The majority of failed sealed
units are found on the sunny side of the property.
When strong sunlight hits a window, the increase in temperature
makes the air between the panes of glass expand, increasing pressure on the glass and on the seals.
At night or on a cold cloudy day, the temperature drops and so does the pressure
between the panes of glass, causing a suction effect.
This gradual flexing and pressure this cycle causes may eventually break the seal around the panes
of glass. When this seal is breached, moisture carried in the outside air is drawn into the sealed unit
which causes condensation, or fog between the sheets of glass. In most cases the a seal break
will take years to occur , if ever.
In the past when it did occur, a complete replacement unit was the only viable
solution. Although sealed units are made with water absorbant desiccant within the bar that separates the
sheets of glass, when the seal fails this eventually becomes saturated. This allows water droplets to form on the glass
and “misting” begins. In the early stages of visible failure, a mist may appear and disappear
on warm days. But as more and more moisture is drawn into the sealed unit the fog becomes permanent, eventually staining the
glass on the inside. Once this staining occurs the only option may be to replace the unit, which may be expensive.
But if caught early, an inexpensive option exists!