Why Do Your Home's Windows Fog, and How Can You Fix It?

High humidity can cause window fogging and make your indoor environment uncomfortable. Learn how you can improve your home’s air quality.

June 3, 2021

Condensation on windows is a common problem in many households. The most obvious sign of excessive moisture indoors is the accumulation of moisture on glass window panes and frames. Foggy or icy windows might not inherently be a problem themselves, but they might be an important indicator that there is an underlying problem with your home’s ventilation. Why take a risk? In order to help you stay better informed, we’ll discuss why windows fog and what you can do about it.

What Causes Window Condensation Anyway?

As mentioned above, the primary underlying reason for excessive window condensation is accumulation of moisture. This happens when there’s a high level of humidity indoors. Droplets or water or patches of ice are formed when the difference between the indoor and outdoor temperature is high. 

First, determine where the condensation is forming. Is it on the inside, outside, or between the two sealed double panes of the window? Each has a different reason.

If the "fog" is between the window panes, the seal is broken that holds the insulation gas cavity between a dual pane window. Normally, this cavity is filled with Argon, Krypton, or Air. In the case of condensation between panes, we need to replace the window pane.

If the condensation is on the outside, it means the air outside is warm and humid, and the glass temperature is below the dew point. This would occur in a warm, humid climate, where the air condition inside is very cool and the relative humidity outside is very high.

The third situation is when the condensation is on the inside. That is the target for our discussion below.

While some people might mistakenly think that the windows are the problem, it’s quite the opposite. Usually, warm and moist air moves from the center of the room towards the edges, hitting materials which have a cooler surface temperature. As a result, the air is no longer able to hold enough moisture and it ends up condensing on surfaces such as door handles and—you guessed it—windows. 

Hold on…what causes this humidity then? There are a multitude of factors, such as:

  1. Certain household activities: Things like cooking and bathing can increase the amount of moisture in the air. Plants emit moisture also. This increased moisture results in high humidity.
  2. Inadequate ventilation: If there is an increase in humidity levels within the home and no proper mechanism for expelling the humid air, it will build up and dampen your living spaces. This can cause damage to your home if not taken care of.
  3. Seasonal changes: Winter usually causes a quick drop in outdoor temperature, leading to excess moisture and condensation due to air being unable to hold as much moisture.
  4. Ineffective HVAC systems: You have to monitor your HVAC system! If your HVAC system hasn’t been upgraded or maintained properly it will eventually be unable to remove moisture from the air well enough to prevent humidity from building up. 

How To Prevent High Humidity and Fix Window Fogging

Finally, the part you’ve been waiting for! There are a few important ways to deal with high humidity indoors and ensure your windows never fog again. First, it’s a good idea to install exhaust fans as their sole purpose is to vent moisture outdoors. If you have plants on the window sill of the foggy window, move them away from the window. Opening windows as much as possible will also aid in balancing the humidity levels of your home. If you’ve already tried these fixes, your best bet is to install a high quality dehumidifier. The value of such technology cannot be overstated—it’s a lifesaver for those who can’t seem to get rid of humidity in their homes. It helps keep your home dry and will save you from furniture damage that is likely to occur from too much moisture build up over seasons. Finally, upgrading your HVAC system will yield good results as well. 


At Shipshape, our goal is to help homeowners live more comfortably in their homes and we achieve this through our affordable, state-of-the-art technology. Contact us to know how we can help you upgrade your home.

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