The disclosure is directed to a growth chamber apparatus and method of operating the same. The method is concerned with operating a growth chamber of the type having a plurality of electric lamps and at least one cooling coil through which a cooling fluid is circulated to maintain a desired temperature or humidity level within the chamber. The disclosed method comprises the steps of providing an absorption type refrigeration unit and utilizing at least a portion of the cooled process fluid output to supply the cooling fluid for the coil; and, conducting the heat generated by the lamps to the absorption type refrigeration unit to supply at least a portion of the energy required to operate the unit. The disclosed apparatus is particularly arranged for carrying out the noted method.