When designing new buildings, there are a number of valid solutions for providing heating and hot water. Each has its own benefits and disadvantages but not all are as energy efficient or sustainable as others.

Exhaust air heat pumps are a relatively new solution which is starting to gain popularity amongst house builders and self-builders alike. An EAHP is an integrated system which provides ventilation and space and water heating as a single, energy-efficient solution. It works by extracting warm air from the building via the ventilation system and reusing it for either heating the space or hot water, as shown in the diagram below.

The heat extracted from the building's ventilation is then used to either heat the space or to heat the domestic hot water which can be fed to your showers and taps. Because the system is able to extract and reuse thermal energy, it is a highly energy efficient solution - as long as the optimum design is achieved. Incorrectly designed or installed systems can reduce efficiency and performance significantly, so always use an MCS accredited installer when installing an exhaust air heat pump.

A well designed and commissioned EAHP system can deliver a COP of around 2.0 - 4.2 (as per the studies referenced above) if all is optimised. It is important to note however that the system needs to be sized correctly and that the control systems must be configured to allow it to operate to its optimum performance.

As a result of this, it is recommended that EAHP systems are only installed in new buildings and that they are incorporated during the construction phase. This is because a series of ducts are required to carry the warm exhaust air throughout the property and this tends to be more cost effective when installed in the build rather than as an after-market retrofit.

The typical installation cost of an exhaust air heat pump is around PS9,000 which includes all ductwork at 1st fix stage, the heat pump unit itself, electrics for the system and connections to the properties services. This is still a very good price point when you consider no gas supplies will be needed in the property, it meets Code For Sustainable Homes renewable energy requirements and it also enables the building to meet the latest Building Regulations ventilation requirements, all whilst reducing running costs and increasing comfort.