Abstract: An apparatus to improve human comfort by selectively humidifying or dehumidifying the air within a building to comfortably allow a higher temperature during summer conditions, and for selectively humidifying the air when desired at certain times of the year is provided. The apparatus includes a humidification/dehumidification unit that can provide either humidified or dehumidified air on demand; a sophisticated thermostat that includes a humidity control system, to monitor and maintain both winter and summer humidity control; and a blower fan control system to quietly distribute conditioned air throughout the home using the existing blower fan and ductwork.