Double Walls
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- Опубліковано 19 жов 2024
- This video details a variation of double wall construction which has evolved in Fairbanks, Alaska to increase home energy efficiency.
In all three of Alaska’s climate zones, residential building codes mandate the use of a 6 mil polyethylene vapor retarder. Since this vapor retarder also serves as a home’s primary air barrier/pressure boundary, it should be installed as airtight as possible to prevent excessive air leakage and moisture movement into exterior wall and roof assemblies during Alaska’s extended heating seasons. In a generic double wall system, however, wiring and electrical outlets still penetrate the vapor retarder, and thus require additional air sealing measures to reduce air leakage through and around these penetrations. The double wall system described here utilizes an outer 2x6 wall and an inner 2x4 wall, with a continuous layer of 2” foam board separating the two walls. The vapor retarder is located behind the inner (2x4) wall and is located directly over the layer of 2” foam board, where it remains intact and protected.
The layer of foam board serves as backing for the vapor retarder and also provides a robust thermal break for the 2x6 exterior wall, elevating the r-value of the outer (cold-in-winter) side of the vapor retarder to a minimum of R-30. This allows the inner 2x4 wall on the inner (warm-in-winter) side to be fully insulated with fibrous insulations and remain safely above the dew point. Electrical outlets, ducting, plumbing, etc. can all be installed conventionally inside the 2x4 wall and remain protected from freezing. This insulation technique substantially increases thermal efficiency, bringing the total wall R-value over 40.
We welcome questions and discussion in the comments and you can also reach us at info@cchrc.org.
CCHRC website: www.cchrc.org
CCHRC UA-cam channel: @coldclimatehousing
Music: "Motivational inspiring music" by Alexander Blu from orangefreesoun.... The song is permitted for non-commercial use under license “Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)”
Double walls are real gold if you live by a freeway.
Built my house exterior walls exactly like this 14 years ago. Along with R60 in the ceiling I'm very happy with the cold weather performance. An added bonus is the walls are almost totally soundproof.
"Almost" soundproof, those double pane windows neglect even the best of soundproofing. Wonder if triple pane windows can truly be almost soundproof.
In the UK homeowners near airports get grants for treble-glazed windows.
@@norn7364 The technology is already there, triple pane windows are not the best solution, not in the conventional way at least. What you want is two laminated panes on the outer side and a single pane on the inner side, it's important the sides are asymmetrical. You also want more space than usual between the panes.
Downside of these windows are higher costs and also worse thermal insulation values, because the additional space between the panes allows gas convection between the panes.
@@norn7364 in my experience there does seems to be a big difference in sound transmissions between double and triple. I have triple on one side my house, very quiet, and double on the other side, and it's very loud. I will say however that the triples are bigger windows, so I think the surface area of the glass might play a part as well:)
We built a super insulated home based on the Saskatchewan house in Fine Homebuilding issue 11(?) back in 1984. It’s similar to this concept. That was two 2x4 walls separated to 1 foot wide by using 1’ wide strips of 3/4” plywood top and bottom. Visqueen was used at the time and placed as in this example behind the inner wall.
Without going into the rest of the construction details I can confirm that the energy efficiency has been excellent. The house is ALL electric, in Michigan, and 2500 sq ft with another 1500 in the basement. Until 5 years ago we never exceeded an average $175/mo for utilities (well, utility - no gas, propane, wood stove, etc.). Then we added solar panels and now we average about $30/mo. (The service fee is about $10 of that.)
In addition, our well pump died in the middle of one winter and took a week to fix. This put our ground water heat pump out of commission and we heated the house with 3 electric wall heaters that were only used when we were home and awake. Temp never dropped below 62 even though outside temps were in the teens to 20s at night. So, yes, this kind of insulation has proven very worthwhile over the last 40 years.
Moving to a mild climate fixed 99% of my insulation problems
Haha
Yeah, I suppose that's an option, too. But, with the climate changing as it has been, those "milder" climates are becoming *HOTTER* climates... and I run my air conditioners 5 months out of the year in zone 4 as it is. 🥵 Insulating provides energy savings whether it's keeping the house warmer or cooler.
