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Fact or Fiction: You Can Prevent Foggy Windows

A foggy piece of glass with the caption "Fact or Fiction: You Can Prevent Foggy Windows."

When the weather turns cold outside and you start heating your home, you’re likely to see “fog” form on the windows. Is this an unavoidable phenomenon, or can you prevent foggy windows? Glass Doctor® is here to provide the answer.

What Causes Foggy House Windows?

Condensation is to blame for the fog you see on your windows this time of year. Picture an ice-cold drink with water beading up on the outside of the glass. This process occurs because the air cools immediately next to the glass. Since cold air can’t hold as much water vapor as warm air, the moisture condenses on the cool surface.

The same thing happens with the windows in your home during the fall and winter. A combination of high indoor humidity and a cool outdoor surface triggers condensation to form on the inside of the glass. High outdoor humidity in the morning, and if it rains can also cause windows to fog up on the outside.

How to Keep House Windows from Fogging Up

The fact is you can prevent foggy windows! Don’t always blame the window glass for this phenomenon—it’s merely the first cool surface that excess moisture condensates on. Instead, take foggy windows as a clue that your home may be too humid.

According to the American Society of Home Inspectors, the average family of four releases over 2.5 gallons of water into the air every day from showering, washing, cooking, keeping houseplants, and even breathing. By reducing the relative humidity in your home, you should be able to keep windows from fogging up. Just follow these tips:

  • Run the bathroom and kitchen exhaust vents when you shower and cook.
  • Crack the windows open when it’s relatively warm and dry outside to “air out” your home.
  • Make sure your clothes dryer vents to the exterior.
  • Turn off portable and whole-house humidifiers. If necessary, run a dehumidifier.
  • Fix plumbing leaks as soon as you notice them.
  • Keep your furnace set to the daytime temperature overnight to help keep windows from fogging up in the morning.
  • Keep curtains open and run the ceiling fan to increase the circulation of warm air around the windows and help condensation evaporate faster.
  • Seal exposed soil in the basement or crawlspace with a vapor barrier.
  • Consider installing a whole-house heat recovery ventilator to exhaust moist, stale air to the exterior and replace it with clean, pre-heated air from outside.
  • Install storm windows or films over single-pane windows to increase their insulating ability. Storm windows help keep the glass warmer while window films block humid indoor air from reaching the glass. Both techniques work to prevent water from condensing on your windows.

Prevent Foggy Windows with Help from Glass Doctor

If your windows still fog up despite your best efforts to reduce indoor humidity, you might have old single-pane windows. These are notorious for fogging up when it’s cold outside because there’s no buffer between warm, moist indoor air and cold, dry outdoor air.

If you have double-pane windows and the fog appears between the glass, the window seal is likely broken and moisture has gotten inside. Old age, improper drainage around the window, and years of exposure to harsh sunlight can cause the seal to break. The only way to address this problem is to replace the glass in the window or sometimes, the entire window.

To prevent foggy windows from leading to bigger problems such as water damage, mold growth, and floor stains, let Glass Doctor repair your double-pane windows for you this winter. We’ll install high-efficiency double-pane glass that insulates better and stops fogging.

To learn more about our window glass repair options, please contact Glass Doctor today.

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