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Editor’s note: This post originally appeared under the headline “Breaking the Thermal Bridge With Tstuds” in Kiley Jacques’ Houses by Design blog over at Finehomebuilding.com. Considering all of the discussion this new product has generated here on GBA, we thought it was worth sharing Kiley’s post which offers a few more expert opinions.
“I believe in the idea of the thermally broken stud, as well as a future where the focus is on improving the performance of the first 6 in. of walls rather than simply making them thicker.”—Brad Stokes
Brian Iverson, inventor of the Tstud, has stirred the pot. His 2×6 and 2×8 Tstuds are garnering a lot of attention among builders, designers, and building science nerds of all stripes. Touted as a six-in-one solution to thermal bridging in wall assemblies, the thermally broken Tstud is said to be a cost-effective, energy-saving, eco-friendly framing stud for the ultimate high-performance building envelope. The company also claims the product is easy to work with, doesn’t require any special training, and is stronger than #2 2x6s and 2x8s. That’s saying a lot. Hence, all the chatter.
A few weeks ago, we discussed Tstuds on the FHB podcast (episode 186). In response to my comment about wanting to hear from someone in favor of the product, Brad Stokes, a longtime DIY home remodeler, did some research and gave the matter a good deal of thought. “I’m mostly interested in the idea of the Tstud,” he says. “Everyone seems to be advocating for thicker and thicker walls these days, as if space is free and there is no impact on interior room dimensions or encroachment on exterior boundaries. Most of us live on a fraction of an acre and have room sizes that can’t afford to lose several inches or more around the edges—not to mention the fuss and expense of all the jamb extensions.”
Brad made some additional points that I think are worth sharing—they are good fodder for builders and designers curious about the pros and cons of this product. I also spoke with Marc Sloot of SALA Architects. He has spec’d Tstuds for a project currently underway and was able to share first-hand experience. Both Brad and Marc have responded to concerns expressed by FHB senior editor Patrick McComb, which included: cost, R-value claims, fussy corner connections, thermal bridging at the bottom plate, stud width, the two-dowel breakage limit, the 4-in. nail-gun requirement, product availability, and general complexity of the build, especially in terms of running mechanicals and plumbing.
Brad begins with cost, saying: “The economy and availability of 2×6 framing is hard to beat, but it gets expensive in real dollars to add exterior foam or a secondary wall, and to extend jambs and rework the exterior details. And that doesn’t include the penalty for those of us working with a finite footprint, and who really need those extra 3 in. to make the countertop or a queen-size bed fit in the room. What’s a few thousand extra dollars on a six-figure project if you can get more comfort, lower energy bills, and make that countertop fit? At $1000 or even $5000 more, it’s an intriguing option to consider—especially since it’s probably much stronger than my only other option of building a 2×4 wall with foam. Whether it’s this product or something similar, I am a potential customer.”
Marc’s thoughts run along similar lines. For the project pictured here—his first to be constructed with Tstuds—he was after a wall assembly with a mid-30s R-value. He considered 2x4s with exterior insulation, 2x6s with exterior insulation, conventional framing with standard interior insulation, and the Tstud assembly. “The Tstud was cost-competitive for getting to that R-value,” he reports. “It was maybe even a little less when you factor in trips around the house applying different layers for other assemblies.”
Marc views the Tstud system as the middle ground between advanced building science and code compliance. “It’s the sweet spot,” he says, noting that the Tstud wall assembly is a standard 5-1/2 in. thick, yet it creates a high-performance envelope. Additionally, he appreciates the split-stud construction—sheathing as well as interior wall finishes can be applied straight to the framing members, which, he says, make Tstuds a good choice for heavy exterior siding such as stone veneer.
Having experimented with myriad high-performance wall assemblies, Marc is familiar with the challenges of window and door openings. “You regularly need to address thermal bridging there,” he says. “Even if you are adding continuous exterior insulation, there is at least one solid framing member at those openings. There are lots of ways to do it but you get into the weeds on the complexities of how to install and fasten the units, whereas the Tstud can go right up to the edge of the rough opening. That simplifies the process and uses conventional methods that framers are used to.” (Marc sees that familiarity as one of the biggest advantages of the system.)
