The general consensus for double glazed windows misting over is that it is a bad sign and it indicates the end of life for the windows. It is true in most cases because a window is double glazed if two glass panels are joined together with a gas in between them. This gas in between is the reason that the double glaze and insulation is present and if the seal between the two glass panes are broken then the window would not provide insulation or noise reduction.
Before you can judge and decide whether your double glazed window glass is misting over or not, you should know the causes that can lead up to this particular condition. We would suggest that you always call over professionals if you suspect that the double glazed windows of your house are misting over.
The main cause of double glazed windows misting over is deterioration or wear and tear of time. With continuous wear and tear and temperature outside and inside the windows changing, the gas inside the two glass panels contract and expand. With this happening, the seal between the glasses tends to weaken at first and finally break. Once it is broken, the moisture slowly seeps in causes and causes mist to take over the windows.
Misted over double glazed windows are called failed units when they are not installed the right way. If the glass panes are never sealed the right way in the beginning, you will begin to notice the mist after the first climate change.
The continuous use of harsh chemicals, oil based cleaning materials and harsh solvents to clean the window can break the seal and once it breaks, moisture can easily creep in and mist up the windows.