Chapter 14 of the 2018 International Residential Code addresses wall insulation requirements for exterior wood-framed, concrete, or masonry walls above grade, including cripple walls and rim joist areas. The code requires minimum standards for wall covering materials, such as material performance and fire resistance. Insulating walls helps prevent heat loss in winter, retain cool air in summer, and reduces noise. Kraft-faced fiberglass insulation is used in exterior walls to control temperature and humidity within the structure.
The code does not contain Electrical or Plumbing provisions and is effective from April 1, 2021. Construction, projections, openings, and penetrations of exterior walls of dwellings and accessory structures must comply with Table R302.1. Dense-pack insulation using fiberglass or cellulose is recommended for walls covered on both sides, such as sheetrock, plaster, or other materials. Foam plastic insulation used in exterior wall covering assemblies must comply with Chapter 26.
Foam insulation can be either blown-in/loose-fill or a blanket system, and it is suitable for all types of areas, from the attic to the exterior. The code requirement is R23 for walls in Oregon, and a vapor retarder shall be provided on the interior side of frame walls in accordance with Tables 1404.3 and 1404.3, or an approved design.
In summary, wall insulation requirements apply to all exterior walls of buildings, including cripple walls and rim joist areas, and require materials like foam plastic insulation, cellulose insulation, batts and rolls, loose fill, foam board, spray foam, and radiant barriers.
📹 Super Insulated Walls on a BUDGET?!? | Double Stud Walls Explained
If you’re building on a budget, but still looking to super insulate your home to maximize energy efficiency, double stud walls are …
Is R 19 insulation good for walls?
R19 insulation is commonly used in vertical walls framed by 2×6 studs, a common code requirement in some parts of the United States. It can also be used in floors and crawl spaces. To achieve R19 insulation, batts or blown-in methods are commonly used. Air sealing is crucial, especially on exterior walls, as leaky walls defeat the purpose of insulation. Insulating a wall with holes in R19 insulation is not recommended. An airtight, well-insulated home is a comfortable and efficient environment.
Is R13 insulation good for exterior walls?
The necessity for insulation in a given residence is contingent upon a number of factors, including the geographical location of the property and the specific architectural elements comprising the dwelling. Exterior walls typically necessitate insulation with an R-value of between 13 and 23, while ceilings and attic spaces require insulation with an R-value of between 30 and 49. In order to ascertain the recommended R-value and insulation level, it is advisable to utilise the JM insulation calculator in conjunction with the Department of Energy’s map.
What R rating for external walls?
The Building Code of Australia (BCA) sets minimum requirements for total R-values of buildings, which vary based on climate zone, building type, and heating or cooling unit usage. It’s crucial to determine your specific insulation requirements as different states and territories have their own exceptions. Higher R-values result in better thermal performance, and products with the same R-value have the same insulating abilities.
For external wall insulation, a minimum R-value of R2. 5 is recommended in Melbourne, Sydney, and Adelaide, and R2. 0 in Perth, Brisbane, and Northern NSW. Upgrading to a higher R-value can increase savings and thermal performance.
What is the R-value of insulation in Oregon?
In Portland, Oregon, the optimal R-value for attic insulation is between R-38 and R-60, while the optimal R-value for floor insulation is between R-25 and R-30. Nevertheless, in the event that the attic has already been insulated, the requisite R-value may be less than that indicated.
What insulation is recommended for exterior walls?
The U. S. Department of Energy recommends that exterior walls in colder climates have R-values of R-13 to R-23, while in milder climates, a lower R-value may suffice. Consistency in R-values throughout the wall assembly is crucial. Building codes, energy codes, and local codes should be consulted for specific requirements. Updated Building Codes call for continuous insulation on both below and above grade exterior walls. Insulation materials, such as type, thickness, and design, are used to increase R-values. Common insulation materials include:
What insulation is best for 2×4 exterior walls?
Batt insulation, which is typically the least expensive material, is typically used in 2×4 walls for R-13 or R-15 batts and in 2×6 walls for R-19 or R-21 products. However, for optimal performance, it requires careful installation.
Can I put R19 in a 2×4 wall?
The Department of Energy (DOE) Insulation Fact Sheet (DOE/CE-0180) provides information on the use of fiberglass and rock wool batts in insulation. It states that 2×4 walls are able to hold R-13 or R-15 batts, while 2×6 walls are able to have R-19 or R-21 products.
