Thermal Bridging on Windowpanes

April 10, 2023


DaleH_thermal_bridging_IMG_0557 (003)

Photographer: Dale Hugo  

Summary Author: Dale Hugo   

We had a very dense fog develop during the overnight hours of October 31, 2022, and on the morning of November 1, condensation was visible on every window in our house. On the front bow windows (shown above), condensation pillars were surrounded by window glass that was perfectly clear. These are argon-filled, double pane glass windows that I had installed a couple of years ago. installed 2 years ago. I first thought that the seals had broken, and moisture was condensing inside between the panes.

However, further examination revealed that the condensation was on the outside of the windows. So why the clear regions at the perimeters of the panes? This is likely a result of thermal bridging -- the frames, which are vinyl, warm up faster than the glass. It demonstrates that heat moves from warmer to cooler areas and so when the glass near the vinyl was warmed above the dew point, it lost its frosted-coating look -- the moisture had evaporated.


Arlington Heights, Illinois Coordinates: 42.0884, -87.9806

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