When a broken window seal occurs, you will see fogging or even dripping between the two panes of glass. It’s easy to think this is on the outside or that it can be cleaned — it can’t, it’s in between two pieces of glass sandwiched together. Seal failure is common in the mountains especially due to our altitude, exposure to the elements and the intensity of the sun. There isn’t a way to clean in between the panes of a thermopane window. To solve this issue, the glass will need to be replaced.