Exterior foam decision — IRC table 601.3.1 — and housewrap over foam
I am building an attached 3-car irregular shaped heated garage and trying to make it energy efficient but not break the bank. Some last minute roof changes during framing have made the attic area of garage usable space which will become a bedroom some day
I did a 4′ ICF foundation because I want to heat the slab (partially by solar panels someday) there is 5″ of high density EPS under the slab (craigslist bargain)
2×6 walls were necessary so the exterior walls would bear more on concrete rather than ICF foam.
I have planned all along to install 3/4″ poly iso or 1″ xps on sheathing exterior which I now realize is not thick enough for a 2×6 wall construction because of table 601.3.1 guidelines.
Siding is to be vinyl
interior walls dense pack cellulouse
I dont like polyiso because it does not breath due to the metal skin on the panels. I also do not like the idea of nailing the vinyl siding thru 1.5″ xps (R7.5 needed to keep sheathing warm). Nailing furring strips onto the foam to attach the siding is not very appealing to me either because it will start to reduce my overhang depths and get me closer to my building line marker lines (yes, the lot is that tight).
So..Question Is. If I use 1″ polyiso (R6.5) for a garage which will be heated to about 50-60 degrees in winter how at risk am I of sheathing rot?
Also, I plan to use house wrap over the foam….I do not find much information on this detail…to me it makes sense as windows/doors can be flashed normally. In this case I would leave the foam panels UN-taped so to promote drying (in case of some error/failure).
Thanks for any input. If you can point me to other posts that is fine. If I posted in the wrong area let me know.
If someone can soothe my nailing vinyl thru 1.5″ of foam concern that will probably answer a lot for me.
any info on the untaped seams will also help much.
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