Condensation in double pane windows: more than just a pain

Is your view of the world through your window a little foggy? It could be condensation that has formed between the panes of your double pane windows. This is not just an annoyance, but a sign that you may have serious window problems.

Why is my window foggy?

Glass expands and contracts with temperature changes, just like any other material. The phenomenon is called thermal pumping, and over time this movement can cause leakage in the seal that keeps the gas or air trapped between the panes. When this happens, humid air leaks into the space between the panes and forms water droplets that appear as condensation.

Dealing with condensation

Condensation is the primary sign that the integrity of the window's seal has been compromised. When this happens, the window is not insulating as well as it should, affecting the energy efficiency of your home. Also, the condensation can cause etching of the glass over time. Both conditions are undesirable, and must be dealt with as soon as possible.

You should first determine if your window is still under the manufacturer's warranty. If so, contact the manufacturer for a replacement. If not, there are two ways to deal with the condensation issue: repair or replace.

Defog or replace?

Double pane window repair is a process called defogging. A hole is drilled in the window, a solution is sprayed in, and the moisture is vacuumed out. A defogger device is then inserted in the hole to release moisture. This procedure is controversial, with companies that perform defogging claiming to restore the window to full performance. Other experts dispute those claims, maintaining that full thermal efficiency cannot be restored with this procedure. Window repair practitioners typically price defogging at half the cost of glass replacement.

If you elect not to use defogging, a local glass company can replace the glass in your leaky window, which is also cheaper than replacing the entire window assembly. Note that defogging is not an option for sliding glass doors or other tempered glass panes, as tempered glass will shatter when drilled.

If you purchase good quality double pane windows for home installation--those with a solid warranty from a reputable manufacturer--they can save you money on repair or replacement down the road when they eventually succumb to time and the elements.