Air Source Heat Pumps


The basic insights underlying air-source heat pump (ASHP) technology have been around since the early 1800’s when scientists discovered that objects could be rapidly cooled by evaporating liquids under low pressure. These insights were eventually refined to form the vapour-compression cycle that underpins heat pump technology much of modern refrigeration.

To understand heat pumps it is worthwhile to note that natural phenomena often have a direction. Water falls downwards. Air flows from high pressure to low pressure. Heat energy flows from hot to cold. However, just like a water pump or an air compressor can reverse that direction, so can a heat pump. A heat pump can take heat energy from the ambient outdoor air (i.e. “air-source”) that may be as cold as -25ºC and “pump” it into a building at room temperature. A key advantage is that, by “pumping” heat energy rather than burning a fuel, it is possible to get efficiencies that are several times greater than conventional approaches to heating. Using cold air to provide heating seems counter-intuitive, but it really is the same basic technology that is used in a refrigerator or air-conditioner with the small difference that a heat pump can be used to provide both heating and cooling.

The modern electrically-driven variable-capacity cold-climate ASHP is relatively new technology that has been rapidly developed over the last decade alongside innovations in compressor technology, control and refrigeration. The Living City Campus’s Archetype Sustainable House is used to evaluate the best ASHPs on the market today. They are relatively straightforward to install and use only a third of the energy of electric resistance heating, making them a very cost-competitive retrofit option in electrically-heated buildings.