Air source heat pumps use refrigerant technology to harness the latent heat from the outside air and convert this to the higher temperatures needed for heating the inside. Even in the UK the outside air contains a reliable level of heat energy and can be extracted at temperatures as low as - 15C.
Air Source Heat Pumps can be fitted in applications where a Ground Source Heat Pump isn't possible e.g. flats or apartments and offer the extra benefit of being installed outside and thus freeing up extra living space on the inside.
During the summer months the process can be reversed when used with an underfloor heating system to provide cooling. The excess heat in the living space is withdrawn to the outside to leave more refreshing and cooler rooms.