Last edited 16 Sep 2016

Exhaust air heat pump

See also Mechanical ventilation with heat recovery (MVHR)


[edit] Introduction

Exhaust air heat pumps collect warm air as it leaves a building via the ventilation system and then reuse the heat that would otherwise be lost to the outside to heat fresh air coming into the building or to heat water. Exhaust air heat pumps operate on a similar basis to other heat pumps such as air source heat pumps and ground source heat pumps and are suitable for providing hot water and heating for buildings such as houses, apartments or flats. Exhaust air heat pumps are often used in conjunction with underfloor heating systems and have been used extensively in countries such as Germany and Sweden.

[edit] Components and system

The typical basic components of an exhaust air heat pump comprise a hot water cylinder, heating coil, extractor fan and a heat pump.

The system works by extracting air through a series of ventilation ducts from moisture-producing rooms such as bathrooms, utility rooms and kitchens. The heat energy in the air is passed over a heat exchanger which then transfers the energy to a refrigerant. The refrigerant boils and evaporates and as a gas, it is then compressed. As the compression takes place, heat is released which is then transferred to the hot water supply, or to the hot water heating system, or to incoming air which supplies non-moisture producing spaces such as bedrooms and living rooms.

As a series of ducts are required through the building to allow the flow of air to and from the exhaust air heat pump, installation tends to happen during the original construction of buildings. Retrofitting into existing buildings may not be practical or cost-effective.

[edit] Benefits of exhaust air heat pumps

The main benefits of using exhaust air heat pumps include:

[edit] Disadvantages exhaust air heat pumps

There are some disadvantages to exhaust air heat pump systems including:

A recent government study is available which considers the efficiency of exhaust air heat pumps installed in social housing based on investigations carried out between 2010 and 2013. Ref DECC, Performance of exhaust air source heat pumps: Summary of detailed monitoring results.

[edit] Find out more

[edit] Related articles on Designing Buildings Wiki.

[edit] External references