Foggy Glass In Windows

January 9th 2018
Foggy Glass In Windows

Q:  We have a home with ½” Insul glass window panes that have started to fog up on the inside over the last few years.  We’ve been told the glass is faulty and we should exchange our windows to more efficient.  The frames are vinyl and are still in good condition.


A:  Insulated glass that fogs up is an indication of glass failure.  Over the years, energy efficient glass has been perfected to compensate for nature’s elements such as hot and cold temperatures, direct sun and wind.  Insul glass is made up of two pieces of glass sealed together with 0% relative humidity in between giving clear vision with no fog during the cold weather. 

With aging, some insulated glass with fail at the seal because of severe sun exposure.  For example, on a south elevation continuous expansion and contraction takes place allowing moist air to get between the glass panes.  During direct morning sunshine this moisture condenses on the outside glass panel, leaving a foggy film which is impossible to clean. 

Replacement glass is the only answer when this happens.  It is not required to exchange the entire window.  When replacing glass only, order low E squared with argon - smart glass or as I call it, PowerSmart glass.