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January 20, 2010

Understanding Window Condensation

Category | Windows 101

Condensation is the fog that is evident when warm, moist air makes contact with a cooler surface. The same way that moisture appears on the outside of a cold glass on a hot day. If the humidity levels in your home are too high relative to cooler outdoor temperatures, condensation can form on the coldest surface in a room – often the glass of a window or door. While windows and doors are not the cause of the condensation, they are an indicator of a larger problem – humidity.

Humidity is the amount of moisture in the air. Sources include: showers, dishwashers, plants, washer/dryers, humans, pets, cooking, among others. Your home requires a certain amount of moisture, but deciding how much is important. If moisture is visible on your windows or doors, it could be happening elsewhere as well. The key is to strike the right levels of humidity; too much moisture in the air can lead to peeling paint and mildew however air that is too dry can lead to paint, hardwood and furniture cracks.


  • Open window coverings such as curtains and blinds during the day to increase airflow against the glass
  • Keeps blinds up; 3” above the window sill is ideal
  • Purchase a good quality humidity gauge from a home center.
  • Run ventilation fans and/or ceiling fans for longer periods of time
  • Remove insect screens from the windows
  • Ensure exhaust fans vent directly outside and not into the attic.
  • Older vs. Newer Windows

Condensation may be less visible on older windows, because the potential for heat exchange is greater around and through aged frames. New windows, on the other hand are more energy-efficient and airtight which increases insulation and in turn can lower your energy bills.

For more information please visit Householders Guide-Problems and Remedies