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Moisture behind insulation

[email protected] | Posted in General Questions on

I notice moisture behind the insulation on the plywood in my basement. Any ideas what would cause this?

Thanks for any help


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  1. Dana1 | | #1

    Air leakage from the humid interior air into the cavity is the likely culprit here. If that was just a bunch of batts stuffed between the studs with no interior wallboard, it's DEFINITELY the culprit. (And that's what it looks like in the picture- there is no evidence of prior drywall apparent.)

    If it had reasonably air tight latex half-inch gypsum on the interior that probably wouldn't be the proximate cause of the mold, unless you are on the cold size of US climate zone 6 or colder, or unless you actively humidify the air to something over 40% RH @ 70F during the winter.

    Before re-installing the batts, caulk the framing to the OSB at every stud/header/plate, as well as between the doubled-up studs & top plates, etc, and give it at least a month to dry out. Then install the batts as perfectly as you can, tucking them into the edges & corners then lightly tugging them out for a compression fit for the drywall layer, and slap on at least layer of standard latex primer to bring the vapor redardency well under 10 perms.

    Depending on your actual climate zone, you may want do put something even less permeable than latex paint on the interior, but without knowing your location it's difficult to advise.

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