STOP Building Walls with 2x6 Studs - Use this technique instead!
How can you eliminate thermal bridges in your new construction home? And, how do you build your home to maximize energy efficiency, but keep costs low?
Axel Sorensen is back to show our preferred exterior wall system, where we achieve a complete thermal break around the entire exterior of the home, at a low cost per square foot, with materials that are available at every Lowe's and every other traditional construction stores.
It can seem expensive to build a new construction home in 2023, and there are misconceptions about the added cost to build a new construction net zero home as well. With simple building techniques, we can keep costs of building net zero low, while still achieving great energy performance!
When building our net zero homes, energy efficiency is paramount, and we'll see the results of this in our upcoming blower door test. However, we want to also balance the costs and are constantly weighing "How to save money when building a house while achieving the highest r value possible?"
This building system for our exterior wall construction is just two rows of 2x4 studs, instead of a single row of 2x6 studs, with dense packed cellulose insulation. This creates an easy to build construction assembly with affordable and easy to find construction materials.
This is a cost effective building technique that will help you build a more energy efficient home, and reduce heating and cooling costs, by eliminating a thermal bridge along the entire exterior of your home.
For more building science techniques and tips, home tours, and information on net zero homes, SUBSCRIBE to our KZhead channel!
#NetZero #customhome #buildingmaterials #buildingdesign
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!
How is the second story's load being transferred to the foundation? Do you need something different from normal traditional exterior foundation walls?
That double wall works excellent on selective interior walls as well for excellent "sound insulation". Home theater as an example.
Build incorrectly. Should be 24 on center staggered that way it illuminates all cold spots and works out to be 12 on center.
@@gomelteam there was 3" of space between the walls so your comments make no sense. Sometimes a 2x6 is used for the top/bottom plate then staggered 2x4 walls on each "side" of that. These are separate walls tho!
@@Scott-sm9nm Staggered stud on a common plate make more sense. I've also seen I-joists or truss studs used at certain intervals (such as every 4') to add strength
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.
In the video I saw the way the mesh was installed incorrectly. It should be pulled taught and stapled to both sides of the stud with staples every two inches. The cellulose then gets DENSE PACKED so it does not settle. A completed wall should be bulging with the packed insulation.
We remodeled an early 90’s home with this dense packed cellulose. It was absolutely packed top to bottom 30+ years later. Home was warm and quiet as be - the original home had the same dense packed cellulose used as a sound barrier in rooms that should be quiet. I.e. between the master bedroom and living room. Loved that home!
The house my grandfather built had blow in insulation and I could get it up to 90° with the fireplace 2400sf ranch style.
@@13squared2009 Sounds really great. However, if in a hurricane or tornado region, I'd rather consider one of the concrete wall systems now available for home construction as long as it is virtually wind pressure proof.
It does come down to how it was blown in place. I've opened walls after a couple years when it was put in place wet, and it didn't settle. It may not settle if dense packed dry. If it was loose I'm surprised it only dropped 12 inches, but maybe it was partially packed dense. It still wouldn't hurt to have a way to top it off after a few years, or to be able to check it. If you have vinyl siding it would be easy to check it from the outside.
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.
Compare to what? 2x6 plus 4+" exterior insulation? Rigid insulation is expensive. The long screws to install it are expensive. 3/4 sheathing just in case you miss the stud is expensive. Sealing window bucks is also expensive. Believe me anything comparable to the r value of double stud wall is going far more expensive and complicated.
@MurDocInc Had we had all that information and not just the cost of the" 2x6s" in your explanation in the video I probably would have agreed with you .
As a piece work batt insulator I love the idea of 3 R12 layers $$$
I was thinking the same thing. Labor cost and extension jambs weren't mentioned. I've seen this method and the reason it was used was because of noise suppression. When the studs aren't touching or one solid piece, sound vibration is greatly reduced especially with insulation. He never mentioned this
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.
Right! The finished interior dimension will be noticeably smaller so you will have to pour a non-standard footprint. And I think you will have to use at least an inch of closed cell foam (more expensive). Wouldn't framing with SIPs be better?
"there is no totally effective moisture and air barrier", this is why you must use a vapour open WRB (e.g., Solitex Mento 1000) and smart vapour control layer (e.g., INTELLO Plus) on the interior wall.
