What to do about condensation?
The cause of the condensation is the walls are below the dew point temperature. If the walls can be made warm enough the problem disappears. Running a fan to circulate air may help to raise the temperature on the surface of the wall.
One other solution is to reduce the relative humidity inside the RV.
The easiest way to do that is to open a roof vent a bit, find the furthest window from the vent and open that a bit. An electric heater near the window will improve that and keep you warmer. I'd suggest a low wattage radiant type, or a small oil filled (if the oil filled can be on a shelf so the air from the window passes over the fins.)
I know opening a vent and window when it is cold seems counter intuitive, but it does work.
Another possible solution is an electric dehumidifier--but the cooler it is the poorer they work. They are generally energy hogs, some what bulky and definitely noisy.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.