I have a large double pane picture window that is foggy.

Some window folks can reseal it, but you have to take it out and to them in their shop.

T here is a way, but it's one for the professionals really, Bur you could try running a hair dryer all around the seal of the window to see if you can find where it is leaking from, and maybe dry out the inside????

I don’t know about defogging it but you can hide It. I have a bay window next to my bath tub. I didn’t want to loose the light and at the same time I had to do something. I went to Lowe’s and got a clear but designed roll of a think plastic covering. I sprayed a little water on the inside of the glass and then put the plastic on it. it has been the for 3 years and it worked great!

The Family Handyman posted an article regarding this very issue this week. Check out their website because I cannot get my Mac to copy and paste for me! Darn thing.

A double-pane window that is fogged means the argon gas has seeped out and moist air has taken its place. On a budget, I'd try heating the window with a warm hair dryer to remove the moisture. This may take a while. Then I'd silicone caulk the edges on both sides because the leak may be a pinhole, anywhere. If that doesn't work. . . sorry, I've got nothing else except replacing it.

https://www.doityourself.com/stry/defogging-a-double-pane-window

The seal has broken and the inert gas (usually Argon) has leaked out and air has got in. There are companies that found a niche market. They drill holes in the corners of the glass, spray a desiccant in between the glass panes then seal the holes. It MAY solve the fogging but the insulating factor of the glass is compromised and the fogging may return. Replacing the glass panel is the best solution not the while window. I know Ace Hardware sells double pane glass panels and they also install.

Hello,

No, there is nothing you can do except have the glazing units replaced! You can disguise the appearance by using a window cling or sticky backed plastic on the windows.