Nope. You're repeating an urban myth, which says that warm buildings have moisture problems. Read Fine Homebuilding and the Green Building Advisor for explanations as to why this is only a myth.
@@paulmaxwell8851 It's absolutely avoidable, but it's not an "Urban myth". You can easily get moisture problems in "tight" homes from spray foam and vapor barriers not done correctly. A quick search on KZhead and you'll find plenty of homeowners complaining of dripping walls. Don't call it a "Myth", call it something that is easily avoidable if done correctly.
It looks like it might be a condensation trap to me also. Especially with the particle board exterior sheeting. The commenter that talks about 'Urban Myths' needs to study dew points instead of some low level fluff ra ra bs.
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.
Didn't think of the windows but was sure the thick wall was going to have an effect somewhere. That could be dealt with by stepping down to 2x6 near the windows to have sort of a shadow box effect.
Deep window wells are great if you're a plant lover :)
@@hiris1903 I'm sure the cats love them as well.
@@adamcarter74 We moved from a place with nice big window sills to an older place with none. The cat still tries to get into the windows, when they are open he makes it work, when they are closed he just bounces off. He tries either way.
@@hiris1903 All kinds of neat traditional treatments: coffered casings, bi-fold shutters, side bookcases, seats, french doors,..
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.
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.
But you can also do exterior insulation that doesn't take up interior space. Two inches adds R-10 and it's a complete thermal break. Put the thickness on the outside where it isn't taking up space over your foundation and zoning codes limit the size of your foundation.
It's a little weirder than that. 2x4 studs are 16" OC, 2x6 studs are 24" OC. Looks like 16" OC was required. Can't tell if the inner wall can be classified as structural (supported by sill plate tied to footer). In some locations, if the inner wall is attached to a slab, it has to be able to "float" to allow for heaving/settling, or can't be attached to ceiling structure. Cool idea, but video is missing some engineering details.
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 was thinking that too. I think it would be a code violation here.
I was noticing that too. Balloon framing was eliminated in most building codes due to the lack of fire barrier. Would definitely be better with some type of barrier at the floor level.
Same here. I worked with an electrician on roughs, and we had to be sure to plug our little holes with packed insulation when we drilled through a fire-block to run Romex. These walls have no block at all: Like old balloon construction.
The dense packed cellulos is a fire block. It is treated with borates and noncombustable.
Sense pack or rockwholl qualifies
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.
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.
Exactly, was wondering if it was still allowed for US building codes.
The insulation should prevent fire from spreading, right?
@@EchoMeToo Roxsul maybe, pink ahhh yuck.
This is what my first thoughts were. I worked on a house like this. There were 2 problems we were addressing. 1 squirrels being able to go anywhere in the house inside the walls, floors and ceiling. The 2nd was an unexpected situation, the ladder went through the outer wall (west side of house), all the moisture built up, soaked up and rotted the plywood from the inside. Prevailing winds pushing the moisture to that side of the building being cause and effect.
You would be looking for a fire block not fire stop(both defined terms in the code). Insulation is a listed fire block, so as long as the cavity is completely filled it would be code compliant. The concern would be if the insulation settled or slipped in the 3” gap, which is unlikely with batts. Not sure how the cellulose settles though
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.
yep, gota have that fire break.
Make that cellulose really dry, so it will stop a fire from coming the outside world?
I've seen motel walls made with 2x6 headers/footers and staggered studs (to either side). That will be helpful for sound isolation, going down into the bass. (That's why they did it). I've also seen a front wall of an old house with 2 feet of space in it, and it traps highway sounds really effectively.
@@CoopAssemblycommercial is different, engineering’s stamp prints, and take the liability of things are outside of adopted code. They are still required to meet fire barrier requirements
Are there any studies on cellulose settling over 10 years, or more?
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.
You would be losing usable square footage, there's an increased fire risk from not having fire breaks, if you are in zone 4 or above you risk condensation without an exterior insulation thermal break, and overall it makes sense to stick with 2x6 or 2x8 and add the insulation on the outside. Like you have a three inch gap here between the double internal walls you are packing with cellulose (3.5R/inch) when you can use that on the outside with polyiso (6.5R/inch).
If your an old retired carpenter than chances are you never constructed anything like this.
