Air con does more than cool the air. It also dries it, which is why it defogs the screen so much faster. If it's too cold in winter, turn the heater on at the same time. That's why we have climate control (of a sort).
I have this "Toyota Air Purifier" that sits on the back shelf. If I turn it on the windows don't fog up. I don't really know what else it does
I had one of thosein my Bluebird. Apparently it's a purifier/deioniser. I thought it was a waste if time, although it did helpmove the air around.