Great topic and let me add this- Wife and I took our new to us Sundance to Florida a few days after Christmas last month. We left Pittsburgh at around 20 degrees and drove to Orangeburg, SC at 65 and rain to sleep at the Cracker Barrel. When we got into the coach everything, and I mean EVERYTHING was soaked- Walls, ceiling, windows, fridge, even the canned goods in the pantry! I had to take a microfiber and dry as good as I could while running the fantastic fan and opening all of the windows. Imagine after 10 hours of driving in cold and rain all I wanted to do was sleep it off, but had to deal with this instead. Made for an absolute miserable evening, Even the bedding was damp. I'm not sure if riding with the vents open would have helped but usually I have the roof vents cracked when traveling but didn't this time because it was SO cold when we left home.
Major lesson learned.