Excessive humidity causes multiple problems for RVers: mold/mildew, damage to electronics from water condensate, discomfort, and diminution of insulative properties of items like sleeping bags.

Common causes of high humidity / condensation include:

• living fulltime in the RV
• humid weather
• propane appliances

Humidity due to constant habitation can be reduced with increased ventilation, as with roof vent.

Humidity due to use of propane can be reduced with increased ventilation and the use of more efficient propane appliances.

In some cases a dehumidifier may be necessary. Bitty recommends the Eva-dry Edv-1100.¹⁾ Some users drain the receptacle into a sink or other drain.²⁾ Eva-Dry confirms the 12v adapter for this model passes 12v and not 9v;³⁾ this should make it easier to wire from house power.

Peltier devices are power-hungry; the dehumidifier might best be used as an opportunity load.

Video: teardown of a typical peltier dehumidifier

A “sacrificial window” may work as an unpowered option.⁴⁾