It's activities inside the rig that are causing the moisture. You need to crack a window or two or open the roof vents somewhat to get the moisture out. The greatest amount of water produced inside an RV comes from it's occupants and their actions. Washing, showering, cooking, breathing and other normal activities produce water, a lot of water. It then becomes an art to operate your roof vents, exhaust fans, windows and doors so that you do not start getting condensing water on the inner surfaces. Watch the upper parts of your windshield closely as it is a single pane glass and will condense water quicker than other surfaces, and definitely quicker than the double pane windows.
Proper moisture management can be a pain at first, but once you get the hang of it, it becomes second nature. Since you already recognize the potential problems you will face, you'll have a short learning curve to be able to get it right.
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