Last month as I was doing an Inspection, the question around the reason for being called to do the inspection was moisture on the windows, primarily in the upper level of the home.

There are more than one reason for moisture to form on glass such as windows and doors, especially in the winter; this could be because of old style windows, single pane glass, another possibility is air leaks around the unit in question.

However in this home ( newer construction) only a few years old, with new efficient windows and no air leaks, the problem was becoming serious enough that the wood at the bottom of windows was showing signs of rot, 1/2 of the windows were on the east side & 1/2 were on the west sidesun on some in the morning & on others in the afternoon, this appeared to be happening both in summer as well as winter, there was air-conditioning for the heat & heat for the cold weather, but what the home lacked was air circulation.

Dead air space around windows & doors will most often cause moisture to collect on the surfaces, it was of course more noticeable on the glass, & because of the heating & cooling cycle of the sun on the windows. Remember that air movement is important both to heating as well as cooling cycles.