Foggy Window FAQs

Foggy windows, commonly referred to as windows that have 'misted up,' are a familiar sight to most people, whether in their own home, someone else's, or even in a vehicle, especially during cold weather. This common term describes windows that have "misted up." 

Let's learn more about what causes foggy windows, whether it's something you need to worry about, and what you can do to prevent it.

What Causes Foggy Windows in a House?

There's a very simple reason why you get condensation on windows: the temperature and humidity on the two sides of the window are different. If one side of the window is cold and dry and the other is warmer and more humid, you will get condensation. With modern HVAC systems, that happens very often in our homes.

How Do You Prevent Foggy Windows?

Since foggy windows are usually caused by a difference in humidity, the first thing you need to establish is where your windows are fogging up. Is it inside, outside, or between two window layers? The only form of condensation you can actively prevent is when it is inside the home.

If the window is fogging on the inside of your house, it’s probably due to moisture in the home. Anything that causes steam and humidity like a humidifier, showering, or cooking could cause your windows to fog up. 

To prevent your windows from fogging up, here are some things you can do:

• Giving your windows room to "breathe" by opening curtains or blinds a little.
• Using a fan to keep air circulating or turn on the AC.
• Turning off humidifiers, or alternatively, invest in a dehumidifier.
• Using exhaust fans in steamy areas like bathrooms and kitchens.

How to Get Rid of Foggy Windows

There are some steps you can take to prevent fog from clouding up your view and your disposition. These steps vary based on the cause of the fogged windows.

Fog Between the Window Panes

If you notice condensation between the panes of your double-pane windows or doors, it's a sign that the windows are not sealed properly. Moisture has got between the panes, and the window will need to be assessed and repaired or replaced. As the window is effectively damaged, there is no other way to remove the condensation between the panes.

Fog on Interior Panes

If fog builds up on the interior panes of window glass—where you can actually touch it—it’s likely the result of a moisture difference between an indoor and outdoor climate. This usually means the house is warmer and has more moisture inside compared to outside. The windows likely don’t need to be repaired or replaced, but other adjustments might be necessary.

• Cause: Moisture difference between indoor and outdoor climates.
• Solution: Keep track of appliance usage, run fans, or open vents to reduce indoor humidity.

Fog on Exterior Panes

You’ll likely see condensation on the outside of your windows on a cool, humid morning during the spring or summer months. Saturated groundwater creates a sauna effect at a certain dew point. 

Essentially warm, moist air causes condensation to occur against the cool surface of a window pane. This usually means your windows are working effectively and the fog will wear off as the day wears on and temperatures rise again.

• Cause: Warm, moist air condensing against a cool window surface.

Solution: No action needed; the fog will dissipate as the temperature rises.

Are Foggy Windows a Major Problem?

That really depends on where the condensation is and how much there is. If there is enough moisture to drip down, it could eventually lead to moisture-related problems such as peeling paint, rotting wood, buckling floors, insulation deterioration, mildew, and even moisture spots on ceilings and walls.

Conclusion

Condensation on windows is usually not a problem but take a closer look next time you notice it. If it's anywhere other than between double glazing panes, you can probably relax and just wipe up any moisture you find!