What is exterior condensation?
Exterior condensation is moisture that forms on the exterior glass surface. Condensation on the exterior of windows or patio doors can occur at any time of the year or when cool nights follow warm days.
Exterior condensation on energy efficient windows or patio doors is quite common and a natural occurrence. In fact, the presence of condensation can be a good indicator that your windows and patio doors are performing exactly as designed. Energy efficient windows and patio doors are so well-insulated, that warm temperatures in the home are not able to penetrate the insulated glass and heat the exterior pane. As a result, the exterior glass temperature may fall below the dew point temperature of the outside air and condensation can develop. The condensation you may see on the exterior glass surface is similar to the dew that can form on car windshields or on grass after a cool night.
While unsightly, exterior condensation will evaporate once the day warms.