A thermostat and a method include using occupancy sensors, temperature sensors, and humidity sensors to control activation of a cooling function of an HVAC system to dehumidify an enclosure. During times when the enclosure is occupied, the cooling function is activated when the humidity exceeds a first threshold humidity, and continues until the humidity drops below a second threshold humidity or the temperature drops below a first threshold temperature. During times when the enclosure is unoccupied, the cooling function is activated when the humidity exceeds a third threshold humidity, and continues until the humidity drops below a fourth threshold humidity or the temperature drops below a second threshold temperature.