Importance of Circulation

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