2006 Sentra, blown AC unit. Do not intend to fix it due to the costs involved. Its been sub-zero for the last 2 days. Today morning, got into the car to drop the kid off to the school and noticed that both the windshield are frozen INSIDE. This happened for the first time so took me a moment to register. Sprayed the deicer and cleaned the windows. The windows fog all the time during rain or cold days (until the car warms up). I wonder what options do I have to keep the humidity low inside the car, other than leaving the windows cracked open. Googlefu tells me that I could use kitty litter gel crystals in a sock. I have never used these (no pets). Are these any different than the silica in silica packets? I ask because I would like to know if they will make a mess after absorbing moisture. Then I would leave such sock in some kind of flat container. Any other ideas? Thanks in advance.