Any time you close up a small area and breath, cook and shower, you will get moisture building up. You need to keep one or two roof vents cracked open to let the warm moist air out. Also, any time you shower, open the vent and run the fan on low. Same for cooking...open an vent and run the fan.
I know this is counter to keeping warm, but you have to get rid of the moisture first.
The problem is the dew point (humidity level) of the air inside the RV is higher than the temperature of the windows and frames. The solution is to warm up the windos and frames or lower the moisture leve in the air.
With so much moisture, you will also get some moisture condensing within the walls and this is bad for the insulation and structure.
Amateur Radio Operator (KE5DFR)|Full-Time! - 2012 6.7L Ford Crew Cab Dually -2013 HitchHiker Champagne 38RLRSB - Travel with one Standard Schnauzer and one small Timneh African Gray Parrot