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Why do I have condensation on my windows?

While window condensation between the panes of glass isn’t normal and can indicate a broken seal or other product issues, windows fogging up on the inside or outside of a home are pretty common.

It’s nothing to worry about.

It just means warm, moist air on the inside of a room touched a cold surface, such as warm living room air heated by the toasty blast of a heater reaching window glass chilled from a cold day outside. Moisture in the air deposits itself on any surface with a colder temperature.

Have you ever pulled a drinking glass from a warm dishwasher and fill it with ice water, only to have rivers of condensation stream down the outside of the glass? Or turn the car heater on full blast on a cold day, only to have the windshield fog up so much you can’t see outside the car? It’s the same thing. During cold weather, window glass on the inside of the home can collect moisture.Condensation on windows

Window condensation happens often in kitchens and bathrooms, too. Windows fog up inside the home as hot water runs from the tap, because it’s created moist air that’s warmer than the temperatures outside the window.

Many homeowners with newly installed double or triple-pane replacement windows are surprised to see condensation, thinking it’s a problem with their new windows, but there’s nothing wrong. In fact, it’s a sign that it’s doing a great job keeping the warm air where it belongs.

Older windows (especially single pane) often didn’t have condensation issues because they lacked the airtight seal we have with today’s modern windows. They would leak warm air around the exterior of the window and vice versa, with cold air coming inside the home, creating a barrier that warmed the outside of the window just enough to prevent condensation.

New windows aren’t drafty, though, and the tighter seal keeps humidity in the home that occurs naturally from normal daily activities (running the laundry or dishwasher, watering plants, using faucets or taking a shower), along with natural humidity coming into the home from the outdoors when people come and go through exterior doors. It’s more energy efficient, but that trapped humidity can lead to condensation, given the right conditions.

If it bothers you, anything that creates drier air and circulation can help dissipate the moisture. Open the drapes or miniblinds and turn on a dehumidifier or use ceiling fans, and the condensation should evaporate. Or crack the window for a few minutes, like you’d do in the car.

One of our trusted manufacturers for the last few decades is Anlin Windows. They’ve created a few videos that some find helpful. So if you like visuals, check ‘em out!

And if your home’s windows are fogging up on the outside, not the inside? Similar rules apply. Window condensation just means the air outdoors is humid and warmer than the window glass. It’s just like dew on a blade of grass in the early morning as the temperatures rise, or moisture on the outside of your cold car when it’s pulled into a warm garage.

It’s the flip side of condensation on the inside of the window – wherever the condensation forms, the glass is colder than the air.

Still have questions, or experiencing window condensation between the panes of glass, not on the outside or inside? A glass repair company can swap out the glass unit, you don’t need a window company since replacing the entire window isn’t necessary. You can also contact the installer if there’s a potential warranty claim. And if DunRite installed your windows? Just give us a call at (602) 456-2227 or email us at info@azwindowreplacement.com. We’ll figure it out together.

Published Oct. 4, 2021

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Please note that we install replacement windows and doors, but we don’t repair them or replace broken glass. Three-item minimum purchase, some doors excluded. Refer to our FAQ and warranties page for details.


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