Windows can often get moisture or “sweating” by having excess humidity in the air. When the humidity makes contact with the cooler surface of the glass, the “sweating” occurs. This indicates excessive air humidity inside the room which should be reduced. Typical causes of excess humidity are: inadequate ventilation in the room, faulty central air humidifier, heavy drapes preventing circulation near windows. Additional exhaust fans are necessary to prevent “sweating” in washrooms and laundry rooms.