I personally had my walls sweat after I sealed up my house. Some areas would sweat in the middle of Winter, when I opened the walls up I found that those areas were missing insulation.
The problem was that I sealed my house so well that the humidity was not able to escape. Even using a good bathroom exhaust fan didn't help because it wasn't able to pull in makeup air. My windows and some parts of my walls would be dripping with water in the morning after a cold night.
I fixed this by simply leaving two windows cracked opened at all times, this was enough to fix the humidity issue and allow to bathroom fan to remove the humid air after a shower and replace it with dryer air.
Since it's Summer, I assume you are having a different problem, unless you are located in the North Pole, which you might be since you didn't fill out your location.
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