Abstract: A heat transfer system for a building and the building's appurtenances utilizes a heat transfer medium that obtains heat from environmental panels. The heat transfer medium flows in a unidirectional mode through the system. The heat transfer medium is passed through heat exchangers where the heat values in the medium are exchanged or transferred to water to raise the temperature of the water which is then subsequently used as hot water for appurtenant building uses. The heat transfer system, independently from the ambient heat obtainable from the environmental panels, can also utilize heat drawn from air conditioning units to both cool the air passing through the air conditioners and to heat the heat transfer medium. This heat is then exchanged or transferred to the various water sources for use in the appurtenant building uses. An electrical control system selectively transfers the available heat values to those appurtenant building uses, giving preference to those uses as determined by the operator.