I came into this video expecting something I’d really want to tear apart and dissect, but I really enjoyed this! Thanks very much!
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 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.
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
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?
Good questions. Nothing is made to fit this wall thickness.
@@OKOKOKOKOKOKOK-zn2fy for the windows, you can easily, if needed, use plywood to make sils before the windows or doors go in, it will also give you large lips on the inside and outside. I would even make the argument that having a chase wall like that is good for your duct work, since you give them adequate space and enough insulation around them as well
the insulation would be the fire block. Or use Rockwool if you need to
Correct. The cellulose IS the fireblock.@@A-Sidhu
We build plywood window bucks. Child's play. If you've ever built a log home or a straw bale home this is a very familiar technique.
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.
Probably shouldn't use a 2x4 exterior loadbearing wall in a quality house. Think about mechanical penetrations in a 2x4 wall. Exterior Rigid Foam will require extra skills and labour from the installers. However, exterior insulation is superior than a double wall system, especially if you use vapour-permeable rock wool insulation.
Ontario (Canada) building code it’s now required to have exterior rigid foam insulation for thermal bridging. 2x4 is structurally sound for framing.
@jamesready5 2x4 is structurally sound but a 2x6 is much better if you have any mechanical penetrations. The cost difference is not much either. Build higher quality always. 👌
@A-Sidhu depending on design and location size constraints, in very small houses inches count and the difference between 2×4 and 2×6 could feel like it is a much greater loss of interior space than the two inches actually measures.
@@A-Sidhu For sure. And in Ontario 2x6 is still required for code for the R value. You could use thinner if you could achieve the R value required by code, but I agree, once you stick an electrical box in a 2x4 wall you don’t have much insulation behind it. And if your using anything but spray foam in that situation you better have and insulation and vapour barrier contractor that cares otherwise you’ll probably have gaps and energy loss.
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).
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
Very interesting approach. Thanks for sharing with the community.
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...
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.
Ive been a builder my entire life, and I am very impressed by this level of care in design and build!
Maybe if you build ONE house a year...and have an unlimited budget....Please your being banboozled here but good...
It's not a technique for all enviroments, but many of the places I have built are so cold it would save you money to build like this. I often find 2x6's to cost more than two 2x4's anyway. @@davecruz9893
@@davecruz9893 So says the guy that doesn't think about life cycle costs of heating a building.
Is your house built this way? Didnt think so, go get another booster shot 😮@@kerrryschultz2904
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.
Excellent choice with a downspray on the sheet rock !
So your wall cavity and exterior is about an R30. And your frame with the polyiso is about R13. I use R 1 per inch of wood and polyiso is after gasing about R 7 per inch. Well done.
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.
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 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.
What about just doing a layer of rigid foam on the sheathing for a thermal break? Thanks for the vid
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.
Not really. Yes it will cost more, but not that much % wise. Estimate a house cost, then all for another for a 1ft bigger or smaller. Won't be that much overall.
I enjoyed your very informative video, and I am looking forward to the next one! Well done!
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
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!
👍
In the inner framing I would have liked to see the studs staggered away from the outside wall studs, yielding a higher overall R wall value. 10 inch overall minus 7 inch of wood with 3 inches of cellulose yields about R 16 at the studs. Based on R 3 per inch of cellulose. Stud off set gives 3 1/2 inches of wood plus 6 1/2 inches of cellulose. Yields about R 21. Wood has an R value of about R 1 per inch.
I built this design 35 yesrs ago with 12 invh heel height om the ranch we've living in. Works extremely well
What part of the country are you in? Would something like this wall system work in the Texas climate?
@@steveschultz300 Anytime you increase the potential R value, you reduce your heating or cooling load. In Texas were you predominately have a cooling load your vapor barrier needs to go to the side with the heat, which would be on the outside studs.A 11/2 inch layer of closed cell foam would make a very good vapor barrier. Your windows are the weakest link in the chain.
Triple pane windows,@@kerrryschultz2904
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.
We have some commercial buildings that use this method in noisy areas such as along train tracks and hiways. Excellent for sound.
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.
Agreed! T-studs plus zip-R seems like the much better solution to the problem he is trying to solve.
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.
You don't need to insulate the common walls. The sides of your house have heated houses on the other side of them. There's no reason to insulate your house from a heated neighbor's house. Just insulate the walls that are exposed to the outside air.
