Exhaust Air Heat Pumps

By Katie Anderson on September 5th, 2011

Exhaust air heat pumps work using the same principles as air source heat pumps and ground source heat pumps.

The technology uses the wasted warm stale air found in areas such as bathrooms and kitchens, and transfers the air through a series of ducts which run within the walls and floor.

Comprising of a hot water cylinder, heating coil, extract fan, and a heat pump, they are an ideal solution for providing domestic hot water and space heating to smaller housing units, new build flats and apartments via a wet distribution system.

An exhaust air heat pump unit can also work alongside a standard air source heat pump, providing hot water storage and hot water production at times when the air source heat pump unit is not required for heating, usually during the summer months.

Known as ‘fit and forget technologies’, heat pumps are low on noise and compact, and have a life expectancy of around 20 years. Exhaust air heat pumps are used extensively in places like Germany and Scandinavia, where the passive low energy house design is common place.

How do exhaust air heat pumps work?

1. Heat energy within the air is passed over a heat exchanger built into the heat pump unit.
2. The air is taken from the warmer areas of the building and transferred onto the heat pump’s refrigerated circuit.
3. This refrigerant boils and evaporates.
4. Once this refrigerant is in a gaseous state it is compressed.
5. The compressed gas creates heat, and this heat is transferred to the hot water and heating system.

Would an exhaust air heat pump be viable for my home?

If you’re interested in installing an exhaust air heat pump, there’s a few points worth considering, including:

  • Exhaust air heat pumps work extremely effectively during night time hours on an economy 7 electricity tariff.
  • Your property needs to be well insulated.
  • They are the perfect partner for under floor heating, providing low running costs, minimal maintenance and long life.
  • These types of systems are ideal for flats and social housing units.
  • Duct work is required to transfer exhaust air from warm rooms of the house to the water source for heating. Consequently, these types of heat pumps are usually more suited to new build or renovation projects.
  • It’s also worth noting that to ensure the system is incorporated effectively and efficiently, ducting should be designed at planning stage.
  • The Renewable Heat Incentive (RHI) does not currently include provisions for exhaust air heat pumps. The second phase, launched in October 2012, may include this type of heat pump technology.

Costs and savings

The installation of a typical exhaust air heat pump system can cost between £3,000 to £6,000. Running costs and savings will depend on the size of the property and how well insulated it is.

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