No doubt eh! 😂
I run my ac year round.
Genius!! 🤣🤣🤣🤣
This is a wise decision when building anywhere.
Glad to see you mention keeping the vapor retarder above the dewpoint. If you haven’t already, a dedicated video on how to determine that is in order. 😉
The rule-of-thumb is vapour barrier 2/3 of the R-value away from the cold side.
@@k.c.sunshine1934 that works well in most cases, but in a climate where there’s 90F difference between indoor/outdoor temperatures any indoor RH above 33% risks condensation in the wall.
I would imagine there are lots of places like Alaska where the delta is higher than 90F for extended periods, which would require strict humidity control for the 2/3 rule to be effective.
Moving to 3/4 from 2/3 gets you to 45% indoor RH @ 90F delta, a much safer solution. You may need to play around with the construction materials a bit, like add some R value to the exterior side, but it would ensure a more robust assembly.
Thank you for pointing that out. That is one we can roll out this winter.
It wouldn't be code but would this work?
Install no vapour barrier, but after all the electrics etc are in and the drywall is finished, paint the interior with a robust vapour barrier, such as two coats of oil-based primer, or three coats of water-based stabilising solution. ?
@@DavidOfWhitehills I’m not an expert, but I have read the “airtight drywall” + vapor retarding paint approach is considered valid by many builders.
I’m not a fan of that method simply because I don’t believe it’s practical to detail the drywall to a level where I’d depend on it to keep moisture out of the walls, especially in a cold climate.
I’m in Canada, but not as cold as most of Alaska I’d imagine, and am nervous even with “smart” vapor retarders which still are much more moisture permeable than a poly vapor barrier.
I get that there are cases where the variable permeability would be an asset (where drying is desirable) like in cooling-dominant climates for example. But when you’re only cooling the house a few months of the year, or not at all, I’d personally rather keep as much moisture out of the walls as possible.
I used this exact system on my studio remodel 5 years ago and have been very satisfied with the performance.
We just had a pole barn built in northern Michigan. It has R7.5 foam board insulating all of the bents, then a 2x4 wall built inside of the barn walls, with an inch and a half off-set between them, allowing conventional R19 insulation to be installed. This created R26 walls and made running electrical wires quite easy, as shown in this video.
A well insulated, tight system is great. Adequately addressing indoor air quality and moisture levels on the inside are essential to completing this system. Recently inspected a very tight building with an HRV that had failed years prior and it was pretty destructive.
Yes absolutely. Sounds like you get it. Unfortunately its common for people to have an HRV in the home but maintenance and understanding of operation is lacking. Over the years here in Alaska I've seen failures in walls and roof systems of all types -and if those failures were primarily winter time condensation related, then there generally exists a high humidity component that plays a big part in the scale of the failure. We can have holes in walls and roofs. And we inherently have pressure differences across those holes due to the cold outside temps.......so if we throw in high indoor humidity levels AND those holes are in the positive pressure zone, then the moisture transport via indoor air leakage can be tremendous. When I go into a house with good quality triple pane windows - or even doubles in here in Fairbanks and there's excessive condensation on the glass I start looking hard at the ventilation component. Lots more to this obviously, but point is we have to have the indoor humidity control in AK in winter time.
Does no one offset the studs from the outer wall to inner wall anymore? That's how I learned to build double walls so insulation overlaps, rather than have insulation aps wherleaving insulation gaps where studs are.
Wall insulation and a air tight seal is still the best in my book and the wiring is way easier.
Better option is exterior rigid foam insulation which solves most of the condensation issues, cheaper & easier to install than double wall framing. I live in the south east US, & my walls are about R-33 with 2x6 24 oc framing & exterior foam insulation. I don't like to use vapor retarders as I believe it does not really work & leads to moisture build up. Joe Lstiburek (Building Science Corp) has several video presentations on the topic with double wall construction as well as moisture build up with vapor retarders. I recommend watching his "perfect Wall" presentations.
Vapor barriers don't really work well as they get full of holes for utilties (plumbing, electrical, HVAC) as well as drywall screws. The best option for air sealing is the ZIP system that is fully taped & nail holes caulked on the exterior side, and caulking on the inside of the stud bays as well as sealing any wall pentrations with caulk, or other sealing products. Even with the 2/4 wall for utilities, you can bet a contractor is going to rip a hole in the vapor barrier whiling doing his installation work.