That doesn`t make sense, mechanical rough ins are done before insulation. It's harder to run and cut batts around mechanicals, cellulose will fill in those spaces way faster and easier. Also thick walls you want to keep vapor open cause they can trap moisture so you want any moisture to dry out, spray foam would trap moisture and possibly cause rot. Cellulose also manages moisture better than other insulations, it's fire proof and lot cheaper than rockwool.
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. ❤
And, If you do this (slightly modified/a lighter version) on interior walls you get soundproofing, too, so. Great info.
He didnt mention it, but plumbers love it too. 10" of space to hide a lot plumbing and less chance of nailing into pipes.
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.
I was curious, and I'm not sure about the math, but for a 2000 sq ft house with 6 inch studs it would be 90 sq ft of stud space and a 10 inch double stud base would be 150 sq ft of total stud space. So across the whole house space you're losing 60 sq ft. As a single room, that's like losing a bathroom, but spread across like 9 or 10 rooms, I don't think it would be too bad.
@@AbbreviatedReviews It’s not bad, but I think most people would want the extra bathroom option and without doing the cost analysis, I’m pretty sure they’d just put the extra footage into the foundation thinking what’s another few feet gonna cost. I’m thinking it will be a noticeable amount.
Or he could use exterior insulation with an r value of 5 per inch that doesn't take up foundation space like everyone else. 2x6 is R-19 and 2" exterior is another 10. Exterior foam probably stops air and water better than cellulose.
I don’t know if I want to loose so much interior space. Like to support your channel
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.
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?
This could easily be solved with a Polystyrene barrier at the top of the floors, but yes as they were described there would airflow allowed. However it would be very minor as fiberglass batt would still slow the airflow by 60-75%
This could easily be solved with a Polystyrene barrier at the top of the floors, but yes as they were described there would airflow allowed. However it would be very minor as fiberglass batt would still slow the airflow by 60-75%
Polystyrene is not an acceptable fire breaker. That would actually feed the fire.
Cellulose is fire proof.
@@MurDocInc "Cellulose is fire proof." Slight correction: Cellulose is *HIGHLY* flammable, but the ammonium sulfate and borate that it is treated with almost completely negates that.
Err that gap around the second floor might violate firebreak codes
Insulation is a fire block.
@@approotsno it isn't
@@andrewshedron425 yes it is. Only if there's an actual air gap would it break fire code. Also, try setting dense pack cellulose on fire😅
@@andrewshedron425 lol yes it is. Have a look at the building code or google or just think about it. When you restrict airflow through cavities you restrict fire.
This is a common technique for building sound proof walls in recording studios. Very effective!
Great video. Short and to the POINT!! Perfect!
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?
His second story joist have to line up with the download. But as just from an insulation perspective yes offset would be better
Joists don't have to line up with the studs, the double top plate carries that load to the wall stud assembly
on one section I only saw a single plate@@brucemccauley8887
Maybe use a 2*10 top and bottom plate and stagger the 2*4 studs from outside to inside.
The plates would be a no no...a thermal connection from outside to inside. The separation is the must in this method.
@@AZ-vt7dt2x10 is roughly R13 which is considered enough for thermal break in building science.
if 2 x 10 is touching outside sheathing....that's no good unless there is r-max/eps on outside of sheathing...that 2 x 10 will transfer cold right to backside sheetrock.@@MurDocInc
@@AZ-vt7dt There must be fire blocking. You will always have some thermal bridges. The windows are the worst part of a wall by far.
I did exactly that when I built my house in 1983. Even the inside walls that have 2 inch continuous rockwool as sound insulation.
We did this 25 years ago 12'' wall and got the wirsbo heat system which wasn't hardly in states yet
More lumber makes more waste and more lumber mean more labor to install. Interested to see a breakdown of all the costs.
I recently built a 2x4 double stud house with 8-10inches of cellulose in the walls and 35 inches in the ceiling with "Aeroseal" installed. The other building method we were looking at was 2x6 with spray foam. I think we ended saving about 12k$-20k$ depending which sprayfoam contractor we talked to. Though i did most of the work myself and didn't have to spend extra money on extra labor. One thing we definitely noticed is how silent the house is with the double wall
I use layers of 2x2 furring on the inside of a standard 2x4 wall. First layer on a 45. I use salvaged lumber I rip into 2x2's. I love all the waste on new build sites because that's my lumber store. It is of course more labor but I slow flip houses so I don't mind trading time for lower material cost. And of course there's no way all homes could be build using salvaged lumber because there wouldn't be enough. But I'm happy to exploit this niche.
