Window University – A Word About Condensation

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Exterior condensation usually isn’t anything to worry about.  Dew on windows is a natural atmospheric phenomenon, and it doesn’t mean your windows are leaking air or malfunctioning in any way. In fact, exterior condensation is a sign of energy efficiency, since it means the outside pane is thoroughly insulated from the heat indoors. Depending on where you live, it may occur just a handful of times per season.

Several techniques are used by manufacturers to increase the condensation resistance of windows. These include windows filled with a convection-limiting inert gas, low-emissivity coatings that increase the temperature of the glass, insulating spacers that reduce heat conduction, and non-conducting sashes and frames

Energy-efficient windows are least likely to have condensation. Their resistance to condensation, however, depends on the indoor humidity level. As the outside temperature drops, the window glass temperature also drops. When moist air comes in contact with the cold glass pane, the moisture condenses and forms water droplets. The variables that effect condensation on your windows are:

  • Inside glass temperature
  • Inside relative humidity
  • Inside temperature
  • Air flow in your house