Another freeze/thaw season is upon us, which happens to coincide with the presentation of your home fighting against the cold, dry outside – in the form of condensation on your home’s windows. But is condensation always bad? Is ice a problem? Because we get so many calls about condensation at Great Plains Windows and Doors, we wanted to take a quick look at Understanding Window Condensation.

Temperature always seems to be the primary determinant of winter’s arrival. First, we stop hitting 50 degrees, then 40, then…..the dreaded 30 for a high. As the air begins to cool, we often forget that it can’t hold as much moisture. Usually this isn’t noticeable for us as we head outdoors because we grab a jacket and focus on staying warm enough until the car warms up. There’s a major change that’s happening at the same time that has to do with relative humidity.


Relative humidity (RH) is the amount of water in air at a certain temperature compared to the maximum amount of water that same air can hold at a certain temperature. We represent it as a percentage. Complete saturation would be 100%.

The reason this is important to the transition period in the fall/winter and winter/spring periods is that the air on the inside of the house can experience significant humidity gradients between the inside and outside a home. The humidity and temperature swing can cause condensation to occur in many situations with windows and storm doors. Usually we see this on the bottom edge of the glass because cold air falls and creates a moisture trap with the warmer inside air. This is a similar phenomenon to condensation on a glass of ice water in the summer.





The major concern that most homeowners have when calling us about condensation is – Are my windows bad because I condensation? We like to talk through the appearance of condensation with questions like:

  • Is it consistent on all windows in the home?
  • Is there ice on any of the glass or window frames?
  • What is the humidity in the home? In the winter it should be between 30-40%
  • Do you have a whole house humidifier that isn’t regulating well?
  • Has the water started to deteriorate the sash frame due to long term exposure?
  • How long have you been seeing the condensation present?
  • Do you see icy windows or frost between the panes of glass?
  • Have you watched Andersen Windows Guide to Understanding Window Condensation on our website?

Depending on the answers to these questions, we can usually come to a helpful conclusion for most homeowners. Sometimes it is a “wait it out” scenario as the home slowly dries out in early winter. Sometimes it is a faulty weatherstripping or window lock. Sometimes it means exploring replacement windows or replacement doors. If there is active rot or mold because of repeated exposure to window sweat, it may be time to get a low maintenance Perma-shield or Fibrex replacement window to remedy the problem.

If the concern is specifically interior mold from condensation, consult our Solution for Cleaning Moldy Windows post for guidance.

If ice is present and you have insulated windows, you might have a bigger efficiency problem on your hands. Ice usually means the failure of any insulation value in the window or door pane. This isn’t something that has an easy fix. In some cases you can replace the glass in the window with a replacement sash. More often, you’ll need to replace the window and frame entirely to fix the problem. Today’s replacement windows from quality manufacturers like Minnesota’s own Andersen Windows and Marvin Windows are designed in our climate, for our climate.

So, try turning down the humidifier to see if that makes a difference. Once you have a chance to evaluate the effectiveness, let us know if you’re still have problems. We can usually pin down the problem on a visit to your home.

To learn more about window condensation, Andersen Windows has put together this guide to make sense of Window Condensation in the winter months in the Twin Cities.



At Great Plains Windows and Doors, We are all Andersen, All the time. And we’re the only ones doing it this way in the Twin Cities. Come see what we have to offer.

If you need some help navigating the window replacement process or looking to replace your entry door in St. Paul or Minneapolis, look no further than Great Plains Windows and Doors. Our residential window experts are here to help. Find out more at or call us today at 651-207-4571.