Here are the images of my window (currently it's 18F/-8C outside, 74F/23C inside):

Ice forming on the edges of the window Condensation on the edges of the window

Now, this condensation / ice forming gets even worse - on some days whole bottom of the window from the first picture is completely covered with ice / condensation.

My assumption is that heat loss happens here because edges of windows are not properly insulated. Is that assumption a sound one? This doesn't happen on any other windows in the room - condensation / ice always forms on these two windows.

If I am correctly identifying the problem, few questions:

  1. What should I use to improve insulation and prevent heat loss here? Generic caulk?
  2. If I am to use caulk, should I apply it inside or outside? Both?

1 Answer 1


Ice forms in that location because 1) heat is lost where the two panes of glass are connected by the metal frame, and 2) cold air sinks to the bottom of the window opening. I don't see any red flags that indicate air leakage or other serious issues. The fact that the entire glass pane frosts up at times reinforces that position. You have simple heat conduction happening, with little or no air movement from exterior to interior.

I've lived in Minnesota for 25 years, and what you see there is nearly unavoidable in extremely cold weather. It's a result of heat loss through the window and excess moisture inside, and it's the reason window film was invented. I realize that the idea of applying film annually isn't terribly appealing, but it's probably your best bet here, short of replacing the windows. Only low-e glass panels and ultra-modern sealing and insulation, coupled with very good indoor humidity management, will completely prevent ice formation.

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