed double pane, I think the outside walls breath through the tar paper and cement somewhat and the inside walls I dunno, so far no mold , unless your really anal and seal all the electrical outlets an stuff your going to have air movement , also you have to consider the dewpoint in the wall, where it is, mine is on the outside face of the vapour barrier on the outside wall that breaths, your wall is solid insulation so ? third of the way in I dunno something like that though, finished this house 35 years ago an have no regrets, some things with what is available today I would probably change , mostly the mechanical it has come a long way , I used pink fiberglass insulation today would use that green steel stuff that doesn't burn and is sound deadening, used that in my workshop an it's good stuff but wasn't made when I built the house, the house is very slow to change temp and in the winter if it's sunny will heat itself , it has heavy thinsulate curtains that keep cold/heat out/in, dunno what it would cost to build today i'm guessing alot, the inside walls are fully framed with headers ect... you could remove the outside framing an still have a house as they are framed today, anyone building their own house um if you want to save some miserable work hire someone to do the drywall because that really sucks, aside from that i'm pushing 70 and the work was worth the effort my wife of 49 years an I love it an would never move unless forced by old age. my 2 cents

Lots of commenters below have lots of excuses why double-stud walls can't work or aren't practical. My wife and I designed and built a super-insulated, off-grid solar home some fifteen years ago., here in central British Columbia, Canada. We can hit plus 40C in summer and minus 40C in winter, so a properly insulated home is obviously necessary. We have R48 in the walls, R36 underfoot and R68 overhead. The house is heated by both solar and a small wood cook-stove. We burn 1.25 cords of firewood a year, whereas all our friends and neighbours burn 8 - 12 cords. They laughed when they saw us building our unusual home, but they don't laugh any more. There are two kinds of people: those who like to talk, and those who like to do. We made it happen. Less talk, fewer excuses, more action.

have you any experience in how contractors really make sure everything is airtight? also do the outside insulation panels require tripple pane windows too? if i have a design that is standard 2x6 can you change it into the double studd walls for south carolina requirements?

At R-20, you have reduced heat flow between surfaces by 96%. This video is all about going after that 4% difference from R-20 to the "ideal". Look for ways to minimize thermal bridging and forget about the rest. IMHO.

So, my bone to pick with this video is that he doesn't seem to account for the cost of the increased size of the structure to compensate for the extreme wall thickness. I would imagine that would eat significantly into the cost efficency of the wall assembly. If you add an extra six inches of wall all the way around a 40x40 structure, that is approximately 80 Sq ft of lost floor space. So now you have to add about 100 Sq ft to compensate. That doesn't sound like much, but it is about an 8% increase in the overall size of the structure. 27% + 8% = 35%. That is rough math, but you can see that you are now much closer to the cost of exterior rigid foam. And, considering that you can use comparable or slightly cheaper, materials with exterior wall foam, it probably comes even closer. Additionally, if you live in an area where R40 is way overkill, the numbers probably are much closer. That is because rigid foam scales better with wall thickness than double stud constructions.

The info in this video is good and accurate. BUT anyone considering using this system should check out a "sip" system first. Better results with far less effort and as a bonus the longevity of sip systems doesn't rely on tape seams or later trades destroying the barriers. But thanks for the info.

Not sure that vapor barrier on the interior wall is such a good idea for hot/warm Southern areas, especially within, say 100 miles, of the Gulf. Our temp "delta" between interior & exterior in deep winter is only 45°F & only for few days. Unlike great lakes region or inland Mid-Atlantic "delta" of 70 °F for week on end.

How do you meet the horizontal fire blocking code R602.8 Item 1 with a blown in insulation?

The additiona materials and labor would take decades to break even, but if your client wants that fuzzy feeling go for it.. We like rich people spending money. Me, Ive learned about the point of diminishing returns so R30 walls are plenty, as long as it's air sealed well. It's the attic we need more fluffy stuff in and that's easy.