This ÖNORM specifies design criteria for heating systems in buildings using heat pumps alone or in combination with other heat generators. Heat pump systems considered include -water - water, brine - water, refrigerant - water (direct expansion systems), air - air and air - water systems driven by electricity or gas. This ÖNORM takes into account the heating requirements of attached systems (e.g. domestic hot water, process heat) in the design of heat supply, but does not cover the design of these systems. This ÖNORM covers only the aspects dealing with the heat pump, the interface with the heat distribution system and heat emission system (e.g. buffering system), the control of the whole system and the aspects dealing with energy source of the system.