The average cost (labor and materials) of building the second interior stud wall adds about 15% to the overall framing cost. This will always far exceed the cost of doubling the exterior insulation thickness.....AND it reduces the interior space by 8%. Not to mention the additional cost of window installations.
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.
Joseph Lstiburek perfect wall . building science corporation has your answer. If you ever build a new house do it his way. has a series of very informative videos but a bit dry and he has cheap books on how to build the best house for your area. This broken wall is one of the things he recommends. It is called a Mooney wall.
Doesn't this method violate the building code for fire blocking the wall cavity?
dependent on area you live.@@coreyfranco7060
we had the dense pack in the apartments we used to manage, very quiet neighbors, and cheap utilities.
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.
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?
It won't meet code here particularly in reference to Hurricane wind loading
Not sure why you're thinking there's anything different from a standard build. The outside 2x4, plates and OSB would all be standard structure. The wider plates and inner 2x4's wouldn't be structural. They're just there as drywall nailers. For example I flip 1940's houses and I remove drywall and screw 2x2's on 45 to the inside of original 2x4's studs and then vertical 2x2's. Same result as in the video, almost no wood thermal bridging. Furring isn't load bearing. However I only do single story houses so not sure if there's something I'm missing.
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
Would like to see/hear how your handling doors and windows in your technique (flashing and water proofing).
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?
Depending on your zone, latex paint will suffice Edit: I'm sure you know, but when you move down into a more air conditioned zone, that moisture barrier on the inside isn't the way to go because of cold interiors instead of Northern cold exteriors
This is a good consideration. A lot of folks want 2/3 of the total R-value on the exterior if exterior foam is used. In this case, that's simply not posisble. But also, not necessary either I reckon as an 8+" thick wall with no thermal bridging is pretty darn good anyway.
@@bradley3549If you are zone 4, or higher especially in the moist area than you will risk condensation on the inside of your sheathing during the colder month of the year. Exterior insulation keeps the sheathing warm above the dew point and prevents this from happening
@@williamwchuang I did a poor job explaining, but that's exactly what I'm talking about. There is a caveat you don't mention and that is that you need exterior insulation. If you have an R25 wall and only put R5 exterior foam, the inside of your sheathing will still drop below the dew point. And if that exterior insulation is vapor retarding foam, now you have a real problem. The thicker your wall, the more exterior insulation you need to prevent that. At beyond a certain point, adding more insulation to the exterior wall becomes impractical. That was the point I was trying to make.
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?
It looked to me like a double plate 2x4 wall is taking the second floor load.
Also, the inner 2x4 wall has no sheathing. What gives it any racking strength? I suppose there is no wind blowing against the inner wall. But wouldn't any shaking eventually try to collapse the parallelogram if there are no diagonals?
I saw this type of construction being used in North Dakota about 40 years ago. They get some very cold winters.
How did you get by the need for a firestop between floors, within the wall cavity?(update: sorry talked about below). Also, on the exterior wall, why not 24 on center since it is only holding up the exterior wall? Is there a need to add Zip R on exterior with the 10 inch interior wall? At R-40, mechanical ventilation will be required for moisture control, will that system be on video?
Two questions: Could you use 2x3s on the inside? How would this compare to a 2x6 wall sheathed with Zip-R?
Lookup matt risinger engineered studs with dowels between them.
The best R value to overall thickness is actually a system like the one you propose. Exterior foam has an r value of 5 while cavity insulation is 3-3.5. Adding 3 inches of exterior foam gives you 15 compared to 10.5 of internal cavity insulation. Cellulose and fiber class insulation also settle and clump due to moisture. While exterior foam doesn't have that problem. So it will probably be a better solution over the long term and by long-term I mean 10 years or more, maybe even 5 years
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.
That's what I do. I stagger interior and exterior 2x4 on 2x6 or 2x8 plates.