As for corner connections being fussy, Marc disagrees, saying they are straightforward. “It’s just a single Tstud on the outside corner and a 2x nailer on the inside—like a California corner—for the drywall to attach. It’s advanced framing.”
Brad concedes one trouble spot and suggests a fix. “Framing issues like the long nails could be overcome if they offered a 1-1/2-in.-thick product for the plates. I would think the structural specs for these horizontal members would be more achievable in a 1-1/2-in. thickness.” Another option is to use conventional PT 2x6s for the top and bottom plates. Brad concedes a thermal-bridging penalty there but he feels it would still be an improvement over conventional framing. When asked about Tstud bottom plates, Marc admits he used a PT 2×6 for one section of the house that cantilevers over the edge of the concrete foundation for exterior insulation—in that location he was unable to use a Tstud plate.
With regard to broken dowels, Marc says instructions for a field fix are supplied but he has yet to see it be an issue. “My observation is that it is not hard to avoid the dowels. You can stick a screwdriver through the foam to locate them. From an electrical standpoint, there’s no reason to break any. If someone’s breaking dowels, they are going at it with aggressive tools that are unnecessary.” Plus, he adds, in colder climates such as his, the only mechanicals going into an exterior wall are electrical, which can be run through the foam without threat to the dowels. Brad seconds that point: “In Minnesota, we rarely put any plumbing in the exterior walls—except an occasional drain/waste/vent system. It doesn’t surprise me that Brian Iverson’s company is in Minnesota—this product seems like a good fit for our climate (zone 6). I found a local builder who has built 15 Tstud homes in the last couple years, and there is a new home that just broke ground nearby that is using Tstuds.” (He is referring to Marc’s project.)
Regarding the potentially cost-prohibitive nail guns, Marc notes that larger guns, such as this one sold by Stanley Bostitch, are in the $400 to $500 range—significantly less than the $900 cited on the podcast. “If many guns are being used at one time, then a larger-capacity compressor would be needed,” he notes, “but on my project, the framers are getting by with a standard compressor.” Brad adds: “If we can eliminate the specter of the 4-in. nail gun, maybe [more people] would warm up to the Tstud.”
Tstuds are pretty new to the market, so availability is going to be a question. For this project, Marc sourced from Titan Manufacturing, an Ontario-based plant making and distributing the Tstud across North America.
Of course, Patrick has company in his naysayers’ camp, including Brad’s son, who has a unique worry. “He’s a molecular biologist,” Brad explains. “He is particularly concerned about the chemical process of forming the polyiso insulation [that goes between the dowels for the thermal break]. He questions whether it is formed in a way that is healthy and safe when installed—especially since it is inside the exterior envelope.”
In conclusion, Marc says: “I asked the framers what they thought of the system. They said it’s a little different and they have to think about how they are putting it together, but it’s not any more difficult than stick framing. One thing they noted is the straightness of the material. They said Tstuds are consistently straight and stable. They aren’t seeing twisted studs like they do on conventional stick-frame jobs, where they typically return up to a quarter of the studs. So that’s a lot less waste.” Despite this being the framing crew’s first time using Tstuds, they are moving along as quickly as they would using traditional boards; and all of the tools used for cutting members to size are the same.
Just as I was wrapping up this post, I heard from design-build contractor Mike Maines. I had asked for his thoughts on the subject because he is a strong proponent of eco-friendly building products. He adds this measured commentary: “It’s an interesting concept and seems well-designed. They are using the least-bad closed-cell spray foam that maintains a high R-value. The thickness of the foam makes it a more effective method than more typical Bonfiglioli-type installations [the assembly Patrick favors]. On the downside, if any renovations are done in the future, unless this product gains broad market penetration, which is possible but unlikely, there is a decent chance that the system will be compromised due to lack of familiarity. Any system that requires multiple trades to change their habits is asking for trouble.” (Of course, this last point flies in the face of Marc’s argument, and it’s worth noting that Mike has not worked with Tstuds.)
