Is Polyiso my only option?
user-484142
| Posted in General Questions on
I’ve got a 1924 home in Seattle, with 2×4 construction. On the exterior side of the 2×4’s, I have T&G sheathing and layer of felt/tar paper, and then cedar siding.
In the process of totally gutting it from the inside, and wondering about insulation options. From what I can tell, it appears that the only way to achieve code compliance is to cut/cobble 3.1″ polyiso into the stud bays. To clarify, I’m not interested in furring out the 2×4’s, giving up interior square footage, using spray foam, or taking off exterior siding.
Are there any other options, given constraints listed above?
much appreciated
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Replies
How bout a "cobble & flash"?
"Cobble" together polyiso board & then "flash" with spray foam?
Is the constraint your energy code? If so, nothing currently on the market has a higher R per inch than new polyiso other than some closed cell spray foams. Over time they will all end up somewhere around R-5.5/in but if you need R-6.5/in for code compliance, and don't want spray foam, I'd go with polyiso.
Are you sure you have to bring it all the way up to full code compliance? You might be grandfathered if you're renovating an existing structure and not touching the external siding. If you are stuck, then polyiso is probably your best option, just plan on a lot of time to do all the cutting and cobbling.
Bill
And search Craig's list and others for used polyiso. It can often be had for less than half the price of new. It's already offgassed all it's going to, so probably closer to R5.5/in, but you don't have to tell the code inspectors that.