When the temp gets around 35 or below, my windows sweat really bad. It freezes around the frame and I have to scrape it off. Our home is 11 years old, but the windows have done this since it was new. My husband says it is the gas fireplace that we use that does it. I read that too much humidity would cause it, would a dehumidifier help? I have to go around every day and dry the windows. Can you help? -Carol
We get a lot of questions about windows sweating in the winter. Here’s what’s happening and why.
When air warms, it expands which allows it to hold more moisture. As it cools down, it contracts until it reaches the saturation point and releases this excess water in the form of condensation.
Common daily activities in your home—such as cooking, showering, using unvented gas heat, and even breathing—add moisture to the air. When this warm humid air comes in contact with cold window glass, it cools and condenses.
To reduce this problem you need to either lower the amount of moisture in the air inside your home, or prevent it from coming in contact with cold surfaces. Here are some suggestions that might help:
- Run a vent fan in the bathroom when you shower or bath, and leave it on for 15 minutes afterward. Be sure it is vented to the outside and has a high enough capacity for the room. Also, be sure there is a large enough gap under the bathroom door to allow air to enter.
- Vent gas fireplaces, or limit their use, and don’t use older unvented gas space heaters.
- Cut down on cooking that produces excess steam.
- Lower your thermostat to 66°-68° F.
- Be sure your clothes dryer is vented properly to the outside.
- Seal up any cracks around windows.
- Replace older single pane windows with double or triple pane vinyl ones (avoid metal window frames since they conduct cold), or add storm windows to the outside of your house.
- If you are still having problems, consider installing a dehumidifier.
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