A.Contributing editor Paul Fisette responds: You have an interesting set of challenges, all related to your coastal climate's extended periods of high moisture and relative humidity. The mold inside the knee space indicates that the relative humidity there reaches 70 percent, the threshold above which mold and mildew will grow. In your case, I don't think ventilation is a good solution. In fact, venting could make the situation worse. The outside air contains a lot of moisture, so it's unlikely to dry out your damp interior spaces.

I think the smartest approach would be to redefine the thermal envelope by installing a continuous air barrier and insulation along the outermost boundary of the shell. With this strategy, everything inside the structural shell will stay close to the same temperature and relative humidity as your living space. I would advise filling the stud and...

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