Stud to Sheathing Insulation (Thermal Bridge) Barrier

[ToolsRCool]

New build, anybody apply any type of insulating tape along the outside edge of their wall studs as a thermal break before installing sheathing or their next outer material layer? Thinking to put a strip of 1-1/2" wide butyl tape, or adhesive foam strip, or.........? Pretty much same as you would the foam "gasket" between a bottom wall plate and a concrete slab, but instead on exterior walls outer stud faces. Looks like the R value of OSB is pretty low, so on decently insulated stud cavities, I'd think this could only help to lessen cold transmission to the studs and eventually into the structure? Not expecting huge gains, but if I have the chance to make a little bit of difference before covering it up, why wouldn't I?

Walls will have wind bracing diagonally across studs to prevent racking, not being dependent upon sheathing to do so.

 

[larry4406]

On our new construction builds, we don’t do this.

2x6 walls, R21, 16” o/c, normal firestop/ air seal. Exterior sheathing 7/16” OSB, Tyvek WRB, Hardy siding.

I am noodling out a master bath addition at my house. I might go with the Zip R system sheathing to get the thermal break you are looking for.

 

[ToolsRCool]

Good point, didn't consider that. Zip-R seems to add a lot of cost and thickness. I'm sure it works, but I'm right at the limit of my side setback to the property line (24"), and I don't want to set the new walls in any further than I already plan to by switching from 2x4 to 2x6. Small'ish garage, 26'x24', so every inch counts. Good suggestion though, I'm still on the butyl / foam tape train though unless somebody can talk me out of it?

 

[billconner]

The sill is for air. I don't think something as thin as butyl tape or the sill seal foam will do much for conductive loss.

 

[loganb]

It can make a difference on metal studs or steel framing as it can warm up the surface enough to mitigate/prevent condensation. On wood studs for a thermal break it's not sufficient to do anything. If you want to reduce the thermal bridging, will need actual foam like ZipR or a separate layer of pink/blue foam board etc

 

[cleveivy]

The tape or foam strip could help, but it won’t do much on its own. For a bigger impact, you'd need something like foam board or Zip-R.

 

[jack stand]

There's a lot of information on YouTube about this, but I think the simplest thing is a continuous layer of 1" foam, probably taped with sheathing on top of it.
From there, there's a double wall (2×4) with offset 16" centers and that's a floor space eater.

 

[Hank11]

Zip R sheathing is probably the best way to get what you want for the thinnest wall. You can have near 100% air resistance and moisture resistance all in one. You’ll have a really tight building if you pay attention to details.

 

[mike93lx]

If I lived in Michigan, I would absolutely be prioritizing external insulation. It's well worth the 1-2" added to the wall assembly

 

[240sxguy]

I hadn't seen the zip R before, very nice!

 

[C-S-H]

Walls will have wind bracing diagonally across studs to prevent racking, not being dependent upon sheathing to do so.

Wood is already a good insulator compared to other building materials except for actual insulation. The tape won't do squat. If you want to improve the R-value of the assembly, exterior insulation is the way to go as said above. If you use vapor impermeable exterior insulation like extruded polystyrene, you will have vapor partitioned the wall assembly and you need to get the exterior R-value to interior R-value insulation ratio correct for your climate zone (5A) to prevent condensation. You can also install mineral wool board on the exterior in any amount, used with a vapor permeable building paper. I am a big fan of vapor permeable assemblies in rarely conditioned buildings like garages and cabins.

Your OSB is the shear wall. It takes forces from wind, earthquake, differential settlement, global stability, etc. Nail it correctly and directly to the studs. The Zip R is a good product, but only works in certain locations. The metal diagonal bracing won't take any lateral loads until the shear wall is destroyed, and then it has very low strength.

 

[pembol]

Good point, didn't consider that. Zip-R seems to add a lot of cost and thickness. I'm sure it works, but I'm right at the limit of my side setback to the property line (24"), and I don't want to set the new walls in any further than I already plan to by switching from 2x4 to 2x6. Small'ish garage, 26'x24', so every inch counts. Good suggestion though, I'm still on the butyl / foam tape train though unless somebody can talk me out of it?

