I have ridden in a relative's Volt about ten times. Was prolly just his Volt but the automobile had a severe internal moisture problem that fogged up all windows when it was cold. I told him to take care of it, get this fixed, that it was dangerous driving this way/ Being young and foolish I don't know if he did.
Cold air generally has lower moisture. If you bring some inside where it's warmer, its relative humidity drops, which lessens the condensation on the inside of the windows.
He may have had the ventilation system set to recycle interior air. Any wet in the carpet and breath of passengers condenses on the glass. It needs to be traded with outside air. Yes, it's colder but it just takes longer for the heater to warm things up.