Vinegar and water will keep your car windows from freezing overnight.
Just mix 3 parts of white vinegar to 1 part of water and put it in a spray bottle and mix the solution together and then spray your windshield and car windows with the vinegar and water mixture.
Spray the windows on your car with the white vinegar and water before it freezes and in the morning or when you come out form work your windows should not be froze over.
A Coworker recommended this home remedy for keeping car windows from freezing overnight or anytime and it works.
Also if you need to remove ice from Windshield the vinegar and water will also melt the ice off your windshield faster.