Understanding Condensation

Why does condensation occur?

Condensation (water vapor or moisture in the air) is a sign of excess humidity inside the home. Condensation occurs when moist air comes in contact with the colder surface, such as a window or mirror. Although the surface of a window may be the first place you notice condensation forming, the window is not the problem. Windows, in this case, merely provide a visible sign that excess humidity or moisture is present in the house. Warm air holds more moisture than cool air. When that warm, moist air comes in contact with a cooler surface, the moisture suspended in the warm air transfers to the cooler surface as condensation.

What causes moisture inside the home?

Indoor moisture in the air is caused by a variety of factors. Common household activities such as cooking, showering, using the washing machine or dishwasher and other activities that use hot water all add moisture to the air. Newer homes are often more subject to condensation because they are constructed with better weather tight materials than older homes. Weather stripping, improved insulation, vapor barriers and modern construction techniques are designed to reduce air leakage. But at the same time, these materials and techniques can also seal moisture inside the home. In newer, more weather tight homes, it is important to be aware of humidity levels and to provide adequate ventilation to reduce humidity levels.


How To Lower Condensation In Your Home

  • Turn on indoor ceiling fans
  • Make sure appliances such as clothes dryers vent outside
  • Use the exhaust fan when cooking or showering
  • Refrain from using humidifiers
  • Install a dehumidifier
  • Open windows and doors occasionally to allow interior moisture to escape.

House with new vinyl windowsNewer Homes and Condensation

Newer homes are often more subject to condensation because they are constructed with better weather-tight materials than older homes. Weather stripping, improved insulation, vapor barriers and modern construction techniques are designed to reduce air leakage. But at the same time, these materials and techniques can also seal moisture inside the home. In newer, more weather tight homes, simply be aware of humidity levels and provide adequate ventilation to reduce interior moisture.

Understanding Condensation

On page video content

Learn more about the causes of condensation on windows in your home, as well as ways to reduce or eliminate it.

Condensation Guide

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