Exactly.
This is very case dependent based on region, builder, etc. If you want to start a frenzy among piranhas, toss a salami in the water. If you want to start a frenzy among builders, have one builder stand up in front of a nation of his peers and say that he's got the best wall. Yes, I am very familiar with Joe's perfect wall and that building science has set a standard. Love it. Case in point, we have a variation of that wall here in AK called REMOTE wall. cchrc.org/media/REMOTE_Manual.pdf Uses all the principles as brought forth by Joe. Exterior insulation is a great approach, but has a comparatively steep learning curve and doesn't lend itself well to complex/custom structures with out a solid understanding of how every detail needs to be air sealed and adequately insulated. Think grade changes, decks, roof lines, intersecting exterior walls, bay windows, split levels, often limited residential budgets, etc. Keep in mind that my perspective has a spectrum that tries to include builders of all scales and skill levels. And as I wrote that manual over a decade ago, I have had plenty of time to see some of the challenges of the system (and builder feedback) on jobsites in zones 6,7, & 8 here in AK. And it continues to evolve. At this moment in time, this particular builder used the system in the video as he'd need 6" of exterior foam board (in two layers) here in Zone 8/Fairbanks. The foam board is currently as expensive as it has ever been. In addition, this home is two stories tall on a hillside so every exterior layer represents a trip around the building and more labor. Yes, I agree that with practice and planning much of the foam can be applied in advance before the walls are raised.......but not all of it and the attention to air sealing is critical. I hope that makes sense. These types of discussions have to have clearly defined common ground as there are so many considerations - otherwise the water starts to froth around the salami.
I have never understood why putting rigid foam on the exterior of a house is a good idea. Foam is a vapor retarder so water vapor can build up on the inside of the wall if you put a vapor barrier on the inside of the wall which is required by code in the northern parts of the country because there will always be leaks. Joe Lstiburek seems like a blow hard and the videos are boring.
Exterior insulation, with stringers, and either foam board or rock wool, and siding over top, allows you to inspect your structural framing anytime. If you do it right, it also breaths so the stringers don't rot. Also keeps things light weight. All that mass causes foundations to settle and is incredibly dangerous in an earthquake. It also allows you to check and refoam any air gaps from the interior, related to the framing and plywood. And if you have a wood stove, the metal on the stove and flu is the first condensing point in the room when it's not burning. So it pulls moisture from the air. And when it runs, the relative humidity is probably ultra low anyway.
Modern "construction" is basically a bunch of glue huffing meth heads who literally couldn't think their way out of a paper bag.
In northern Europe they've used cavity walls for more than a century, but using brick and block. The cavity used to be only air, but now they fill it with mineral fibre. The original purpose was to stop driving rain getting penetrating through the first skin and into the interior.
I like watching videos like this. Ruth and I live on the edge of the Western Desert of Western Australia where the temperatures are sort of +50C rather than your -50C. The problems are the same. Keep the home comfortable to live in without owning your private power station. Great video. Thank you. (I am stealing some of your clever ideas)
If it’s good enough to keep my coffee warm it’s good enough for my house.
Can you imagine having ceramic insulated walls?!?! That would be awesome!
Feller looks like a real builder. His left thumb has the tell-tale black nail from a framing hammer. 🙂
Good eye. I actually earned that removing an engine from a 75 Ford and being careless at just the wrong time. And yeah that little voice (as always) was there and I chose not to listen. So I got that thumb in trade. Ugliest thumb I ever had was when I was just starting off 35 years ago (pre impact drills) and had a #2 phillips bit cam out of a screw while installing flashing in the rain off a ladder. Had most of my upper body weight behind the drill and slammed that phillips bit direclty into the center of my left thumbnail as that thumb was holding the screw up. Had a wubba wubba thumb for a few nights and a thumb I couldn't take to parties for about 3 months.
The walls are great but what about those ginormous? Windows?
Why not double 2x4 instead separated by a 1" air gap? Cheaper and thermal bridge.