What is the best type of insulation for external walls?
Mineral Wool offers a unique blend of thermal, fire safety, and acoustic performance. Its breathable solution allows moisture to pass through the construction, reducing condensation risk. External wall insulation is typically finished with a render coat, and factors like thermal performance, finish choice, and fire classification are crucial. Rock Mineral Wool insulation offers both thermal and acoustic performance, making it non-combustible and suitable for both existing and new buildings.
What are the requirements for exterior wall insulation in Oregon?
The exterior walls are insulated with a U-value of 0. The conventional framing is 045/R-21, while the windows have U-0. The ceiling is flat and has a U-value of 0. 021. The framed floors have a U-value of 0. 017/R-60. Insulation of the slab edge should be of the F-0 variety, with a thermal resistance of 26/R-38. The number of items is limited to 48 or fewer.
What thickness of insulation for external walls?
Insulation systems (EWI) are typically installed using 100mm insulation boards, which can be impractical for certain areas. Thinner systems offer better U-value savings but are more expensive. Installation takes a few days depending on the property’s size, with most completed within 5-7 working days. EWI costs can range from £4, 000 for smaller terraced properties to £14, 000+ for larger detached homes, depending on the size of the house and the number of walls needed.
What thickness insulation for exterior walls?
R-19 insulation is a cost-effective and thermally resistant option for exterior walls, often used to meet building codes and energy efficiency standards. It is typically 6-1/4 inches thick and is suitable for colder climates or homes with high energy efficiency. R-21 insulation is slightly denser and 5-1/2 inches thick, offering better thermal resistance in the same wall cavity. Mineral wool is a strong contender for 2×6 walls due to its high density and fire-resistant properties. It is crucial to ensure insulation fits snugly between studs without compression, maintaining air pockets for thermal resistance.
📹 You’re Using Vapor Barriers Wrong | What You NEED To Know
The improper use of a vapor barrier can lead to more moisture problems, mold, and rot. In this video, we discuss how vapor …
You know what I would love to see you do? A similar article 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).
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
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.
Great article 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.
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.
I built my home in 1985 with 2 2x 4 walls 5″ apart, w/ staggered studs & 2 overlapping layers of 6″ fiberglass. Clad with 1×6 t&t pine over Tyvek, 6mil poly continuous envelope & 2×2 strapped for wire chase. The only issue I have had is the open nature of the stud arrangement is when a mouse gets in it can freely travel through the entire exterior wall cavity. Today I would build with a 2×4 wall with 3″ polyiso in between and 2″ over the interior strapped for wire and SR nailing
Amazing information and presentation. I subbed after your vid on vapor barriers being used incorrectly. Your website has an in credible amount of informative articles 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?
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.
I built custom homes until the mid 1990’s, I am now researching building a 1200 sf dwelling with about 30% of that as a garage. I’m amazed at the changes in the building technology. My design started with high ceilings with lofts and is now no vaulted ceilings. Thanks for the article. I can envision a world in the near future where all dwellings are modular and/or pre-fabled.
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.
Most of the pictures shown when he talks about “dense pack” cellulose are actually “damp spray” cellulose…water is sprayed on the cellulose as it is being sprayed into the wall cavity, which activates an adhesive in the cellulose that bonds it together. It is much less dense than a dry “dense pack” cellulose.
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 article 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.
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
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?
