Reducing humidity in an RVHigh humidity in an RV may be undesirable for health and comfort reasons, in addition to being a catalyst for mold growth. The following is a compilation of dehumidifying methods, some used by various forum members.
Dri-Z-Air is an absorbent material in crystal form suspended in a plastic mesh container above a small plastic bucket. As the crystals absorb moisture they essentially disolve and drop into the plastic bucket as a liquid. The bucket has to be emptied and the crystals renewed periodically, although some members report drying them out and re-using them. This product is sold in Marine Stores and Home Depot.
Calcium chloride will absorb moisture from the air.
A few light bulbs placed in strategic locations can raise the ambient temperature a degree or two and help minimize condensation.
Mechanical/refrigerative dehumidfier units that include a fan and a refrigerated coil. An integral fan draws air over the refrigerated coil which causes moisture in the air to be condensed. These units run off electricity and require a way to drain the condensed water.
Dessicant type dehumidifier units that use a fan to draw air over a dessicant material which absorbs moisture out of the air. A second fan draws heated air over the dessicant to remove moisture and allow it (the dessicant) to continue removing moisture from air. These units run off electricity.
The existing air conditioner(s) in many RVs will act as a dehumidifier. However, this will also cool the interior of the RV, which may be undesirable in cold weather. These units also consume a considerable amount of electricity.
Cracking windows open to allow air flow may be all that is required. However, this may result in the ambient temperature being too low, and it won't be very effective in high humidity climates.