How to clean insulated windows the ones that are 3" apart???

IF they're foggy in between the glass that's because the gas has escaped and the seals are broken or leaking. There is nothing you can do about that but to replace the windows. I had same problem but my windows were under warranty, so they had to replace them.

I don't have an answer but I feel your pain. I have a huge front window where the caulking went bad There's only 1/2" space between the windows. The Idiot recaulked while there was condensation between the windows and now I have streaks and spots I can't stand.

Nancy is right. The seal between the glass has failed. The gas (usually Argon) has leaked out and air has seeped in. I know Ace Hardware sells double glass panels and they also install.