After 30 years of seeing jobs before and after, I saw something I’ve never seen before. An atrium full of vapor, the kind of cloud you might expect from a shower room or sauna, except hanging above a stairway in a sky lit atrium. The house didn’t feel cold but the humidity was so high outside that all the glass window and door panels were sweating outside.
I was originally asked in the store by the contractor for advice about a mildew problem. So we recommended a mold resistant paint. Turns out his mold problem was exacerbated by a tremendous moisture problem.
The moisture in the air was condensing on the walls and causing them to sweat. Surfactants leeched out of the fresh paint resulting in wet streaky rundowns on the wall and over the trim to the lower wall surfaces. The moisture also caused other problems including blistering.
The contractor had installed a 300 cfm fan mid wall but it was off for 12 hours a day allowing the moisture to accumulate.