If you are limited on wall thickness, then go with 2x4 studs and Zip-R - the combination will be better than 2x6 and sheathing at the same thickness.

Sill seal or butyl tape will achieve next to nothing. The thermal conductivity of butyl rubber is actually higher than soft wood, so adding it would decrease your thermal performance by thermally bonding the studs to the sheeting. The r-value of the foam sill seal is likely less than 0.5 depending on how much it is compressed - this adds almost nothing to the overall thermal performance of the assembly. Use the time you would spend on this paying more attention to your air sealing details and the pay off will be better.

 

[ToolsRCool]

Appreciate the input from all, some interesting points I was hoping to collect. I'll re-run the numbers for 2x4 plus Zip-R, as the 2x6 was just to gain stud cavity thickness for thicker Pink Panther (R-21). I can make the walls as thick as whatever, just at the expense of floorspace as the new rebuild will be upon the existing slab. Slab is not insulated in any form, so fighting that anyway. Good points on air intrusion paths and being vigilant against such, I intend to do exactly that on the rebuild.

I also hope to make an overall cost per R graph, then pick where it makes sense to stop chasing diminishing returns. Identify what are the lowest cost things that have the largest impact, etc.....

The current structure is 40 year old wood T1-11 sided that is decaying and flaking away, open gaps and holes, zero insulation, 18' wide plain steel sectional door that is pulled away at the top, and a full open ridge vent. I run a combined 180,000 BTU's of heat as on-demand when working out there in the cold. It was never intended to be a winter workshop when it was built, and I am now using it as such. In comparison, should be able to heat the new place with a candle. Will be dead quiet as well, I'm stoked.

 

[duneslider]

Honestly, if this is a shop that you aren't going to be heating 24/7 like a house I would not go to the expense of Zip R. The biggest gain you will have is preventing air changes. Put zip sheathing on and do a good job taping all the seams and seal any penetrations. Get good door seals. Do 2x6 walls (you could even jump to 24" centers if you wanted) and do dense pack cellulose in the walls. That will be your best bang for the buck in this situation. If you wanted to improve that even more and get an R30 wall you could do the Bonfig wall method, its a bit labor intensive and will add a little more depth to the wall but you will end up with a great assembly that is pretty darn cost effective. Frankly, if your air sealing is done super good you could get away with batt insulation and save a few dollars over the dense pack and be just fine and be able to do all the work yourself. The key is really the air sealing no matter what you do. If the hot air can escape, the insulation doesn't matter. Just like your Yeti cooler, if you don't close the lid it won't work very well.

 

[pembol]

Appreciate the input from all, some interesting points I was hoping to collect. I'll re-run the numbers for 2x4 plus Zip-R, as the 2x6 was just to gain stud cavity thickness for thicker Pink Panther (R-21). I can make the walls as thick as whatever, just at the expense of floorspace as the new rebuild will be upon the existing slab. Slab is not insulated in any form, so fighting that anyway. Good points on air intrusion paths and being vigilant against such, I intend to do exactly that on the rebuild.

I also hope to make an overall cost per R graph, then pick where it makes sense to stop chasing diminishing returns. Identify what are the lowest cost things that have the largest impact, etc.....

The current structure is 40 year old wood T1-11 sided that is decaying and flaking away, open gaps and holes, zero insulation, 18' wide plain steel sectional door that is pulled away at the top, and a full open ridge vent. I run a combined 180,000 BTU's of heat as on-demand when working out there in the cold. It was never intended to be a winter workshop when it was built, and I am now using it as such. In comparison, should be able to heat the new place with a candle. Will be dead quiet as well, I'm stoked.

The r-value per inch is about 3.5 for fiberglass and 5 for the foam on Zip-R, so you will gain both by having continuous insulation over the studs as well as increased insulation between the studs. It is not cheap, but it does lead to a more comfortable and higher quality structure.

 

[billconner]

The metal diagonal bracing won't take any lateral loads until the shear wall is destroyed, and then it has very low strength.

Do you feel the same way about let in 1x4s?

 

[duneslider]

Do you feel the same way about let in 1x4s?

