Mold inside cavity wall
Hi Folks:
I hired a contractor to replace the siding of my house in NC (built 1985) and they should start next week. My residing plan includes adding 1/2 of polyiso over the sheeting (some plywood and some fiberboard) and then adding the fiber cement. Now, when I opened the wall from outside to run some conduits and to my surprise found mold on the plastic under the drywall. The mold is on the outside facing side of the plastic and also on the fiberglass insulation. The whole house seems to have been done like that: cavity filled with fiberglass with no vapor barrier, plastic and then the drywall.
So my question for the experts: what should I do. I see several options:
1- move ahead with the current plan: remove wood siding, add 1/2 polyiso over plywood/fiberboard and ignore the mold. I know I shouldn’t have the plastic there but my climate is 4A, so I wasn’t expecting any issue with mold.
2- Use this opportunity to remove sheeting, remove plastic and replace insulation that is contaminated with mold.
3- Replace the siding but don’t add insulation. Mold is not technically getting inside the house but on the exterior side of the plastic.
Let me add that I didn’t inspect all the walls in the house, only two places. A third place that I was able to check didn’t seem to have mold.
Thanks for any insights.
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Replies
Delete plastic. It is a cold condensing vapor impermeable surface. The AC sucks moisture inside, it hits the plastic at or below the dew point, and you get mold. Classic reason for mold in the south.
The pros will chime in soon on the most ideal solution; whether poly iso is worth it in your area or not and such. I think they will advocate for locating the air barrier on the sheathing exterior or taping the polyiso and leaving the rest of the wall vapor-open and adding a dehumidifier to your home. Good luck.