We have a new construction home, less than one year old. Windows are the type that slide inward to clean, etc, vinyl, double pane. We have had temps drop below zero a few days in the past couple weeks. Whenever it gets below 0 degrees, we get condensation. Not the entire window, but along the bottom edge of the interior window, the space in between the bottom fixed window and the top slider, and in just a few windows it will frost in the bottom corner of the frame. Have checked humidty, and we run about 25%. Also have a call into the window rep, but haven’t heard back yet. Asked the window guy who installed, stated he used fiberglass insulation around the windows, which doesn’t make me particularly happy. The basement windows, however, are insulated with foam (trim not finished yet), and those also condensate the same way, so not sure if that’s it.
What other avenues would you explore?