A humidity control system including a heat pump with desiccant coated passive heat transfer devices on both sides of the heat pump and an air circulation system for alternately directing a process air stream to be humidity controlled and a separate regenerative air stream past each side. As desiccant on one side becomes laden with moisture, the air streams are redirected to the opposite sides of the heat pump so the regenerative stream can remove moisture from the first side. Simultaneously, the air stream to be humidity controlled uses the previously regenerated desiccant on the second side.