On 1984 I built my house exactly like this. Also, my inner division walls are double with inter woven sound proofing rock wool batts. My ceiling is R55 and my basement concrete wall is insulated outside and inside to a value of R35.
I live in Montréal.
QUESTION... does those large windows really kill all that insulation? I know windows don't insulate very much. should you build a home with less and smaller windows?
I'm not a builder, just considering building a lake home when I retire. Are the newer vapor barriers (Tyvek or others) better than the old black paper builders used to use?
Make the walls 16’ thick use all the window ledges as a bed n heat ur home with a candle 😂
My understanding was that the rigid foam is a vapor barrier providing that all seams/edges are taped properly. This all seems very redundant. Having done a similar construction on my pole barn shop if I could do it over I would have used more foam board or a few inches of closed cell spray foam and skipped the fiberglass bats.
Yes in theory. Caution in practice. I'd still lean on the poly over taping the foam board. The 6 mil polyethylene sheeting that Alaska's municipal codes mandate as the vapor retarder (and more importantly, the critical air barrier) is a sheet membrane that covers large areas and is sealed with a durable, flexible sealant (Tremco accoustical sealant typ.) at the overlaps and perimeter. We are now seeing 40 year old walls where that sealant is still going strong and tenacious as ever. The foam board represents a patchwork quilt of 4x8 sheets (or smaller) where every seam presents a potential vulnerability to air leakage. Foam board is more rigid, not always dimensionally stable, and the air seal is totally dependent on the long term adhesion of whatever tape was used to seal the joints to whatever brand and type foam board was used. In a production setting, this means the crew installing and taping all those foam panels has more opportunities to make mistakes that may go unnoticed. I also have to consider that for us in AK many homes are built on seasonally unstable soils and can experience envelope stresses, I'd say that while the foam-with-tape approach can work (and I've seen it work anecdotally in one-off cases where a conscientious builder did all the taping himself), for us the poly approach is the safer bet. Not arguing with you on the taping the seams issue - just giving you my perspective based on my experiences.
@@IlyaBenesch I see where you’re coming from. I just look at the cost of materials and labor these days and it makes me sick. I look at all these high end “UA-cam” homes and can only imagine what the final cost is.
@@IlyaBenesch Understood. Any concern if water were to find its way between the poly and foam board that it could get trapped?
How would the cost 40% more material and 200% more labor compare to the energy costs of a 2x6 home over 20 years?
And has the cost premium been reflected in the resale value of a double wall home versus a 2x6 home?
One point that wasn't mentioned is that the original 2x6 framing with insulation between the studs creates a cold bridge at every stud that reduces the overall thermal effectiveness of the wall. Although these cold bridges are still there in this construction they have been mitigated by the PU board insulation. However, greater benefit would have accrued had the PU board been on the outside of the 2x6 stud and then infilling with PU board between the studs with a vapour barrier over the surface of the internal face of the 2x6. The finish board can then be applied. This would obviate the need for an additional stud frame, saving money and space.
Im germany and Austria we use glued OSB on the interior as vapor barrier and wood fiber board on the outside. It is fail proof construction.
Additional cost is???
My home in northern New Hampshire was 2×10 on 16" centers... accomplished the same thing but in not near as cold a climate.
Ya....don't have those sort of problems down here in San Diego.
The fiberglass is open cell insulation, is the foam board open cell? It was my understanding a builder needed to use open cell with open cell or closed cell with closed cell to prevent condensation inside the wall.
Very interesting!
I’m curious if there are any disadvantages to this style build in a very warm climate like Texas. All I can see is higher initial cost but many life savings on the AC size and electric bills.
in a climate like that, where you dont worry about freezing or condesation and frost, go for a double wall or a heat shield that can vent well, like metal siding suspended a inch or two off the building open on top and bottom.
Good stuff..
2, 2x4 walls staggered with r-15 each and skip the foam and you have r-30. Electrician doesn't need to drill holes. Put vapor barrier on inside. Windows are what makes walls lose heat so concentrate on insulating ceiling.
