Understanding Condensation on Your Windows

Look Familiar?

Ever wonder why condensation forms on your windows—and what you can do to prevent it? Windows serve as visible areas for moisture to condense, warning you that there is too much moisture inside your home.

What is Condensation?

Condensation is the result of high humidity that produces a "fog" once it hits a colder surface. The humidity is caused by excess water vapor in the home. This is commonly seen in a foggy mirror after a hot shower. Condensation usually occurs first on windows because glass surfaces have the lowest temperature of any of the interior surfaces in the home.

What causes condensation on windows?

Whenever there is excess humidity in a home, it manifests itself in the form of condensation on the coldest area of a wall, which is normally the windows. The warmer the air, the more moisture it will retain, so when air in your home comes in contact with the colder glass surface, it is subsequently cooled and moisture is released in the form of condensation on the glass. All homes have a certain level of moisture due to household activities. Activities such as cooking, laundry and dish washing can add up to five pounds of water vapor into the air daily! Other moisture-producing agents include plants, heating systems and humidifiers.

Do windows cause condensation?

No, condensation on windows is not the fault of the window. However, by replacing drafty windows and doors or installing a new roof or siding, you are reducing air flow in your home and making it tighter. Tighter homes actually retain more humidity. Seasonal changes, quick changes in temperature, reconstruction and remodeling can also add excess humidity temporarily into the air.

Can I reduce the condensation on my windows?

Yes. In order to reduce condensation, humidity must be controlled and air movement must be generated. As the exterior temperature drops, the humidity level needs to decrease if condensation is to be controlled.

What steps can I take to reduce humidity in my home?

The two main things you can do are to control sources of moisture and increase ventilation. To decrease or control excess humidity and condensation:

Use exhaust fans in your kitchen, laundry and bathrooms. Run exhaust fans while the humidity-producing appliance is operating or the humidity-producing activity is going on, and let them run a while after the activities have ended.

Vent gas burners, clothes dryers, etc. to the outdoors.

Be sure that the ventilating louvers in your attic, basement or crawl spaces are open and amply sized.

Open fireplace dampers to allow an escape route for moisture-laden air.

Air out your house a few minutes each day. Because outside air usually contains less water vapor, it will "dilute" the humidity of inside air.

If you have a furnace humidifier or other humidifying device in your home, be sure it is adjusted to produce the proper amount of humidity, or turn it off. The humidity produced elsewhere in your home may mean these devices are not needed at this time.

Install ceiling fans to keep air circulating within your home.

If troublesome condensation persists, contact us at 608.643.7914 and we'll send a specialist out for a free, no-obligation inspection of your windows and vantilation.