Comments on the need for integrated design of lighting, heating, and cooling systems. In order to eliminate the penalty of refrigerating the lighting heat, minimize the building non-usable space, and optimize the total energy input, a "systems approach" is recommended. This system would employ heat-recovery techniques based on the ability of the system to minimize the refrigeration and air handling equipment as well as the system energy associated with lighting heat removal. An additional feature of this system is its ability to utilize the same equipment to provide heating requirements of the building. Laboratory tests are cited with illustrations. (RH)