WINDOW CONDENSATION The Learning Center No, condensation on windows is not the fault of the window. However, by replacing drafty windows and doors or installing a new roof or siding, you may reduce the air flow in your home, which actually causes your home to retain more humidity. To reduce condensation, humidity must be controlled and air movement must be generated. As the exterior temperature drops, the humidity level needs to decrease if condensation is to be controlled. New materials and techniques in weather-stripping, insulation, vapor barriers, etc., which are intended to keep out cold air, also lock moisture inside.  As a result, moisture created by bathrooms, kitchens, laundries, and occupants no longer flows to the outside unless mechanically ventilated. Generally, condensation on insulated glass windows is the result of excess humidity. Window glass provides a cold surface on which humidity can visibly condense.  The fog on your windows is a form of condensation - just like the water that forms on the outside of a glass of iced tea in the summer and on the bathroom mirrors and walls after a hot shower.  When warm, moist air comes into contact with the cooler glass surfaces, the moisture condenses.     2. Do windows cause condensation? < back to list of questions about window condensation 3245 Miracle Drive Murrysville, PA 15668 724-387-2991 PA Contractor ID PA001856