Clearly, there’s something about the Tstud that warrants consideration. This video by Matt Risigner has elicited 2780 comments and counting. But will it take off? Like most forward-thinking products, it’s a wait-and-see situation.
If you have thoughts on the Tstud, please send them to [email protected].
Photos courtesy of Marc Sloot, except where noted.
For more on Tstud, try these links:
- BareNaked Tstud
- T-Stud Field Guide
- Modern Construction of Minnesota
- Pro User
- Green Building Advisor Peter Yost on the Tstud
- Technical Advisor John Shafer on the Tstud
- Green Building Advisor Readers on the Tstud
- 2019 Green Builder Media Product Pick
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22 Comments
Are there any concerns with this product being used in areas where earthquakes are a possibility?
Hi Calum.
In another thread about Tstuds, Peter Yost replied to this question. Here is his answer:
"In this TER for TStud (https://www.drjcertification.org/system/files/drj/ter/node/1567/ter1603-06tstud.pdf), it states:
"9.5 TstudTM is not currently permitted to be used in areas where the Seismic Design Category is D, E, or F"
But you should check with Brian Iverson at TStud because he has been working on getting approvals for hurricane- and earthquake-prone areas of the US."
"What’s a few thousand extra dollars"
Heard that one before!
“[Deleted]”
I'm on the fence with T-Studs, and hope they turn out to be as useful as they claim, but I find the "what's a few thousand extra dollars" comment a bit worrying too. What percentage of the framing material budget does that represent, and what's stopping us from using the same logic to spec. premium products for everything else? Hopefully what's stopping us is that it can add huge amounts to what are already inflated material costs that contribute to the current high cost of new housing
I wonder how much ccSPF waste is generated during the manufacturing process and how it is disposed?
To Brians comment #2:
Most of California is in Seismic Design Category D, E, or F.
...few thousand more ..... comment is AMAZING!
Some of the work we do is for people who havent held $1000- in their life!!! So, yes a few thousand matters
And still, there are loads of people building houses in high-rent neighborhoods on postage stamp lots where every square inch matters. And a few thousand $$ doesn't. T-studs might be a solution in these areas, but not in wide open spaces where space is cheap.
There are plenty of areas with expensive land that isn't in a seismic zone. Or a hurricane zone. Or......
Exactly!
“[Deleted]”
Having trouble putting this comment in the right place. From the Roosevelt Energy Technologies website: "The Tstud™ has been tested and passed for all Hurricane and Seismic Zones in North America, up to 16’ tall in exterior walls." But I don't see how holdowns can be installed on them. I guess long threaded rod and couplings will have to substitute. Anybody know how the cost of threaded rod and couplings compares to holdowns?
Charles,
That's a good point. None of the details our engineers here typically spec would work with T-Studs.
No doubt these add material costs.....but when all is said in done regarding materials + labor for a double stud wall or exterior insulation + a second nailable layer of sheathing, it would be interesting to see what the delta in costs really adds up to.
Absolutely. I haven't done the math, but other methods that break the thermal bridging come at significant cost as well. I would not be surprised to see labor + materials come in near equal or possibly less on a Tstud wall. It's a very easy assembly, fewer parts,
and they're light.
As the one who made the comment "What’s a few thousand extra dollars on a six-figure project ..." let me add some context. This is my project where we are adding a large two-story addition to our own home on a small city lot where we are already constrained by the setbacks on two sides, and are wrestling to find every additional inch we can for ADA accessibility and to make certain fixtures fit. Due to these constraints, I'm looking for the best performing wall assembly that can be achieved in a 6" wall. My choices are standard 2x6 construction with cavity fill insulation, 2x4 construction with cavity fill plus 2" exterior EPS, or Tstuds with cavity fill. I don't like the thermal bridging in a standard 2x6 wall here in Minnesota. 2x4 walls plus 2" EPS is interesting, but is considered non-standard even though it will thermally outperform the 2x6 wall. Tstuds with cavity fill insulation is a third compelling option. Since my space constraints are real, I can't simply add foam beyond the 6" wall, or afford to lose interior space to accommodate a Bonfiglioli wall or a Mooney wall. When your options are limited, "a few extra thousand" on a mid-six-figure project is a no brainer if it solves a difficult problem. I'm not splurging on luxury features and finishes in this project, I'm building a functional addition that needs to hit certain dimensions to work. If I lose even 2" all the way around, our floor-plan and design no longer works. So a few extra thousand is cheap if your design depends on it.
