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Ice Inside Of Windows -Oh no!

Ice inside of Windows?

Cold temperatures are on their way, which means most homes are gonna start showing signs of poor insulation, air sealing, and heating issues. Yay –so fun! (Please note the sarcasm) Every year about this time we start receiving calls from homeowners with the same issues: ice inside of windows and ice building up on the walls of their homes. Don’t worry; here we’ll explain why you experience window condensation and how ice forms on the inside of windows…and how to solve this not-so-fun dilemma.

Window Condensation:

The most common thing homeowners have seen during these colder months are condensation and ice form on the inside panes of their windows. While this mainly occurs with single-pane windows, this can still happen with double pane windows, especially in colder climates. This problem occurs from something called the dew point, which is the temperature point at which water vapor turns into water droplets, which ends up looking like condensation on your windows.

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Ice inside of windows on your home.

Low Thermal Performance:

Many windows, especially North American, single, and double pane windows allow too much interior heat out. Poorly performing windows, during winter months, have low interior surface temperatures because the window is unable to properly insulate against the cold winter air and you guessed it.. you get ice inside of windows. I’m sure you’re wondering, how cold? For a double pane window (normally rated R-3, here’s a blog post regarding R-values here) if the outside temperature is 0F and the inside temperature is 70F, the inside of the window pane will be around 44F. 44 degrees…in your house! Friggin’ cold, am I right?! However, as the outside temperature drops, so will that window surface temp, making condensation more likely. In order to avoid worrying about “freezing” window temperatures, humidity, and condensation build-up mumbo-jumbo, just select a higher-performing window with thermal performance R-5 or higher.

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The air leakage of the window is, indicated in this infrared image by, the blue streak and green blob.


In a larger family, cooking and showering can create plenty of indoor moisture without even trying. As the moisture content of your home increases, so does the potential for moisture to condense on cold surfaces (much like your cold window frames, like we discussed above). Uh-ohs. The colder the surface temp, the more condensation you get. If the surface temp gets cold enough (cause the outside temp is dropping, remember?) that condensation build-up freezes and turns to ice. Trying to keep your humidity levels below 30% can help a bit, but unfortunately, it’s no guarantee to stop your ice-inside-of-windows problem. One way to decrease the humidity levels in your home is by using an HRV (Heat Recovery Ventilator), which removes excess humidity within the home, as well as clears out indoor air pollutants. Oh HRV, my hero!

Air Leakage:

Windows obviously play an important role as an “air barrier” for your home, sealing cold outside air away from your * hopefully* warm interior. If your windows are poorly installed, air leakage will occur, whether or not it is a fixed window (not made to open). An operable window (see this blog post) will leak even more air, especially as they age. Of course, the cold-air leaks surrounding the sash (part of the window that opens/moves) are going to reduce surface temperatures, creating the perfect conditions for condensation and ice to form on the inside of your windows. Ugh! Casement windows and awning (or hopper) type windows have a bit better performing air-sealing performance. However, the horizontal sliders, single hung, and double-hung windows are much more prone to air leakage, causing severe leakage. Double-Ugh! The best sealing windows are European tilt-turn…..better write that one down. *grabs pen*

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European tilt-turn window operation.

Potential Impacts:

Ice inside of windows means that the surface temp on the interior windows is below freezing (aka. 32 degrees –yikes!) which probably means your home is consistently cold and uncomfortable….and paying the energy man an arm and a leg. Not to mention the build-up of condensation and ice on your window can create several problems that include the following:

  • Long term damage to the window unit: Any type of moisture (water or ice) causes swelling and shrinking, warping wood window frames which can lead to glass cracks and increases the potential for air leakage.
  • Health issues: The condensation and ice accumulation can harbor mold and other lung and sinus irritants.
  • Comfort: The constant cold surface temperatures and condensation make your home especially unpleasant and uncomfortable for months on end having major effects of your quality of life –Aint nobody got time for that!
  • Energy costs: Your cold and leaky windows will most likely land you at your thermostat, cranking that baby up in order to keep warm which means your energy bill will also be cranked leaving you cranky….and still cold.

Contact Glo European Windows for any questions regarding full window replacement and ensuring your comfort, sanity, and long-term health of your home and family.