As with any closed system, one problem sometimes does emerge: trapped moisture.
When water gets trapped between the glass, it manifests itself as fog on the inside.
This moisture cannot escape on its own.
The Spruce / Letícia Almeida
where energy saving does not matter.
What Causes Foggy Glass?
The fogginess may come and go, depending on weather conditions.
The second solution is to defog the glass from the inside-out.
And new IGU panels come with a warranty against failure for some amount of time after installation.
However, it can be difficult to find a company that will replace your IGUs or sashes only.
Window defogging is capable of producing cosmetic results that help improve visibility in your windows.
One benefit of window defogging is that the windows stay in place; they are simply repaired.
No replacement means almost no mess and no landfilling of non-biodegradable window parts.
Since inert gas is replaced with air, some R-value is lost.
Defogging is criticized by some experts but lauded by some homeowners happy with the cosmetic improvements.
Defogging costs less than replacing an entire IGU.
Nor does it restore the thermal performance of the window to its original specs.
How Window Defogging Works
The window defogging procedure expels the water vapor from inside the window.
Then, the window is quickly sealed up again before more moisture-laden air can infiltrate the IGU.
Professional defogging contractors follow a simple procedure usually done from within the home.
Warm weather is more conducive to defogging windows.
Windows cannot be defogged in freezing or below-freezing temperatures.
Usually, two holes are drilled.
Apply Anti-Fog Solution
An anti-fog solution is applied to the inside of the window.
With the moisture gone, most of the stains (calcium and magnesium deposits) are removed, too.
Opening the window is a fast way to erase the fog.
A dehumidifier can also draw out the trapped moisture quickly.
The best option to restore energy efficiency to its fullest is replacing the window.
Starman, Bojan, et al.Primary Seal Deformation in Multipane Glazing Units.Applied Sciences, vol.
4, 2020, p. 1390. doi:10.3390/app10041390
Window Gas Fills: What Inspectors and Consumers Should Know.
International Association of Certified Home Inspectors.
