Is installing XPS Rigid Foam from inside wall safe from moisture problems?
zekers59
| Posted in Energy Efficiency and Durability on
I have 2×6 framed walls in my home. R-19 kraft faced. Outside sheathing is OSB that has Builders Felt with Metal Lathe attached and then Stucco. I am pulling down sheetrock on inside to seal air leaks with elastomeric caulk. Can I seal each “bay” with caulk and then press in 1″ XPS Rigid Foam for even tighter ?
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Climate area is Kansas City Area. Either way I will caulk all four corners of studs against the OSB to help air seal. But I'd like to add some rigid foam if it will not cause moisture issues.
Roy,
If you are pulling down your Sheetrock just to caulk the stud bays, you may be creating work for yourself. To reduce air leakage in an existing house, the usual method would be to use caulk to tighten up the drywall layer (without removing it).
Martin -
Thank you so much for responding!
It is a major undertaking for sure - but I've already got the sheetrock down. Lot's of air leaks I needed to get to in upper and lower plates of the wall. Headers over windows with lots of air leaks. So - much caulk will be used and it helps tremendously. I want to stop air leaks before it gets to the drywall.
Roy,
What type of insulation will you be using to fill your stud bays?
Martin -
I'm reading your BLOG about this subject as we speak!
I'm really in NORTHERN EDGE of Climate 4a. Your blog mentions that this climate zone doesn't get cold enough (long enough) to cause moisture issue. This must be why the OSB looks so clean from the inside. This is a big relief to me as I was worried about the OSB rot problem.
To answer your question. I was planning on XPS Formular 150 R 5 - 1". But, I will use whatever you suggest!
Roy,
Is that all? Or do you also plan to install fiberglass batts, cellulose, mineral wool, or spray foam?
It will be like your Flash and Batt scenario.
2x6 wall has currently R-19 Batts…..
I can use 1-2" of Rigid Foam to get R5-10 , then either:
Re-use R-19 Batts although they will be squished a bit OR
Install new R-13 kraft faced Batts if compression is bad.
What do you think?
Roy,
OK, that's what I thought. Your approach is called cut-and-cobble. (I'll be publishing a new blog on the topic on Friday.)
The bottom line is: you can do it; it works; but it's fussy work. Each piece of foam should be carefully sealed at the perimeter with caulk or canned spray foam. Most insulation contractors don't have the patience for this technique -- spray foam (flash-and-batt) is much faster -- but if you are a homeowner with lots of time on your hands, go for it.
HI Martin -
Hey, I'm a fussy guy! I can get this done in a few days so no problem.
So should I use 1 or 2" of XPS and what about re-using the r-19 Batt or using new r-13?
Thanks you!!
Roy,
In your climate zone, either 1-inch or 2-inch foam will work. If you compress the fiberglass batts, you'll get a slightly higher R-value per inch than if the batts were not compressed.
Thank you Martin! I believe this will really make the interior much more comfortable by stopping those leaks - and save on H/C too!
On last thought…..
I take it leaving the Kraft Paper on the Batt insulation is okay?
Roy,
Q. "I take it leaving the Kraft Paper on the Batt insulation is okay?"
A. Leave it on or take it off -- it's your choice. It makes no difference either way.