Double-pane glass windows almost inevitably develop fog between their panes over time. Fortunately, you can remedy this problem without replacing entire windows. Here’s how to clear up window fog.
How double-pane windows work
Houses built before 1980 had single-pane windows: a lone layer of glass within the window frame. Since then, homebuilders have installed double-pane windows, also known as thermal windows or insulated glass units (IGUs). Initially, the space between the panes was filled with air, but today’s double-pane windows contain an inert gas such as argon or krypton, which provides better insulation.
What causes fogging
As windows age, they are exposed to heat, cold, rai, and wind. Seals around the glass panes fail, allowing the gas inside the panes to escape and outside humidity to invade. This causes fog and even drips. The average IGU loses one percent of its effective seal per year of installed life.
Clearing the window fog
To solve this problem, you don’t have to replace the entire window. Instead, there are two less expensive solutions.
First, check your warranty’s terms. Determine whether it’s still in effect and whether it specifically mentions remedies for fogged glass. You may be able to have the window repaired under the warranty.
To eliminate the fog, you can:
- Replace the glass entirely. This may also require replacing the entire sash that holds the panes, which can be somewhat expensive. Still, the price will be less than the total window replacement.
- Have a window company defog the window by drilling tiny holes in the outside pane of glass. As the sun shines on the glass and warms it, these holes allow the moisture within to dry out. (This procedure can’t be done in freezing temperatures.) The window company may then inject an anti-fog chemical between the panes. They will then seal the holes and repair the seal around the panes to prevent future fogging.
Be aware that the defogging procedure will not replace the inert gas lost between the panes. Double-pane windows defogged in this manner will become like the earliest form of IGUs, holding regular air.
Related – When Is It Time to Replace Your Windows?