What's the point if you have sheathing on the exterior. It is just extra work that isn't doing any more than properly nailed sheathing.

 

[jack stand]

I don't see the value of the zip. If you put the same tapeing effort and care into typar or tyvek house wrap installation, especially for a workshop you can put those savings to where it will make a bigger difference than the zip or wrap.

 

[mike93lx]

I don't see the value of the zip. If you put the same tapeing effort and care into typar or tyvek house wrap installation, especially for a workshop you can put those savings to where it will make a bigger difference than the zip or wrap.

House wrap is a pain in the *** to install, especially on a tall building. If you don't care about that and aren't paying for the labor then yes, you can save some money.

 

[ToolsRCool]

More good stuff from all, thanks. Yes, self designed and constructed, so not paying labor for any of it, project is material cost only. Yep, 10' tall side walls and 22' gable peaks, but I do have a 30' 4x4 scissor lift to hang the Tyvek with. Will have every inch covered, and use their tape full length of every seam. Agree on the Zip-R cost adder as well, likely going to skip it and do other things like an R-18 sectional door and make the ridge vent closable, etc.... Likely just going 2x6 walls w/R-21 batts, Tyvek, R-38 batts in the rafter cavities, and have the place so air tight that any fart will stink for hours.

I only mentioned the steel wind bracing in case somebody was going to jump up and fight that Zip-R does not have shear rating. I'll still likely do the wind bracing just to appease the inspector and hopefully repeat a second visit, and honestly, I have no idea if any of the foam sheathed panels are shear rated. Would initially think not, but have not checked, and probably not going to.

 

[C-S-H]

Do you feel the same way about let in 1x4s?

Yes, weak and not stiff compared to the shear wall. And damages the studs at installation. A garage will have thousands to tens of thousands of pounds of lateral force from wind or earthquake that has to be taken to the ground. It takes hundreds of nails to do it, not just a few in a metal brace or 1x4.

ToolsRCool, it doesn't sound like you are open to changing your plans at all.

 

[loganb]

I only mentioned the steel wind bracing in case somebody was going to jump up and fight that Zip-R does not have shear rating. I'll still likely do the wind bracing just to appease the inspector and hopefully repeat a second visit, and honestly, I have no idea if any of the foam sheathed panels are shear rated. Would initially think not, but have not checked, and probably not going to.

The Zip R does have a shear rating on them per the linked report when properly installed

https://www.huberwood.com/uploads/documents/technical/Code-Recognition-for-Insulated-ZIP-System-R-sheathing-ESR-3373.pdf

 

[billconner]

What's the point if you have sheathing on the exterior. It is just extra work that isn't doing any more than properly nailed sheathing.

With just foam on exterior, drywall interior.

 

[CraigStu]

How about insulated vinyl siding?

 

[billconner]

How about insulated vinyl siding?

I've wondered about this, but isn't R value in the 1/4 to 1/2 range? certainly not like an inch or 2 of foam.

 

[CraigStu]

Yes, I don't expect the R is much. But the thread started off wondering about putting tape on the outside edge of a stud.

 

[billconner]

Yes, I don't expect the R is much. But the thread started off wondering about putting tape on the outside edge of a stud.

Good point. But as is typical of thread drift I was thinking about another project. I wonder if insulated vs uninsulated vinyl would be a noticeable difference. I know 1" of foam would be.

 

[ToolsRCool]

Yes, weak and not stiff compared to the shear wall. And damages the studs at installation. A garage will have thousands to tens of thousands of pounds of lateral force from wind or earthquake that has to be taken to the ground. It takes hundreds of nails to do it, not just a few in a metal brace or 1x4.

ToolsRCool, it doesn't sound like you are open to changing your plans at all.

You're mostly correct. I think I'm pretty fixed on what I am doing for the walls and rafters. Was just trying to check some opinions on the outer stud face insulation thermal-break idea.

 

[Dragfluid]

You're mostly correct. I think I'm pretty fixed on what I am doing for the walls and rafters. Was just trying to check some opinions on the outer stud face insulation thermal-break idea.

Did you see at all, the things that I wrote?