Example of seal failure
14 February 2013

Fog Between Panes of Glass in Windows

Example of seal failure

Helpful Customer Questions and Information

Both broken glass and a seal failure can cause condensation between the glass panes or insulated or double pane units. Seal failure may include poor unit design, poor workmanship in the fabrication, poor frame design or simply the age of the unit is too old. They are not manufactured to last forever. External temperature and air pressure can alter the interior of insulated glass by putting additional stress on the seal. With seal failure, the air inside heats up, expands and is pushed out of the unit. After the unit cools down, humid air is drawn inside causing condensation or a “foggy” appearance. In an insulated unit, solar pumping naturally occurs during the change from day to night. During the day sunlight heats the inside and pressurizes the air forcing small amounts out of the semi-permanent seal. Yes, windows do breathe! In the evening the opposite happens and the moist air is drawn in. The silica desiccant installed in the unit helps to regulate how much humidity is allowed to have the unit remain clear. The key components to a well made insulated glass unit are the type of spacer bar used to separate the glass sheets and the quality of adhesive to adhere them together. The best way to correct the “foggy” glass unit is total replacement to be sure that all is properly fixed.


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