Air Source Heat Pumps

Air Source Heat Pumps (ASHPs) are innovative devices that efficiently provide both heating and cooling for buildings. They work on the principle of transferring heat from the outside air to the interior of a building, even in cold weather. Here’s a concise explanation of how ASHPs operate:

The ASHP Process:

  1. Absorption of Heat: ASHPs consist of an outdoor unit (the evaporator) and an indoor unit (the condenser). Even in cold weather, there is heat energy present in the outdoor air. The ASHP’s evaporator coil absorbs this heat energy.
  2. Heat Transfer: A refrigerant fluid circulates within the ASHP system. As the outdoor air’s heat is absorbed by the evaporator coil, it causes the refrigerant to vaporize, turning it into a low-pressure, low-temperature gas.
  3. Compression: The low-temperature gas is then compressed by the ASHP’s compressor, located in the outdoor unit. This compression process raises the temperature and pressure of the refrigerant.
  4. Heat Release: The high-temperature, high-pressure gas is then sent to the indoor unit, where it passes through a coil. Here, the refrigerant releases the heat it absorbed from the outdoor air, warming the indoor space.
  5. Distribution: The warm air produced by the ASHP’s indoor unit is distributed throughout the building via a fan or air ducts. This provides comfortable indoor temperatures during the heating season.
  6. Reversibility: ASHPs have a unique feature that allows them to work in reverse during the cooling season. By simply reversing the flow of refrigerant, they can extract heat from the indoor air and release it outside, providing cooling.


Air source heat pumps offer an energy-efficient and versatile solution for both heating and cooling needs. By efficiently transferring heat from the outdoor air to the indoors (or vice versa), ASHPs contribute to reduced energy consumption and lower greenhouse gas emissions, making them a sustainable choice for climate control in homes and businesses.