Critique my Wall, thoughts welcome
sleaton
| Posted in General Questions on
So house is framed 16 on center 2×6, all windows have a porch over them 6′.
The OSB was just delivered, and we will be sheething the roof and walls this weekend.
So I can get 2″ polyiso cheaper than I can buy 1/2. I was thinking, the following.
1. have already sealed cracks and such with polyeurethane just cause I could
2. Sheeth the wall
3. Seal seams of OSB with polyeurethane, or a good tape (suggestions?)
2. 2″ of poly iso on outside of walls
3. 1×4’s for a rain screen on top of the poly.
4. Cemplank over that.
5. Inner cavity caulked.
6. Inner cavity filled with cellulose
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Sleaton,
You'll always get more responses if you tell people where you live.
I happen to know (from another Q&A thread) that you live in Austin, Texas -- but it would be helpful to GBA readers if you let them know your location when you post a new question.
Thanks Martin, yeah I forgot that. And thanks a ton for everyone's help. Just doing last minute scrambling when I realized the proposals from my insulation guys were all non compliant and did not make sense.
Also someone had mentioned that installing over 2" of rigid is a pain and would have to be perfect. Is it going to be a big problem, should I not do the rigid ?
Note to GBA readers: Sleaton has framed his house and received a delivery of OSB for roof and wall sheathing. Apparently the sheathing work will begin in a few days.
On this Q&A thread and on a similar thread that Sleaton started recently (Polyiso on both sides of sheathing?), Sleaton has told us that he doesn't yet know how he will insulate his roof and walls.
Needless to say, he's painted himself into a corner by now -- because there are many insulation options that Sleaton can't consider, because it's too late.
I'm sure that Sleaton will get lots of good advice from GBA readers, and that some solutions will be arrived at. But other GBA readers who are planning to build a house should avoid these hassles by finalizing their insulation plans much earlier in the design process. For more information, see Plan Ahead For Insulation.
Interesting commentary, I have noticed that on this site. People have a very specific view of how houses are built. Everybody apparently goes out, does months of research, then partakes off on building the perfect house, so be it. Some of us are in reality. Go out and hire a builder as most people do, and you will find that the majority of people are not doing half of what you preach, and the insulation contractors are even worse. So yes I find your comment insulting, I am going above and beyond reading everything I can find, doing everything I can to figureout how to do the best envelope possible within the budget. Now I know, I know, no body builds with a budget, they should all spend as much money as needed to again, do it right and perfect, which even half the people can't seem to agree on. Close out this thread, its not like I got help on it anyways, I got a he screwed himself commentary, well thanks, that will really help me in my decision making. I thought this was a place where you discussed green and energy efficient building practices whether it be a renovation, an upgrade, or something in progress. The world is imperfect, get over it, and see ya
Sleaton,
Honestly, I wish you the best. I'm ready to offer advice, and I apologize for the tone of my last comment. Frankly, it's frustrating for me to hear of so many owners who are halfway through a construction project when they decide to visit GBA to ask insulation advice. But my frustration is not your problem.
I think that it certainly makes sense to install 2 inches of polyiso on the exterior side of your wall sheathing. If you have to choose between caulking the seams of the OSB wall sheathing and taping the seams, I recommend tape. Either Siga Wigluv or 3M All Weather Flashing Tape are good choices for taping OSB.
If you do a good job taping the OSB, you won't need to caulk the OSB sheathing on the interior.
Best of luck with your insulating job. (One reason that it makes sense to decide about your insulating plan early is that it can affect your window rough opening sizes. In some cases, exterior rigid foam requires larger rough openings, to accommodate window bucks.)
Martin,
I understand your frustration. I share it. I am sure there are many different ways that users find there way here. Now mind you most people building don't have a lot of control unless they are doing all the building. I just had one builder tell me about how they charge 750 to change a light, imagine what they would want when you tell them to sandwich the roof system. I didn't even know I had a problem till I came here which I am thankful for. I was building a house, I paid extra for 2x6 construction thinking that is the best way I have know for years to get more insulation. I went to all the "experts" and they are just saying throw in bats or spray foam. Then they all tell you to under insulate and use open cell everywhere 5.5 in the roof, 3.5 in the walls, the codes are behind they explain. That is what landed me on this site, researching spray foam. It is probably even worse in our area as contractors don't have to be licensed here,
The site has been very useful, and while my situation is not ideal, thanks to so many good articles and comments on here I will finish my house and it will be better for it, even though I will have to compromise. I will still have one of the tightest houses, and I will figure out a compromise to do the best I can with the budget I have left.
