My car is in an underground carpark at home so all good for me there...but when I am out at the observatory in winter for the cold nights (like tonight will be!) with the car parked outside, I have one of those reflective windscreen covers used in Summer, I put it on the outside of the windscreen and secure tightly against the glass using the doors..in the morning when I want to leave, I take it off, turn on the windscreen demister and all good. The only down side is the cover is usually covered with a layer of ice, which obviously melts so I can't put it in the car, so I brush off at least some of the ice and leave it inside the observatory site shed, you would leave it at home in the garage I guess?
Mike