Condensation of moisture on interior windows occurs naturally when interior air with sufficient moisture (humidity) comes into contact with a cold window surface. Air can only hold a limited amount of water vapour at any given temperature. As warm room air comes in contact with a cool window surface, the air cools and loses the ability to hold water. If the moisture in the air is high enough or if the surface of the glass is cool enough, the water in the air will deposit on the glass surface. This is called condensation. Condensation typically appears on windows before any other surface because windows usually have the least insulation value of anything on an exterior wall and react the quickest to changes in outdoor temperature. When outdoor temperatures drop, you can reduce condensation in your home by limiting the amount of moisture in the indoor air. The number of occupants in the home will raise the humidity in the home and routine activities such as cooking, showering and laundry add moisture to indoor air. Plants, fish tanks and humidifiers are also examples of common household items that contribute to indoor moisture. Why is my window covered in condensation? 34 ANHWP.COM • ALBERTA NEW HOME WARRANTY PROGRAM