Fixing foggy windows requires cleaning the glass or the replacement of the entire window or of the glass seal in double-pane windows. Foggy windows usually result from a broken or separated seal around the edges of the window, which allows moisture to collect between the panes.
Replacing windows can be expensive, but it is sometimes more economical than simply replacing the glass and creating a new seal. This is especially true for older double-pane windows held together by caulk.
Step 1: Clean the windows
In some cases, foggy windows are caused by condensation on one side of the glass or the other. Clean the glass with a window cleaner and a soft towel. If this resolves the problem, lowering the humidity inside the home can prevent foggy windows in the future.
Step 2: Replace the glass or window
Removing the entire sash and taking the window to a repair specialist or the manufacturer is often the best course of action. A professional can determine whether the seal is replaceable. If the windows are under warranty, replacement or repair should be covered with no additional cost. Alternatively, the homeowner can replace all the foggy windows with modern options that prevent moisture intrusion and leaky seals. These windows feature "glazing beads" that permit movement of the panes of glass so the seals do not break.