Condensation on windows is an easy phenomenon to explain: condensation on the exterior surface of windows is caused when the temperature inside the home is much cooler than is the outside temperature, and temperature on the interior surface occurs when the temperature inside the home is much warmer than it is outdoors. The difference in temperature causes the moisture in the air to cool down, condensing from its gaseous to its liquid state.
Causes of Condensation on Double-Pane Windows
What's less straightforward, though, is the cause of condensation on double-pane windows. Typically, condensation on the interior side of double-pane windows is caused by a crack in the window seal.
Condensation cannot occur, even with extreme temperature differences, without the presence of moisture in the air. Since double-pane windows are typically sealed in such a way to prevent moisture from getting between the panes, fog or condensation on double-pane windows could be a sign that they're in need of repair.
How to Remedy Double-Pane Window Condensation
If you notice condensation between your double-pane windows, a broken seal is the most likely cause. The three easiest ways to remedy the problem are: attempt cleaning the windows to ensure that the discoloration is actually condensation and not buildup, replace the windowpanes individually or replace the whole window.
The latter choice is expensive, but can be beneficial in the long run if the windows are very old. Usually without replacement, condensation cannot be corrected.
Reduce Humidity in Your Home
Once you've removed existing condensation on windows or replaced the windows, it's important that you take preventative measures to ensure that condensation buildup doesn't strike again. One way to prevent condensation is to reduce the humidity levels in your home.
You can do this by running vent fans in the kitchen and bathroom and limiting the use of moisture-producing machines like the dishwasher. You can also prevent condensation by investing in good window caulking and weather-stripping and improving the air circulation within your home, particularly around your windows.