CDX over polyiso
Hi, I’m replacing some old LP osb lap siding with Hardie plank. The substrate under the existing siding is foil faced polyiso over the studs. I propose to install 1/2″ cdx over the existing Polyiso so eliminate the siding sinking into the polyiso when nailin, and providing a better nailing surface. Are there any thoughts of trapping moisture between the polyiso and the cdx? I’ve seen a diagram on your website using this system but I don’t see any use of a vapor barrier. Please advise. The home is in the Pacific Northwest.
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