Condensation on the Interior of Window or Patio Door Glass
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Condensation can form on interior glass surfaces when there is too much moisture in the air. If the interior of a structure exceeds certain limits of moisture in the air, the moisture will condense and show up on comparatively cooler surfaces, such as glass.
Interior condensation does not indicate a failure of the glass on your Andersen® window and/or patio door unit.
Understanding Condensation
Windows are typically the coolest areas of interior walls; even if they have storm panels, are glazed with welded insulating glass, have Low-E4® insulating glass or use triple-pane glass. When the warm, room-temperature air comes in contact with the glass surface, the air is cooled and, if there is enough moisture in the air, the dew point will be reached and the water in the air will condense. In cold-weather climates, moist air that comes into contact with the cooler glass surface may cool enough to form frost.
A good analogy is when you have an iced drink on a warm summer day, and the glass has moisture on the outside of it. The warmer air meeting the cooler surface of the glass causes condensation to form.
Recommended humidity levels in winter months should not exceed 30-35%. If these humidity levels are exceeded, you may want to take measures to reduce the interior humidity level.
Ways to Reduce Interior Humidity Level
Checking your ventilation.
Using a dehumidifier.
Turning the humidifier on your furnace down (or off).
Making sure blinds or curtains are open during the day.
Leaving ceiling fans on to promote air movement.
Use an exhaust fan in bathroom areas when showering.
If these ideas do not resolve your concerns with indoor humidity, you may want to consult with a heating and air conditioning specialist. Additional information can be found in Guide to Understanding Condensation.