PLEASE HELP!!! I want to do 2×6 studs on a 2×12 treated base and double top plate. 24″ staggered studs… i want to simply double up 2×6 batts of fiberglass insulation in the cavity. use zip sheathing on the exterior wall and tape the seams. as far as weatherproofing, I think the zip 4×8 exterior coating would be enough if i used vertical furring strips and attached fiber cement boards directly to the furring strips. I plan on having at least a 2′ roof overhang. for the interior i simply would like to put up drywall. the assembly should be around 38-42 R im in central Kentucky (zone 4) i was feeling confident with my plan until you voiced your concerns for moisture… i dont think it is within my skillset or price range to install 3 separate vapor barriers correctly. and be perfectly confident there is no vapor that can work its way into the cavity. it gets pretty humid in Kentucky. basically what i need help with is if you or anyone else thinks fiberglass batts at ~r40 walls in zone 4 will have any moisture issues using zip sheathing as the only moisture barrier (unless you include rhe furring strips for an air gap as another moisture barrier) i will be doing a lot of the work myself. thats why it has to be done with my access to to materials and knowledge. this is my first house, i have the land now i need to plan the construction I can do the electrical, plumbing, and insulation, and some framing/ exterior (USMC aircraft electrician turn farmer) 😂
Having worked in construction, I must say what’s on paper vs what’s in real life are two very different scenarios. You want to have air membranes on the inside and outside of your double wall and the only way you guarantee the performance is if the membranes are more or less 100% sealed. I am yet to see any project in real life that lives up to that standard. Even if the carpenters get up to almost 100%, there will be other trades that will punch holes like nobody’s business or the home owner will make modifications/renovations, etc later on which will compromise your system. The moral of the story, the simpler, the better. If you must have a membrane, have only one and provide ventilation opportunities on both sides of that membrane for moisture to dry out. That’s a much safer bet in my opinion. So keep structure separate from insulation and keep insulation on the outside of the structure. My two cents
If the wall can dry both ways and the majority of moisture issues are generally from poor exterior practices even if some moisture gets into the wall it should still be able to dry if there’s proper dehumidification on the inside as well. The biggest struggle in there for me is a 1×3 doesn’t allow for use of regular electric boxes even lights and also venting so again more costs and labor. I really enjoy this article. Would appreciate you doing maybe a series and addressing some of the issues I’ve mentioned.
Amazing information and presentation. You helped me to understand a couple B.S. concepts i’ve been curious about for a while. I’ve been building with an emphasis on exterior permeability for a few years now. But what happens if you go to all the trouble to make the interior permeable, and then paint over it with a plastic (Acrylic latex) paint? It cuts off all permeability through the drywall, no? I personally like mineral-based paints, but that’s certainly not the standard. Thanks again!
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.
I got your solution. Instead of all this work/ layers/ chemical glued products and other very unhealthy building options. HEMPCRETE, a 3 layered breathing mold resistant super insulate wall. 12 or 18 inch hemp lime wall sandwiched between lime plaster on the in and outside. Seems to be so many points of failure with these systems. One leak and you might have a molding wall.
My house is 50 years old. I plan to change the outer wood panels next summer. I also like to improve the insulation with rockwool and better vapour retarders. Do you think I can put in new vapour retarders without removing the internal drywall(gypsum board)? Can I just put the vapour retarder at the cavities and tape it well on the studs? Thanks.
I always wonder about the details on how americans build homes. This was one of the most enlightening articles on this. I just dont get why massive buildings dont get build, full stone/concrete/”Autoclaved aerated concrete” or stimple full-wood. All those layers to navigate air and moisture add so many points of failure. Additionally you need an HVAC in the attic for an healthy room-climate. Let the home breathe.
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 2×10’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 2×4 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.
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.
Great article!!! Very informative. I wonder if you can do a similar article 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 article 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.
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.
I have an idea for a article 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.
So, my bone to pick with this article 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 40×40 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.
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
So, the Intello Plus acts to minimize vapor penetration to the interior of the wall, yet allows any vapors which may accumulate, to migrate from within the wall to the interior space. In the meantime the Blueskin VP100 prevents vapor penetration from the outside environment to the interior of the perimeter walls. Is this a correct understanding?
Blown in cellulose, wool, and other loose fill insulations settle over time meaning the top several feet of a wall may not have any insulation after a few years as it all settle downward compressing the insulation in the lower part of the wall lowering its R-value. Two ways to make a super efficient house ICF construction uses lots of highly insulative foam and the thermal mass of the 6 plus inch thick concrete core plus the fact that ICF homes are super air tight or just use 2×12’s and have spray foam installed in two 5.75″ thick applications a week or so apart so off gassing can occur after the first application.
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.
