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Is a WRB on both sides of the foam okay?

michaelbluejay | Posted in Green Building Techniques on

I’m re-assembling a wall to change the windows from innies to outies, and to add a rainscreen gap. To do this, I have to remove the 3/4″ polyiso foamboard in order to remove the windows (foamboard is on top of the flanges). The foamboard is glued to asphalt paper with foamboard adhesive, and probably won’t come off without damaging the foamboard. My plan is to reinstall the paper/foamboard combo to the sheathing, then put new housewrap over the foamboard, which will mean I have a WRB on both sides of the foamboard. I presume this is okay, but since it’s unusual, I felt I should check with the experts first. Thank you very much for your help.

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  1. GBA Editor
    Martin Holladay | | #1

    There will be no problem if you have asphalt felt behind the polyiso and new housewrap over the polyiso.

    I hope that your polyiso will be thick enough to keep your wall sheathing above the dew point during the winter, as explained in this article: Calculating the Minimum Thickness of Rigid Foam Sheathing.

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