Exterior GPS insulation with built in drainage on 90’s cape.
First time caller, long time listener here. I’m working on retrofitting my two story saltbox and had some questions about my wall assembly set up and if it passes muster.
2×4 walls with r13 batts with kraft facing.
1/2 inch Plywood Sheathing
Tyvek House Wrap.
1.5 Inches GPS Halfback at around R7 https://www.progressivefoam.com/product/halfbackh20/
Vinyl Siding or rain screen and LP smart side.
I believe the GPS is a great product by being both semi permeable and better r value than EPS. This particular product has a drainage plane built in at the expense of some r value. I’m in Maine so climate zone 6 so I’d like to have R 7.5 per IRC even if I do have a shoddy level 2 vapor barrier (kraft paper). Is R7 still fairly safe for this assembly? Thanks!
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Replies
You are close enough to the r7.5 that I would not worry about it. Your faced bats, even with shoddy install are still class II so the wall will work with even less anywas.
The grooved foam makes sense with EIFS, not sure if it buys you anything with regular siding. Nothing wrong with using it here but I would not spend too much extra on it.