[DonovanRig]

Closed cell foam will help. The main problem is that the moisture in the air condnses on the colder hull surface. The solution is to lower the air''s moisture content, its relative humidity. Relative humidity is the amount of moisture air can carry. 100% is the maximum, above that it rains. When the temperature rises, the air can carry more mositure, so even if the moisture content remains the same the relative humidity goes down. You lower the relative humidity by heating the air. However, if you just heat the air, and do not change it, eventually it will absorb more moisture and its relative humidity will rise. The solution is to bring in cold outside air, and heat it. Then the relative humidity will drop. Then circulate the air, so it picks up any moisture condensed on cold hull walls or elsewhere. Then exhaust the air. This can be done by having a heater in the cabin, a fan for air circulation, and a way to force in outside air and/or force warn cabin air out.