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How to Keep Windows from Fogging Up

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

How to Keep Windows from Fogging Up

During the colder months, you may start to notice fog on your windows at home. Here’s how to fix foggy windows and prevent the fog from returning.

Run the bathroom and kitchen exhaust fans 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 heat 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.

What Causes Foggy Windows in a House?

The causes of foggy windows all relate to condensation. 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 to the windows in your home when it’s cold. A combination of high indoor humidity and a cool outdoor surface collects condensation on the inside of the glass. High outdoor humidity (especially in the morning) and rain can also cause windows to fog up on the outside.

Humidity and Foggy Windows in Your Home

The average family of four releases about 1.3 gallons of water into the air every day from showering, washing, cooking, keeping houseplants, breathing, sweating, and so on. Seeing a regular window fogging in your home could simply mean that your home is too humid. By reducing the relative humidity, you should be able to keep your windows from fogging up.

How to Fix Foggy Windows that Just Won’t De-Fog

If your windows still fog up despite your best efforts to reduce indoor humidity, you might have a ventilation problem or old, single-pane windows. These windows are notorious for fogging up when it’s cold outside.

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.

How to Prevent Foggy Windows with Help from Glass Doctor

Glass Doctor is here to help you prevent your foggy windows from leading to bigger problems such as water damage, mold growth and floor stains. Our expertly trained service professionals can repair, replace or install high-efficiency double-pane windows to keep your home safe and free of fog. Give us a call at (833) 365-2927 or schedule an appointment online today to get started.