Mold on inside of external OSB wall
Upon pulling a carpet in our newly-acquired home, I’ve noticed some mold under the window (1st pic).
After removing a piece of drywall I found what seems a big patch of mold on the inside of the exterior OSB wall. Interestingly, there is no mold on the fiberglass R-19 insulation.
There was no any vapor barrier or retarder behind the drywall and the house is in the climate zone 5.
What would be a proper course of action to proceed in this case?
Open drywall on the remaining exterior walls and put a foam / rock wool insulation in case this was cause by the vapor diffusion?
Do we need professionals to clean this up? The mold seems to be going behind the beams where it would be difficult to cleanup without removing the siding and the exterior walls which I would like to avoid.
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