Brad,
You may well be right, but I don't think your description of the alternatives was quite fair. If the depth of the wall is critical (and I'm not sure that extra 2" usually is even on most tight lots) then the alternatives all start with 2"x4" framing. As it is allowed by code, was the standard until relatively recently, and uses the same techniques, what's the objection to it?
You then have four comparable alternatives: Exterior foam, Mooney walls, Zip-R, or Bonfiglioli strips - all taking up the same depth. T-studs may still come out on top, but the depth constraint isn't the deciding factor.
Malcom, I may very well build the 2x4 assembly + foam. I like it, and it is code ( at 16" OC). But I'm surprised at the pushback I'm getting on that option as well.
There are other differences between the wall assembly options that do matter to the city. Here's where it starts getting into the weeds. My existing house is non-conforming as it sits 4' from the property line where current setbacks are 8'. I want to strip the existing siding, add 2" of EPS, and reside with LP Smartside. If it were just the re-siding, the city might approve that, but the addition will extend one of those walls (and it's 2 extra inches of thickness) by 36'. A strict reading of code calls that "increasing the non-conformity" which could be denied outright or require a variance. This obstacle is common to any 6" wall system used for the addition. But there is a potential difference in the foundation placement. Pouring a new foundation that is 2" offset from the existing--which further infringes on the setback--may be a non-starter. But with a 2x4 wall, I could continue with the same foundation line as the existing and allow the 2" foam to overhang the foundation. This may be more palatable to the city.
Regardless, I'm evaluating all alternatives and my options may be limited by other factors outside my control. If I could use any of the systems, I would still be confined to 6" (due to interior dimension constraints) so I would then have to do a cost comparison of each along with the performance I would get for that cost. I think my comment about "what's a few thousand extra dollars" has been misconstrued as being cavalier about costs. To the contrary, I'm very budget conscious. I'm just trying to find a cost/performance balance that fits our situation. I only came to the defense of Tstuds because many in these forums and elsewhere have dismissed them as having no performance advantages or other redeeming qualities over other systems. Even though they may not end up being used on our project, I do think the idea has merit and I like the idea of using self-contained thermally broken framing components. Anyone building or remodeling in the city--on expensive lots--understands the pain of thick exterior wall systems.
Brad,
I sure didn't take your comments on cost a being cavalier. Spending extra on things that matter makes sense. What worries me is the general creep of costs on everything that has helped escalate construction prices so much recently.
And I do hope T-studs make a go of it, which may well bring prices down as they scale up.
The pushback you are getting on exterior foam is understandable. Unless the builders in your area are comfortable with it, I wouldn't consider it a viable option. You don't want to be the first adaptor in your area that helped them work out the bugs. Perhaps Zip-R might be a good alternative. It seems the closest to conventional construction - although we have had some discussion here around problems with installation centred on overdriving fasteners.
Actually, I'm not getting pushback on exterior foam--that's fairly common here. It's the 2x4 construction. As for Zip-R, I should look at that more closely and get costs, but I've read comments elsewhere that since polyiso R value drops at colder temps, it is not optimized for northern climates (we're zone 6). Here's one such discussion: https://www.greenbuildingadvisor.com/question/zip-r-sheathing-climate-zone-5
> I don't like the thermal bridging in a standard 2x6 wall here in Minnesota.
Generically, why? Ignoring rare space issues, if one can build a higher whole-wall R value for less $, why be concerned about thermal bridging?
I'm not sure what you mean by "ignoring space issues" as this is a huge factor for me. My question is: if you can't build a wall thicker than 6", and you can use any insulation material you want, what assembly would have a whole-wall R value higher than what can be attained with the Tstud? (I'm not shilling for them, I'm just doing research).
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