Seal Failure: Causes & Fixes for Cloudy, Foggy Windows

If you’re noticing fog between the glass in your windows, seal failure may be to blame. Multiple pane windows have an insulated glass unit, or IGU. The IGU gives the window its insulating properties by maintaining a pocket of air between two panes of sealed glass. If your window is foggy, chances are that the seal in the IGU has failed. And, when that happens, moisture gets trapped between the glass.

An IGU with a broken seal can’t be fixed. Fortunately, advances in technology make today's IGU's much more resistant to seal failure. Donald explains how IGUs work to educate you on your options for repairing or replacing your windows.

Since 2001, CVP Window & Doors have been custom built using advanced technology and high-performance materials for strength, durability, and energy-efficiency. They are industry-leading in thermal performance. Our products meet or exceed EnergyStar® standards and are certified by the American Architectural Manufacturers Association (AAMA), and the National Fenestration Ratings Council (NFRC).

[jlr]

In 2022, we moved into a barely 2 year old brand new house. One of the window became foggy. Those carry a (limited) lifetime warranty. We just had to pay for labor (350$ cdn), and the manufacturer replaced the defective window in spring of 2023. A few weeks ago, when outside temp went below freezing, the foggy haze came back.
Manufacturer floored us by saying "yes, window pane can fog again...".

What could cause a brand new window to experience pane unseal within 2 yrs, being replaced and then replacement unit failing also within 1.5 yrs?
The fact the same window failed twice within 18 months is beyond my comprehension.

[kenweiss]

I have 3- 25-year-old double hung vinyl replacement windows that have double-pane low e argon gas units, that leak when it rains. Water leaks at the bottom corner of the bottom sash during heavy rains. The glass units have no condensation. so I don't think I need to replace the double-pane units. It has been suggested that I place a narrow bead of clear silicone on the outside, along the sides and the bottom where the bottom pane meets the frame, as that could be where there is a leak. Note: the weep holes are working. So I think it might be a defective seal between the glass and frame. If that is the case what is the best way to repair that rain leak?