Pretty much the same thing but double stud will be easier it frame. Imagine floating half the studs when framing on the floor, you need jigs and/or 2 guys.
I learned about staggered studs in two rows of 2x4s back in 1980! IMO using Roxul batts and insulating the first row before building the second inside row would be the easiest way to insulate. I'm thinking the wiring would be easier to run, as it could go between the two walls of studs too (with stapling in place per code of course), so electicial costs might be reduced.
It's six of one and half a dozen of another. Our home is staggered-stud, but our big workshop is aligned-stud. On paper, there IS a benefit to staggered-stud so that's why we did it. It's not more difficult, just different. Either way, double-stud is the only way we build these days.
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.
The added cost is labor, which is transferred to the customer. It has also been tests that show that cellulose settles over time leaving the top of the wall without insulation. That being said this is a great technique in colder regions.
2x4 cost $3.5, 2x6 cost $5.5, so the double 2x4 wall would be $1.5 more per stud…
Not to mention additional labor costs…
Plus double the labor, construction is too expensive as it is!
This is construction for sound proofing a recording studio. A cheaper option for sound proofing with highly effective results is using a 2"x6" plate with staggered 2"x4"s 1foot on center. Insulation snaked in between horizontally so that each stud has a dead air space on both of its sides with no communication from wall to wall.
Is seems like it would be soundproof as well. I think your right about cost effectiveness. Twice the 2x4 doesn't really translate to cheaper cost in terms of price of one 2x6.... Although wiring would be easier!
You essentially have 2 walls on 2' centers sharing the same plate.
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.
i like that head-space ... good thinking
I like it. But still think It is good to have exterior insulation to reduce the chances of any condensation. Would you put a Vaport Barier on the inside of the house??
Thank you for this amazing video. My question is regarding the installation of the insulation. Are you insulating the walls seperatly or as one. it wasn't clear in this video as you were showing the netting and insulation being blown in. I really like this design concept and would like to apply it here in Idaho.
What happens when that blown in cellulose settles and now there's an air gap at the top?
Blown in cellulose is what builders use for other people's homes. It's a critter haven and like you said, it will settle over time. My best uneducated guess is within 3-5 years you will lose significant r value. Best practice is exterior insulation and closed cell/Rockwood batt on interior. If money is no object, just fill the cavity with spay foam and call it a day.
@@mikenotta7079There is a reason they call it dense pack. It is packed with enough density to avoid settling issue. If your walls have critters in it, there are other problems to address first.
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'm in HVAC design and sales in Washington state. Upgrading the insulation and making a home air tight can be a huge savings! I still think the weakest link is windows. Most custom homes have way too many windows that are far too large. The best windows are usually only about R5.
This system is used in Alaska but the studs are 24" OC and offset 12" inner and outer framework.
Wouldn't it be more cost effective and efficient to build without traditional eves and wrap the house in 4" if polyiso?
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.
As far as resale people are cheap they won’t pay anymore then a normal walled house.
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
That's why I use standard 2x4 and then layer 2x2 furring for the inside. First layer on diagonal for shear so no OSB or ply is needed. Furring can be cull and/or salvaged 2x's ripped to 2x2. I never understood why even 2x6's were used. Super easy to shim out the final vertical 2x2's to get a very plumb and flat wall. Future warping risk is greatly reduced in a 2x2 and virtually impossible in salvaged wood. No top or bottom plate is needed for the furring so 2x4 plates can be used.
Let's not forget the additional labor for building two houses instead of one.
@@timhallas4275 Only exterior walls is done that way so it's not actually 2 houses.
Nobody buys lumber from home depot to build homes, those are remodel sticks.
@@BOAH247I know that. I was talking about the exterior framing.
Wow! Someone who knows how to build! 4”EPS Floor insulation. Great video! Thoughts on double exterior windows? I see these in Fairbanks, Alaska.
I’m curious about the sole and top plates. Are they also doubled and there again what about the bearing surfaces like the foundation?
The second story system creates a fire chimney
No it doesn't.
Insulation is a fire block.
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.
Don’t need exterior insulation if you use a vapor barrier. Warm moist air would not reach the surface.
This is why a vapour barrier can't have leaks - which is almost impossible. But impermeable exterior insulation (foam board) is also a problem in wet regions like mine where water can become trapped in the wall assembly.
