Turtle, does the insulated window coverings cut down on the condensation on the glass?
Not really. The thermal coverings are affixed to the glass with suction cups. In order to make any kind of significant impact on the condensation, the coverings would have to be sealed so that no moisture-laden air could flow to the windows and condensate on them. Obviously, where the suction cups are stuck to the glass, there is zero condensation. If anything, thermal window coverings increase condensation, same as drapes and curtains can in a home, because the free flow of warm air is restricted.
The only way to reduce condensation is to reduce the level of humidity in the van, which means an air vent (no different, really, than louvers in attic or basement crawl spaces). It doesn't have to be a forced-air vent, either. Moist air will always move to drier air (which is why moisture can work its way through concrete, wood, lots of things in the home). It's called "vapor pressure" and is independent of the airflow. Since the cold air outside is
usually drier than the warmer air inside, simply opening the roof vent a little (1/3 or so) will often be enough to reduce the humidity level to cut down on the window condensation. If it's very humid inside, turning on the vent fan might be necessary for a while, but once the humidity has been reduced, you can shut the fan off or even close the vent if it's really cold out there.]
I generally have little problem with condensation, because I usually have the vent cracked a little. There might be a little down on the lower part of the windshield and side windows, but it's not anywhere near the amount that happens when I forget and leave the vent closed for an extended period of time.
