Abstract: An environmentally controlled chamber system. The system includes an insulated enclosure having an access door and a humidification/dehumidification chamber enclosure arranged and disposed to provide humidification or dehumidification to the insulated enclosure. The system also includes a refrigerant loop having an enclosure evaporator, a dehumidification evaporator, at least one condenser, a variable speed compressor and piping for directing refrigerant from the variable speed compressor to the enclosure evaporator, the dehumidification evaporator, and the at least one condenser. An electrical heating element is arranged and disposed adjacent to the enclosure evaporator to selectively provide heat to at least a portion of the enclosure evaporator. A method for controlling the environmentally controlled chamber system is also disclosed.