Icy Interior

When the Calgary weather turns seriously cold as it did in December, our Cedarglen Living customer support team gets a number of calls regarding ice buildup or condensation on the inside of windows/doors. There are a few causes of condensation buildup that can be expected, and some suggestions to help control this common issue.

Many people have seen condensation and ice form on the inside panes of their windows. While it is most common on single or double pane windows, it is still problem even with triple pane windows (like the ones installed in your Cedarglen home) during extreme cold snaps. This is due to humidity and heat loss through your windows/doors.

In the winter months, the temperature on the interior surface of the window drops due to your heat loss/transfer from the warm air in the interior of your home hitting the cold exterior of your glass. Windows don’t insulate against the cold outside air to the same degree as your exterior walls. The relative humidity also plays a major role in the formation of said condensation and ice build-up. The number of people occupying your home, pets, cooking, showers and water use all contribute to level of moisture inside your home. As you add moisture to the interior environment, it becomes easier for moisture to condense on the cold surfaces we described above thus creating condensation buildup you can see. If the surface is cold enough, the condensing moisture will freeze and turn to ice.

Keeping your interior humidity set as per recommendations from the window manufacture will not completely eliminate the problem but it will make it less likely to occur. We also strongly suggest the use of your bath fan whenever you bath/shower, ventilation fan while cooking, and ceiling fans when the occupancy of your home increases due to parties or gatherings. All of these will help in controlling your humidity level in your home.


Outdoor Temperature, C Recommended Interior Relative Humidity @ 20C
-30 or lower 15%
-30 to -24 15% to 20%
-24 to -18 20% to 25%
-18 to -12 25% to -30%
-12 to -6 30% to 35%
-6 to 0 35% to 40%


By Kenny Marriott