I noticed this the past few days during the rainstorms and cold days. After parking my car for hours, I notice that the windows fog up inside on their own (when I return from work for example). I seldom use the AC and heater, but if I do I always turn it off, but I do leave my vents open. I've never had any of my cars do this, at least not that I can remember. Is something going on with the vents? Sound normal to you? Maybe I like this car so much that I worry too much and notice every little thing about it...? And yes, the car is completely powered off. Thanks.