I really enjoyed your article on double wall assemblies. I believe this will be an excellent build in southern Florida. OH WAIT but we don’t have the cold weather. HOWEVER we do have the HEAT and some times a cold snap in the winter months. This being said I do not believe that we need that interior vapor barrier in Southern Florida. The worst constructed homes in the area I live of Northern Florida is very simply poor construction practices. The exterior brick, then 1/8″ foil sheet attached to the stud, 3 1/2″ stud wall then drywall or paneling. Now get this; aluminum single pane windows extremely poor construction I do not like fiberglass batts as insulation. Horrible to work with and over time it breaks down due to moisture issues. In Southern Florida I would like to build a 10″ double wall constructed wall. Use many of your principles of construction especially around the windows but use an 8 ply window construction as fixed windows. The only working windows will be the required egress windows in the bedrooms. All other windows will be fix panes with 8 ply about 3 1/2″ thickness and to protect them from hurricanes apply a 2″ clear poly panel on the exterior of the window opening. Install a good fresh air exchange system in the house and dehumidifier as well. Thank you for sharing your double wall assembly.
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 2×6 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!!!
True double stud walls are a pain to build and especially to trim. EVERY extension jamb,, and every door and window requires it, every part must be a custom width. I KNOW, I have had to do it, on several houses. What WORKS are truss studs. Built in a jig or fixture so every framing member is exact inside to outside. A couple dollars more? 15% premium. Passive solar, super insulated, works well in tandem. Doing one or the other increases cost without increasing performance.
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?
Why would you use blown paper pulp insulation when you could install rockwool batts? Do it properly the first time and you won’t have to worry about it – rockwool doesn’t settle, it doesn’t need toxic chemicals to stop it rotting or breeding insects, and it will be there insulating your home for the life of your home.
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.
Well, it’s only a 27% increase in material cost your framing labor for outside walls will double you’ll definitely have an increase in labor for the fairing strips plus all the added labor liquid applied membranes and all the custom door and window details. Yes you do get a very high R value, what you need to look at is what is the reduction in heat loss through the wall assemblies. Go find a point of diminishing returns with the energy savings will never outweigh material and labor costs. By the time you factor in all this specialty products and construction techniques, you would be better off building a conventional wall and adding spray foam.
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 article BTW showing multiple ways to achieve outcomes.
Great vid! 🤩 In sweden we usually don’t have a double wall with cavity, but we do often have a vapor barrier on the inside sandwhiched between the vertical wall studs and horizontal 2x2s that we nail the plasterboard to. This allows us to run the services behind the plasterboard but not piercing the vapor barrier. A good viz is youtube.com/watch?v=tJD8SPMfvV0&t=33s
To make an apples to apples comparison with external insulation, you need to include the cost of extending your foundation/slab/floor by at least 7.5″ to maintain your interior square footage. Then the double wall requires more labor so exterior insulation might be quite a bit less expensive than you calculate.
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.
Elaborate designs that rely on perfect details to keep them from rotting ignore the vast majority of construction practices, which is I want it done yesterday. The owner, the GC, and the subs all wanted the job completed yesterday, so workers cut corners. Generally, a worker is valued by how quickly they work. Maybe the elite top 10% of contractors charging top dollar can execute this system, which leaves 90% as eventual rot boxes. Its just not realistic for mass production.
all that glue and tape and plastic sheet is not going to age well. i wouldnt build a house that depended on 100% vapor barrier protection with no air infiltration. it’s an experimental idea with a track record of failure. you’re hmmin and hawin about the triple glazing. it’s not an option, it’s a necessity at r-60. recessing the windows also is madness. way too many points of failure when not flush with exterior. if you must use materials that can trap moisture and rot, shouldnt there be active ventilation? i want to see tubes in these walls that remove moisture actively. will little fans and temperature+humidity sensors. the other way to go is build with materials that don’t rot and which can breathe. an R-20 aircrete wall doesnt need an interior drywall surface or membrane. and can have a metal rainscreen on the exterior, no membrane. a lot less plastic, lot less points of failure. insulation, thermal mass, and structure in one.
Dense packed cellulose is R-3.6/”. At a PHIUS conference a few years ago there was a study done at 4 places across the country. They found that the interior RH in the thick walls stayed at 19% relative humidity year around. It didn’t dry out. You get mold at 21% RH. Good luck finding contractors that can put these details together.
I recently built a 14” double stud wall for a slab on grade house. The outside load bearing wall is 2X6, 2′ OC with 1/2” plywood. It is cantilivered 2” past the foundation and then the foundation is wraped in 2” of insulation that then has stucco applied to the exposed areas. Another practice I use is to not stagger the studs as it is not necessary with all the insulation in between. Crowned studs can be crowned opposing each other then tied in the centre with a narrow piece of plywood to straighten them out.