@@approots You either dry to the outside or to the inside. Cold and wet region dry to the outside predominantly. In this video, they can get away with a class 3 vapor barrier since the double wall provides continuous insulation.
@@phamlam3720 Yes my point being that a vapour barrier on both sides of the wall is a problem. In wet cool climates like mine, impermeable exterior foam is a no go. Since cool climates need the vapour barrier on the inside, to use exterior foam it would have to be the vapour barrier so it would have to be at least 2/3 of the insulation to avoid in-wall condensation.
@@phamlam3720 And you are correct but only if the vapour barrier has zero leaks which is almost impossible and that's what I think @firstdaddy was noting. The best solution is the addition of permeable exterior insulation (comfortboard) to prevent condensation on sheathing where the vapour barrier leaks. But cost and waterproofing around openings becomes an issue. In the south, exterior rigid foam all the way.
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…..
A 2x6 wall with Roxul and 2" polyiso continuous exterior insulation, and rain screen will probably last longer. Cellulose isn't great if there's any moisture and it settles.
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.
By using the 2 by 8 that limits you to a 7 1/2 inch cavity. Insulation is probably one of the cheapest long term investments depending on what you use to heat the home and where it is. In the prairies were -30 to -40 is common in winter the higher R value is a long term buffer on increasing heating costs.
What about just adding exterior insulation with the sheathing? Like Zip-R panels, or adding Poly-Iso or EPS panels then regular sheathing.
It's good idea in the south, in north where you need 10"+ of insulation. Adding 4-8" of exterior insulation becomes really expensive and more complicated with details like long screws & window bucks. Cellulose is also an 3rd of rigid insulation cost.
Zip is overrated, and polyiso loses R-value in the cold. But plywood sheathing + self-adhered membrane + semi-rigid mineral wool is a great way to build a wall.
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.
We started doing 2x6 walls in Lake Havasu AZ in the mid 70s. Electricity was expensive, and it's HOT there. I learned that there's no such thing as too much insulation.
@@samelioto476no doubt but exterior insulation doesn't take up interior space, has better r value per inch, and stops wind/water. You need longer fasteners, though.
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.
Great video I’m kind of confused though when it comes to the joist for the ceiling, how you did the thermal break. If the joists are tied to the inside wall 2x4 and not connecting to the outside to stop at thermal break all the way around the house how do you keep your outside walls from moving if nothing’s tied to them thanks.
LABOR LABOR LABOR - who cares what the stud costs. Let's see the window buck detail on this 10-inch wall.
Slap some plywood around the openings? The window/door bucks for exterior insulation are more difficult to install and waterproof I'd think.
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.
Continuous exterior insulation. That's outside space not on your foundation. That's an R value of 5 per inch minimum compared to 3-3.5 for cavity insulation.
A 2x4 with R-13 cavity insulation and two inches of exterior insulation with an r value of 5 gets you to R-23.
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.
How would this spacing affect fire rating of the wall? I see the fire blocks on the inner and outer walls but noting in the 3" void space to prevent fire travel! If a fire we're to spark within the wall there is nothing to stop it, side to side or up and down. 😮
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?
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
I'm sure he's never thought of it. Thank God you're here 😂😂😂😂 it's a pain in the ass to insulate outside. Or you gotta run the zip r which is easy but pricey. Either way, this works too
@@natemartinez4595Insofast is fairly cheap and a great exterior insulation system. Build smarter not harder!
Wnat about fire blocks? You need to block the cavitiy to prevent/slow fire movement on ourside walls. How do you get that and a full fire break?
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.
Did you get an engineer to stamp these plans?
new construction .. kind of had to
@@theyhateme8763 it’s not required in my state
This is interesting. At this time, I can't see that it is better. Yes, those thick walls may save some on heating expense, but how much more savings there will be. Most of your heat loss is through the ceiling and not the sidewalls. I'm not sure where you are located, but in the United States we have to abide by the 2012 energy act. Obviously the double studs will comply with the act, but I'm not seeing the financial benefit. Maybe if I think about it more, I will. I do appreciate you putting yourself out there.
How strong is this wall compared to 2x6 during a hurricane, tornado or earthquake? Thanks. 🙏
Zip Wall sheathing cuts down on all that extra framing and labor by providing the thermal break when installing the sheathing.