The 6mil poly vapor retarder (mandated by municipal building codes in Alaska) serves as the critical air barrier. This means penetrations such as outlets need to be well sealed and unfortunately this almost never happens as it is difficult and time consuming to do. Given the air pressure differences between indoors and outdoors in zone 8, the aggressive air leakage (and associated moisture transport if the air leakage is in the positive pressure zone) is consequential. In addition, as constructed with the vapor retarder installed behind the inner wall, now plumbing and ducting can be run within that inner wall without freezing risk. Not so if the vapor retarder is installed on the warm side of the inner wall.
Could not see how the 2x4s are attached to the 2x6s ? Or maybe they are not, as to not penetrate vapour barrier? Love the system has it been around enough for a time/function test?
My guess is they don't need to connect the two walls, other than where they meet the windows and possibly at the corners. Looks like a pretty well thought out system to me. If it didn't work you'd find out pretty quickly in a place like Alaska.
This builder made sure the exterior walls were straight and then used long structural screws about every 2 -3 feet to tie the inner wall to the outer wall through the foam board. This had the added advantage of helping clamp the sealed overlap where the ceiling vapor retarder meets the wall vapor retarder. I have seen another builder not fasten the walls together but nail the inner wall to the trusses. Like all wall systems, this system continues to evolve in small but significant ways with different builders taking slightly different approaches in the details.
Does the fibreglass insulation not slump? Would it not be better to just use the foam insulation? Are these types of walls soundproof or can you hear everything going on outside? I’m in the Uk and we build houses with blocks and Kingspan insulation in the cavity. My roof has 150mm thick of Kingspan in it which keeps us warm in winter and cooler in summer.
Where does the moisture go that’s on the plastic?
Is my understanding correct that the outer 2x6 wall and the inner 2x4 wall are not connected?
DR HORTON LEFT THE CHAT
Nice
Why dont they double up on windows. There is plenty of room to fit another window with the existing windows. You can double the R value in the windows.
This would be absurd cost for little benefit. Triple pane windows (R7-8)are >40$ per sq ft. R21 insulation is 0.60$ per sq ft.
You'd better have good windows too.
What is your strategy for introducing fresh air into the home during winter?
HRV System. Dedicated combustion air for boiler and wood stove. Bath fans, dryer, and range hood ducted to the outside. Passive makeup air duct available to prevent excessive negative pressures when all ventilation appliances are running concurrently.
Way cool!!! I am a huge fan of insulation and thicker walls. Hard to find builders who know how to do it. I’m not willing to move to Alaska to find one however!!
How about building ICF construction?
V. Interesting, but what do you do about the great big holes otherwise known as windows?
I would guess insulated windows go toward the outer edge and you have a larger window sill capable of placing plants, etc to gather the sunlight.
@@briank3940 Tx.
A much easier and more effective systemis using mass timber for the external walls . this could be logs or laminated 2x stock to the desired thickness . CLT also works very nicely in this system .the insulation , usually wood fiber T& G insulation panels of similar thickness are used . existing log homes can also be easily retrofitted with the insulation panels . Moisture inside the house is controlled by the hygroscopic effect of mass timber . Both the walls and the insulation allows the house to ' breath ' .furring strips are installed over the top of the insulation panels to accept the siding of choice . this create an air channel between the strips that is open at the bottom and top of the walls allowing moisture to escape . i've lived ina house like this for about ten years and only have to fire my two ton soapstone oven every two days in winter .
Hello, great video! I have to put a tub/shower unit on an exterior corner in a cold climate (6B). From the outside in, I was thinking 2x6 exterior wall studs, cavities filled with Roxul Comfortbatt and then using 5/8" paperless drywall from floor to ceiling (sealed at the edges to the floor and ceiling). Then I want to build a second interior wall with 2x3's, a layer of Membrain and then cement board from floor to ceiling around the tub/shower enclosure (sealed at the edges to the floor and ceiling) Finally I would install the tub/shower within this second, interior wall (walls above the tub are tiled). Would you recommend any changes to this design? Thanks for your help!