I love passive houses and the super insulation movement, but this seems like one too many fragile materials stacked on top of each other waiting for something to happen. A cellulose insulation that is protected from a vapor barrier that can get penetrated easily and accidentally when somebody hangs a picture. An insulation strategy that is too fragile to handle putting the shower against an exterior wall. I was hoping that our high performance homes wouldn’t be as fragile as a high performance race car.
Okay that’s a lot of Science. But, in the real world- #1) What about a future homeowner hanging pictures to the wall? Everything hinges on never penetrating the wall to prevent moisture & air. #2) What about a Future Kyle punching the drywall? Current home design centers around component repair of the house. Any piece being removed, changed, and replaced #3) what about future improvements or adaptation. When the Internet became popular, conduit was renovated to accommodate data wiring. #4) expansion and adaptation. adding electrical outlets to a room or Lighting fixtures. #5) Kids will be Kids. Who doesn’t know a kid that did something dumb and made a hole in the drywall. Bottom line- You’d almost need a triple wall just to meet that Ari/Moisture risk. A sacrificial interior wall cavity for any future homeowner needs. A home could sit there for +100 years. Your design would absolutely be derp’d by then by any number of owners or occupants during that time.
You are significantly increasing cost because we are adding footprint square footage as well as all the other items you mentioned (longer eves, etc.). Why cant people stop messing with long held and proven designs??? You are building future moisture problems which add even further lifespan costs. I’ve lived in one of these experiments from the 80s and literally almost died from the mold issues. My current house is in the far north and I absolutely never used these methods and have no underground spaces or wasted footprint. You need to build and live in your experiments then report back what you would have done differently. Put the money into your privacy and bring the outside in and stop worrying about making coolers with R60 walls!
So in the end, the reality is you are trying to create as close to a WINDOW type of nuetral atmosphere between walls. This is an over- engineered way to gain r-valuation that brings more than cost to the table. Most municiple inspectors are not that bright and a good 70+% have never swung a hammer or pulled a wire on a jobsite. Hence the reason they carry that 8″ thick book around in their car all the time. I have beena developer/contractor for 38 years, I am also an engineer (Mechanical) and whenever we introduce some new “PROCESS” we lose more money in wasted time proving the inspector and the planning dept. aren’t communicating with each other. Second problem here is th labor to essentially build out 2 exterior walls and to connect them. To say that the difference in cost of 2×6 studs to 2×4 Proves nothhing except that you can count pennies. Labor, engineering, time to get approvals, inspection delays because of detail clarifications etc. ALL COST MONEY. I am still amazed that with all the combined knowledge we have in the construction field today, we still can’t get around these facts. That a house…as supposedly poorly constructed in the 20’s or turn of the century continues to stand, doesn’t leak, has no mold and has lived through Quakes (west coast) hurrricanes, wind storms, snow and baking sun. I agree with codes and enforcement where people live in tight communities where set backs matter. I have long been a loud voice against rural code enforcement of Anything constucted with the exception of plaaces where sewer, water or storm drainage is connected to the residence.
R- Value is a poor way to measure insulation performance. It was designed by the companies to push their own products. And they used their power to influence the building codes to sell more of it. When the R-Value of Fiberglass is equal to an empty air cavity you can see the principals of thermal conductivity is more than just conduction. This old standard never considered radiant or convective heat loss and the testing methodology was designed to ignore them to continue pushing fiberglass products. I just finished rebuilding a 800 ft² home. I put 1 in polystyrene on all of the exterior walls and underneath the roof trusses and it takes 40% of the estimated BTU to cool this home compared to a regular 800 ft² home. This was tested without any drywall or insulation between studs.
Double Stud walls not so good idea causing sheathing rot. Building Science has several papers & studies on problems with double stud walls. The best option is 2×6 24 oc with exterior rigid foam panels for added insulation. The issue with double stud walls is that moisture from inside migrates & condenses on the exterior wall sheathing & never dries out. Over time the sheathing & wall studs rot. Exterior insulation keeps the sheathing warmer & prevents condensation.