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Air-source heat pumps transfer heat that is in the outside air into the home. The most common ones transfer this heat into the indoor air, and are called air-to-air heat pumps. There are three main types of air-to-air heat pumps: central, mini-split, and multi-split.

A central heat pump distributes heat and cooling through ductwork connected to vents in each room.

A mini-split heat pump does not rely on ductwork to heat and cool the home. Instead, mini-split heat pumps use a series of one or more indoor heads located throughout the home. An outdoor unit connects to wall-mounted indoor heads by a small bundle of cables, including the refrigerant line. A remote control is used to adjust settings for maximum efficiency, comfort and control.

While the term mini-split can be used to refer to any ductless type of heat pump, it typically refers to a system that only has one indoor head. The term multi-split is often used to describe a heat pump system that has multiple indoor heads.

Not all mini-splits are completely ductless! A ducted mini-split heat pump uses short ductwork to connect a single indoor unit to multiple rooms. In these systems an indoor unit is mounted in the attic, where short ducts distribute air to multiple rooms.

The type of heat pump you choose will depend on a number of factors:

  • Size and layout of your home: Mini-split/ductless heat pumps can be used in homes of various sizes, but they are ideal for smaller homes or homes with an open plan layout.
  • State of your ducts: It’s important to check the ducts of your old heating system. Depending on their size, airtightness, and layout, a contractor may need to do some modifications and repairs prior to installing any new high efficiency heating system.
  • Interest in removing ducts: The ductless design of a mini-split heat pump makes them ideal for installation in homes that do not already have central ducted heating – for example, in homes with electric baseboards or when switching from a boiler system with radiant heating to a heat pump system. If you are interested in removing the ducting in your home to provide you with more headspace or a more efficient utilization of space, installing a mini-split/ductless heat pump will allow you to do so.
  • Zonal heat: The design of a ductless heat pump allows for zonal heating – that is, the ability to set different temperatures in different areas of your home. Zonal heating is an efficient and effective way of providing just the right amount of heat to the areas that are most commonly occupied in the home – such as common living spaces, home offices, bedrooms, and using less heat in areas that are not frequently used. Zonal heating is also useful for homes where the occupants have different heating preferences or for areas of the home that need separate heating controls – like a home with a rental suite.
  • Outdoor temperature: The heat pump you choose should be compatible with your region’s climate. Some models perform better than others in colder winter temperatures.

Other types of heat pumps

  • Air-to-water heat pumps also take heat from the outdoor air, but they transfer it into a liquid distribution (hydronic) system. Air-to water heat pumps can be used for both space heating and domestic hot water.
  • Ground-source heat pumps are another type of heat pump. The steady, moderate temperature of the ground allows these heat pumps to have high year-round efficiency. Ground-source heat pumps often do not require a backup heating system but typically have higher upfront costs than air source heat pumps. Installed cost will vary depending on your site geology and available space.

Did you see a building science or energy efficiency term you did not understand? Check out our glossary.