Hmmm. I'm not sure why the drywall would be needed between the two walls? Otherwise as described I think it would work fine HOWEVER I highly suggest you share a drawing detail or a site discussion with an energy professional in your region for a second set of eyes directly on it. The bathroom is a high moisture/humidity area and exterior walls are involved, so getting a localized sense of the enclosure from a professional in your area may be worthwhile. That's me being duly cautious with advice like this. :).
Wow 2x6?
A guy in West Chicago Illinois built 6 or 8 houses like this 20 years ago.
Easier solution: You can use 2x4 construction with Zip-R12 sheathing and closed cell foam between studs. You get R-30 walls and it's water/air tight. No screwing around with building out window/door jambs as normal windows for 2x6 construction fit. You eliminate thermal bridging of studs. You gain more square feet by not using double walls. That's how we built our single story home last year here in zone 6a. It's the way to go. Why make things over complicated when air and water sealing is a huge part of a long lasting and well insulated envelope. Our blower door test was 75% less CFM than passing, even with a forgotten 6" open air supply duct to furnace room.
Note that 2x4 construction might not work for all homes without bracing or by code in certain areas. Huber has nailing pattern charts for Zip sheathing with high R-values that must be followed, along with rolling the Zip joint tape.
Can't have a vapour barrier on the inside when using ridid foam on the outside so that doesn't follow the 2/3 insulation on the outside of the vapour barrier rule-of-thumb so I'd be concerned about condensation in the walls.
@@approots Yep. No vapor barrier on the inside just using closed cell foam between studs with no exterior insulation too. But to your point, 2" of exterior isopoly insulation will keep the condensation point within the foam when using mineral wool between studs in zone 6 and an interior vapor barrier isn't recommended. Filling stud cavities with closed cell foam makes the wall cavity a continuous layer of foam to the outside sheathing with or without exterior foam insulation, so condensation can't form in the wall cavity. The 2/3 outside and 1/3 inside wall insulation rule doesn't apply for my described wall insulation method. It does for fiberglass and I believe mineral wool between studs as well.
@@bobbray9666 Thanks sorry I missed the closed cell foam part.
Nice wall system! What happens to the foam/vapour barrier at the top and bottom plates, or where the walls meet a roof or floor?
Typically the foam is installed tight to the subfloor. No sealant. At the bottom, the 6 mil poly vapor retarder is sealed to the subfloor with a 3/8” continuous bead of Tremco acoustical sealant. At the top it gets interesting. Different builders are trying different things. I have seen one builder who drove plastic capped nails through the 2” foam board and into the double top plate of the exterior wall at about 12” OC. He then used the plastic washers as fastening points for the staples that hold up the wall vapor retarder. The ceiling vapor retarder then laps and is sealed over the wall vapor retarder at the double top plate line. The 2x4 inner wall is fastened through the top plate, through the foam, and into the double top plate of the exterior wall with structural screws every 2’ - 3’ -which clamps the vapor retarder joint at this juncture. So that’s the best outside the box thinking on this I’ve seen so far. And all ideas on this are welcome. The traditional way to seal the ceiling vapor retarder to the wall vapor retarder would be to rip a 2” furring strip of framing lumber and fasten that to the double top plate. The wall vapor retarder would then be securely fastened to this strip at the intersection of exterior wall and truss. You do however, now have a small area of thermal bridging rather than continuous foam board all the way to the trusses. This area of solid wood would would be about R-11 for an 11” thick wood wall section. That is still double the r-value of the windows but purists may cringe at this strip of solid wood while others like myself might be conservative and use this approach while the system evolves at this point.
Overall double-wall thickness:
5.5" Outside fiberglass (R-19 or R-21)
2" Middle Foam board (R-3.5 or R-3.6)
3.5" Inside fibreglass (R-13 or R-15)
Total: 11" R-35.5 or R-39.6
2x6 SIP = R42+
All you need is plenty money.
isn't this the old Envelope Home concept?
Funny, this is also the only real way to beat the heat in Arizona.
Planning for a home to never flood is fantasy, those romax are run too low.
Great they are set back, nobody will be driving nails into the electrical wiring.
They need to be up off the flood zone, maybe?
Why not just use 2x12s as wall studs/framing lumber? Two applications of 5.75" of closed cell spray foam are sprayed in the bays, with a couple weeks in-between applications to allow curing/off gassing of the foam. This way you end up with an air tight, R-80.5 wall. There is no reason to make building in cold climates more complex than it needs to be.
