Condensation on new windows can be frustrating, but new windows often seal air leaks and a tighter house means elevated humidity.

Condensation can occur on windows, in crawlspaces, on air conditioning ducts and even in attics. Lots of things around your home also contribute to the addition of water vapor in the air. Uncovered ground in crawlspaces, indoor plants, laundry hung out to dry, cooking activities, aquariums, humidifiers, etc. all add water vapor to the air. Add to this the natural humidity and you can see that condensation is a very common thing.

Water is forming on your new windows because one of several things is happening. The temperature of the inner glass surface is at or below the dew point for the amount of humidity in your inside air. The humidity of your indoor air is quite possibly much higher now with your new windows because the air leaks around your old windows were eliminated once the new windows were installed. Cold, drier air that leaks into homes from the outdoors lowers the relative humidity indoors. This is one reason people have static electricity problems in drafty homes during the winter months. Dry air makes it very easy for the static sparks to transfer from your hands to grounded objects.

Make sure crawlspace soil is covered with high-performance vapor retarders. Minimize the number of indoor plants you might have. Run kitchen exhaust fans if you boil lots of water when you cook. If you have a vent-free fireplace, limit its use as it produces vast amounts of water vapor when it burns natural gas. Be sure to operate bathroom exhaust fans during bathing activities and pipe this humid air directly to the outdoors.

You may also be able to minimize or eliminate the condensation by creating air movement around the windows. Air blowing over the interior glass will act just like the defroster does in your automobile.