Heat pumps work like a refrigerator, just in reverse. While a refrigerator directs heat to the outside, heat pumps take energy from the air or the ground and transfer it into the living space via the heating system. The transfer medium carrying the heat drawn from the environment is compressed in order to reach the flow temperatures necessary for different heating systems. For example, a heating system with radiators requires temperatures of up to 70°C. Underfloor heating systems, however, manage with a flow temperature of 30°C. This makes heat pumps suitable for both modernisation and new build.