While a fantastic sounding idea, that also sounds like the most expensive residential home wall design ever.
@@ProleDaddy It would be more certainly cost more to have such a heavily insulated wall, but having an R-80 wall means you can significantly size down both heating and if installed cooling equipment and there would be significant savings over the life of the home in heat fuel costs and electricity if air con is installed. I would rather pay more upfront and have a short payback period and then have minimal energy costs for the life of the home. Personally I would have a micohydro or solar system and again because of the high R value the hydro or solar system does not to be as large as a lesser insulated home saving money. I would also have a wood stove as a redundant heat source incase of a power loss or generator failure, but also because firewood is not traded on Wall St and can be cut and split off ones own property thus no government or corporate BS artificially inflating prices
The 2x12s would be a thermal bridge as well as being very expensive. You could get the same R value with a double 2x4 wall with a 4" gap in between and it would be cheaper!
But what's the r value of the windows? R4?
what are you proposing? No windows?
The windows only practically need to be good enough to avoid condensation. Keep them a reasonable size and it is what it is.
Agreed though; once you’re into an R40 wall your next step is better windows and doors, not more wall insulation.
Would this work in Zone 5 or 6?
I believe insulation works everywhere. Maybe your heating bill will be too low, though. ;)
I believe that it would work anywhere; insulation can keep heat in or out.
🤭 Of course, silly 😉
One reason we design walls differently for different climate zones is that we want to prevent moisture from rotting out our walls. A wall that works well in Miami may not work well in Chicago. There is a whole science to designing walls and complex computer programs to model the movement of moisture and vapor and the potential for condensation. How you layer the different parts of the wall (insulation, vapor barrier, sheathing, etc.) is important. How much insulation and where it is placed is also important. The wall design in this video is new to me and I don't know how well it would work in my climate zone.
You says the 6mil plastic to be installed in the warm side of the rigid insulation and your diagram shows it in the outside. Am I wrong or you guys are not as thorough as you should be. What about in the actual work site, do you guys make the same kind of mistakes.
Just build double 2 x 12 walls, and the R-value will meet code for the next 15 to 20 years😂 or better yet double 2 x 20 micro lambs for straighter walls.
Guys...move the foam board to the outside of the 2x6 wall then seal. Then fill the cavity. More bang for your buck when you don't let the air in.
There are a lot of critical caveats to this statement that would need to be clarified in order for it to work. Then you will have to consider the economics. This builder chose this system as he felt it more cost effective over using the 6" min of exterior insulation required in zone 8 for this approach to work safely.
Single wall SIP..
All homes should be made this way, but unfortunately they save money and you, the home owner have to spend more on heating costs. 😖👎
I don’t like the plastic vapor barrier. The slightest failure of cold getting to it from outside will cause condensation and mold potential. I haven’t seen a perfect insulation job ever. I will never recommend plastic in a wall.
That’s cute. Alaska is warmer than most of Canada.
I don’t know why we don’t use the Earth itself studying building everything above ground should I have at least one story below grade
Then you lose it all in the windows
Mold. Always mold.
R40 walls, great.........then you have R5 windows all over the place, really? .........all a lot of 😨B.S!
Smart building codes. These would be beneficial in every climate zone…. Would cut down the cost of air conditioning in southern hotbox zones as well.
👍🏠🇨🇦🪜🪚🔨
Why are there doubled up studs on the inside side of thw double wall, Isn't the inside wall just holding up the drywall?
You know, I hadn't noticed until you pointed it out. I can speculate that the 2x4 framing is comparatively cheap and the builder may have chosen to have his crew frame the building conventionally with king studs/trimmers around the exterior openings based on conditions in the moment. Sometimes things happen fast and the guys framing go with what they are familiar with. Or perhaps there's a wider window casing detail I'm not aware of. In any case, you are correct that the inner wall is not the structural wall and it could get by with single stud framing around the window openings as long as all aspects of the design are adequately backed and supported. I'd be cautious with doors since residential units tend to be inswing and need decent support on the hinge side.