I am intrigued by this product. Has anyone used T-Studs thermally broken wood studs on a project?
This product seems to be more of a residential product but here in the Pacific Northwest we use a lot of wood for Low and Midrise projects. We do that because of cost (wood is cheaper than steel) and thermal performance.
Where is NFPA 285 test for anything greater than a story in height?
I’m assuming this would qualify as Type V construction and wouldn’t need NFPA 285 testing (reference 2015 IBC 2603.5 and note that Type V construction need not comply with 2603.5.5 “Vertical and lateral fire propagation”).
Yes, that exception might apply to some low and midrise projects, but confident there are many that would not make that classification, in which case this product would be verboten unless tested/passed in accordance with NFPA 285, as I understand the IBC requirements for use of foam plastic in exterior assemblies.
I don’t know of any reference to NFPA 285 in the International Residential Code.
The R value of 20 for 2 1/2" of foam insulation looks high to me.
I’d be nervous about the nail holding power of only 1/2" of wood on each side of the foam in a 2 x 4.
Isn’t the IRC for one and two family dwellings? I don’t think lowrise and midrise projects mentioned by OP would be governed by the IRC.
What Paul said
How much heat transfer actually occurs through wood studs? we use thermally broken metal parts regularly now, but I didn’t realize this was much of an issue with dry wood.
Does the residential code require continuous insulation the way the “commercial” code does? This would seem to meet that requirement, although I, too, am squeamish about the structural capability. What’s the chance of shear failure through this foam “web.”
Residential code does not require continuous insulation…yet. The studs are stronger than solid wood framing.
Anne -
To your point, here are some generic/relative thermal conductivity values. I would consider wood to be a very poor conductor while being a marginal insulator…if that makes any sense.
0.08 softwood
0.07 urethane thermal break
0.015 XPS insulation
0.6 glass
35 steel
10 stainless steel
92 alum. alloys
Wood studs have an R-value around 1.4 per inch, so a 2x4 would be R-4.9 and a 2x6 would be about 7.7.
Using a more realistic R=5.6 for the foam, a 2x4 T Stud would be R15.4 and a 2x6 would be R18.2.
Studs comprise a little over 10% of the wall area, so the overall difference isn’t as significant as the difference in values for just the studs.
According to this website: http://www.coloradoenergy.org/procorner/stuff/r-values.htm
2x4’s R-value = 4.38 (U-Value = 0.228)
2x6’s R-value = 6.88 (U-Value = 0.145)
T-Stud 2x6 R-value = 20 (U-Value = 0.05)
I am replacing my post from an hour or so ago, after realizing that the T-studs are only available as 2-1/2" x 5-1/2" studs, so the calculations had to be revised.
Just as an example, using the R-values and U-values from Paul Sweet’s post, I calculate the following area-weighted R-values:
2x6 nominal solid wood studs, 16" o.c. with R-20 batts between studs: R-17.21
2-1/2" x 5-1/2" T-studs, 16" o.c. with R-20 batts between studs: R-19.70
So there is a significant difference in overall thermal performance of the wall using the T-studs.
so for all the engineering and glue and foam I get a net increase of 2? how about we place 1 inch of plastic insulation continuously on the outside and get 5+ or even 1/2 inch and get 2.5 + no fancy studs needed..(yes I’d have to use clips)..too much fiddling around for too little benefit IMHO
Mr. Chavez’s view may change once the thermally-broken wood stud manufacturer pays avitru to include them in masterspec.
oh so cynical…the manufacturer can ask all they want but …not every product has an existing place in our TOC (and we don’t just run out and write new sections for fun). Not every product makes it into MasterSpec regardless of money… but you can believe whatever you want.
I would be curious to hear what a structural engineer has to say about this product. T-Studs’ video shows walls using only single top plates, 24 inch spacing and less wood to frame a window.
I know from personal experience that good stable and straight 2x material is getting harder to find. That is why we are seeing more and more engineered wood on projects starting with plywood back in the forties and now I-joists, LVL, PSL, glulam, and most recently CLT.
I would expect a structural engineer would insist on “real” studs for king studs, perhaps at corners or anywhere where they want an additional tie down hardware, not to mention at sills, headers and top plates. So you are not even talking about all of the framing.
Looking at their website, I would think that one of these is stronger that a conventional 2 b 6 stud. It is essentially a truss (really isn’t thermally broken) with what appears to be 2 x material held together with wood dowels. More “stuff” at the extreme fibers to resist bending and, I believe a wwider member. I would be interested in looking at this to resist lateral wind load.