A major benefit of transcritical CO₂ refrigeration is the gliding temperature available when cooling the transcritical fluid from the final high temperature at the completion of compression to as low a temperature as practicable. This property may be exploited when requiring simultaneous cooling and heating in building air conditioning applications. The CO₂ compressor discharge can usually heat enough water for heating, reheating and hot water purposes thereby obviating the need for a boiler and its fuel supply. Using USA Department of Energy data for energy consumption by USA office buildings it is shown that CO₂ cooling reduces primary energy consumption, energy cost, water consumption at the buildings and CO₂ greenhouse gas emissions by an estimated 55%, 57%, 75% and 53% respectively in the existing building stock when coupled with a 25% reduction in supply and return duct air velocities, and exhaust duct air velocities. In the case of new buildings these beneficial reductions would be about 63%, 65%, 79% and 61% respectively. Incorporation of energy recovery from exhaust air and economizing cycles will produce additional reductions in all three areas. The absence of cooling towers eliminates the danger of Legionella disease. The absence of HFC refrigerants eliminates the danger of high GWP fugitive gases escaping.