Thanks for the 3M suggestion. I have seen Wigluv, and it looked good, not sure if I can get it, I am making calls now. But I am sure I can get 3M products with no problem. Thanks, off to make some calls.
Sleaton,
I'm glad to hear that you aren't giving up on GBA. Even though GBA editors and other visitors here are human -- and need, occasionally, to express our frustrations -- we really do want to help.
Best of luck.
So I can put 1/2 inch on the exterior. Same price as the 2 inch. But would still get the job done. It sounds like the 2 inch might really complicate things. If I do 2 inch, I will then put firs over it, and put hardi over the 1x4s. with 1/2 inch I guess a person could just put one of the wrinkly wraps or some type of thin screen and you could nail the hardi right to the studs.
Sleaton,
Depending on what type of window you plan to install, and whether you want innies or outies, you should be able to install 2 inches of exterior rigid foam without the need for a window buck. For more information on this issue, see Installing Windows In a Foam-Sheathed Wall.
ok I am locked in on my insulation dow 1/2 Unfaced Polystyrene Foam Board Insulation. Over my OSB. So I am looking to tape the OSB, having a hell of a time, if anyone has an idea where to get wigluv or the 3m tape in the Austin area, or prime, or something let me know. Then putting the half inch over that. Then I am double checking, the polystyrene is kind of a wrb. I was thinking of putting a stucco rap or some kind of commercial rain screen wrinkly house rap or whatever over the insulation. does that sound right ?
You can find 3m all weather flashing tape on Amazon. Its cheaper than wigluv. Tescon Vana is available at 475 supply. Its about the same cost as 3m.
Polyiso is awesome for a warmer climate like TX. 2 inches shouldnt be too bad as you can use standard screw lengths. Be sure to get 1.5" stud penetration. (Google CCHRC Remote)
"Innie" or "in-betweenie" windows work well with simple plywood window bucks. (I think there is an article at BCS however where Joe Lstiberek talks about how you dont need window bucks in exterior foam under 3 inches).
Any good housewrap will work if you are using strapping. Tyvek or typar would be fine. I would use it if the polyiso is unfaced.
best price online for 3M 8067 tape is R.S. Hughes. Significantly cheaper than either of the European tapes.
Sleaton,
Q. "I was thinking of putting a stucco wrap or some kind of commercial rainscreen wrinkly housewrap or whatever over the insulation. Does that sound right?"
A. Every wall needs a water-resistive barrier (WRB). It is a code requirement. Although it is possible to use rigid foam as a WRB, it's usually easier and more robust to install some type of housewrap as a WRB. For more information, see All About Water-Resistive Barriers.
Hmm after reading the article is OSB airtight, it has me wondering if I should be taping my 1/2 dow seams (the typical blue stuff) instead of the OSB. If OSB leaks that would put a major hole in my design, I don't have a blower door sitting around to test it with.
The foam should always be taped, even if it's not the primary air barrier. XPS foam (the blue stuff) typically shrinks a bit over a couple of decades, and even if that results in a gap in the insulation, if the seams are taped the hit in performance is limited, since it limits the convective flow rates through the gap.
OSB detailed as the primary air barrier should have better long term air tightness integrity than XPS- if you're reallly going to only tape one of the layers, tape the OSB.
Detailing XPS as an WRB with tape is also useful, even if there is a crinkle-wrap or other WRB in place.
Dana thanks just what I needed. I will zip tape my osb, not sure the best tape for the foam. Then probably commercial D over that, covered with cemplank
It's worth reviewing this, if considering using the foam as the WRB:
https://www.greenbuildingadvisor.com/blogs/dept/musings/using-rigid-foam-water-resistive-barrier
Two air barriers will outperform one. Perhaps others can discuss your chances of air-tightness without using a blower door (or similar).