Abstract: “In many large office buildings, hospitals and hotels AC cooling is affected by chilled water generated by a refrigerating plant which rejects its heat to the environment by means of cooling tower water or, increasingly so, by air cooled condensers and adiabatically assisted air-cooled condensers. Hot water for space heating, AC reheat and sanitary purposes is usually provided by a boiler. Using a COAG, the Council of Australian Governments, data base on annual energy consumption per m2 of building, it is shown that significant reductions in the electrical energy, natural gas and cooling water consumption may be achieved when using transcritical CO2 refrigerating systems for building cooling, heating and sanitary hot water, thus saving gas and attendant emissions, and cooling water. It is shown that the specific energy consumption measured in kWh/m2.annum reduces about 30% when retrofitting trans-critical CO2 systems to existing Australian buildings and about 55% in new buildings. These”

Keywords: CO2 refrigerating systems, energy, water, global warming, Montreal protocol, Kigali amendment.