Originally Posted by mizterwizard
Condensation occurs when warm moist air comes in contact with cold surfaces, cools below the dew point and releases its moisture to the surface. Is that right?
Basically correct. But what makes the surfaces cold? And more to the point, what makes the surfaces cold enough for the air to release its moisture (the dew point)? A camper in storage is not fully air tight and will eventually have the same relative humidity as the outside air. But when that camper is closed up, the air is trapped and it only slowly mixes with the outside air, then as the outside temperature drops, the outside surfaces get cold and the now relativity more moist air in the camper causes condensation on those cold surfaces.
Colder air can hold less moisture, so replacing the air that gets warm during the day in the camper with the colder outside air at night reduces the moisture content and the likelihood of condensation. That is why so many people successfully avoid mold by keeping their camper unheated but well ventilated.
On the other hand, since warm air can hold more moisture, then heating the inside of the camper will reduce condensation on the surfaces that get colder.. to some extent. But if ventilation is not sufficient to avoid problems, then a dehumidifier is likely a better option than a heater (if above freezing).
Now if the camper is occupied then the water vapor given off by people makes this worse. Also a heater for comfort is logical.