Abstract: A humidity control system for an enclosure includes a housing having a process air duct and a regeneration air duct, with return air from the enclosure and/or atmospheric air being supplied to the process air duct and atmospheric air being supplied to the regeneration duct. A desiccant wheel is rotatably mounted in the housing for rotation through the ducts for absorbing moisture in the process air duct and releasing moisture in the regeneration duct. A refrigeration system including a condenser coil in the regeneration duct upstream of the desiccant wheel is connected to a heat pump which includes a heat exchanger and a recirculating fluid loop connected between the condenser coil and the heat exchanger for transferring heat from the recirculating fluid loop to said reactivation airstream.