Get Rid Of Condensation Before Your Windows Become All Wet

By Glenn Haege

America's Master Handyman

If there is so much condensation forming on your windows that you have to start bailing, it is time to find out what is wrong. Windows are not wells. They do not make water. If they did, the Saudis would buy a billion of them and turn their deserts into lush farmland.

When condensation forms on a window, it is trying to tell you something. Condensation usually forms in three places on a modern window: on the nside of the window pane, on the outside of a window pane and between the panes in double- and triple-pane windows. Each has a different cause and different solution.

Condensation on the inside of a window pane is a sign that airborne water is trapped in the house due to poor air circulation and exchange. This usually means that the furnace is not getting enough air for proper combustion. To test this, tape a piece of kite string to the molding above a window. Make certain that all he windows and doors are tightly closed. Wait until the furnace goes on. After the furnace has been on for about two minutes, open the window. If the kite string goes outdoors, against the screen, you have positive air circulation and do not have a problem.

In the event the string blows inwards, your house has negative air pressure. You do not have enough combustible air in the house and, most probably, you do not have sufficient air exchange for good health. If you have a forced air furnace, you can probably eliminate the condensation by turning on the furnace fan for several hours.

The easiest way to actually fix the problem is to call your heating contractor and have a passive air makeup unit installed. There are also diffuser units to bring in fresh air for homes that do not have forced air heat.

Lately, there have also been complaints from people reporting condensation on the outside of their double pane Low E glass windows. This is not a problem, but a sign that the Low E coating is working and reflecting heat back into the house. This condition usually occurs in the spring and fall, when there are relatively warm ,humid days and cooler nights.

As the relatively warm, moist outside air comes into contact with the insulated Low E outer glass, the pane is actually cooler than the air temperature. Condensation forms on the outer pane, like droplets of water form on a glass of iced tea on a hot summer day. This condensation problem will correct itself as soon as the outside air temperature grows older and less humid.

When condensation forms between the two layers of glass in a double pane window, it is a sign that the airtight seal has been broken, allowing humid air to penetrate between the panes. The only way to fix the problem is to replace the glass. Since seal failure is often caused by an error in the original installation, it will be replaced by the manufacturer if the window is still under warranty.

One final type of condensation occurs between single pane windows and exterior storms. Storm window frames are made with a breathing hole that permits condensation to escape. These breathing holes often become plugged or puttied shut over time. When this happens, moist air becomes trapped and condensation appears. To fix the problem, unplug the holes.

Also consider taking off your exterior storm windows because they are really ineffective. If you have double- or triple-pane window, you don't need them. If you have single-pane windows, you will find interior storm window far more effective. Look in the Yellow Pages for window companies that install interior storms.


To fast answers to many do-it-yourself problems, read Glenn Haege's "Fix It Fast And Easy!" at book and hardware stores. It's $14.95 and it's packed with answers to many of the FAQ on home repair. For ordering info, send e-mail to Electronic Publishing Network at epn@mail.ic.net. In the SUBJECT line of the message, write: Fix It Fast And Easy! BE SURE TO INCLUDE YOUR SNAIL MAIL ADDRESS (Street, City, State, Zip).


If you want to learn more about window condensation, Andersen Windows has produced two excellent brochures, "A Guide to Understanding Condensation" and "There's Condensation on the Outside of My Windows!" To find out how to get copies of these informative brochures, send e-mail to Electronic Publishing Network at epn@mail.ic.net. In the SUBJECT line of the message, write: Andersen Window Brochures. BE SURE TO INCLUDE YOUR SNAIL MAIL ADDRESS (Street, City, State, Zip).