Air source heat pumps are energy efficient and have green credentials, but have not always been suitable for retrofit applications. Robert Lockhart looks at how this is changing.
Air source heat pumps not only deliver energy savings and higher efficiency ratings than traditional technologies, but they also attract financial assistance through the Renewable Heat Premium Payments.

They work by extracting heat from the surrounding atmosphere, which is then passed over a heat exchanger. It is during this process that it is upgraded to a higher, more useful temperature. To minimise the reliance on fossil fuels, the heat pump can also be teamed with solar thermal water heating or a biomass boiler to minimise the reliance on fossil fuels even further.

Existing air source heat pump technologies have generally been promoted as a solution for new builds. This is because they produce a lower grade of heat than other technologies, meaning underfloor heating is the best output for this thermal energy. This is less than ideal for existing buildings, as it requires a lot of work to install an underfloor heating system.

In addition, there has been some scepticism about the effectiveness of heat pumps, particularly when retrofitted to an existing system and during very cold periods.

With these issues in mind, manufacturers have continued to research and develop heat pump technology, allowing these solutions to become almost as adaptable as gas boilers. The most significant advancement is the introduction of inverter technology and sophisticated temperature controls, which enable a heat pump to continuously react to the UK's changing climate and user habits.

Vokèra's AriaPRO is one such example of this new technology. Capable of producing temperatures of up to 60 deg C, these higher temperatures allow this new breed of air source heat pumps to be used with radiators and for domestic hot water when teamed with a hot water cylinder. Although these radiators will still need to have a slightly larger surface area than a conventional radiator, which uses a higher flow rate of 75 deg C, the existing pipework can be utilised for the replacement radiators.

Installing a new inverter-driven air source heat pump is relatively straightforward, helping to reduce time on site which is always a benefit. Little ground work is required, other than the provision of a sound and level base. While there are split systems available, where one part is located outside and the other indoors, plug and play systems are easier to install. In fact, they can be fitted by a heating engineer or contractor rather than a refrigerant engineer. This said, it's recommended that a relevant heat pump course is attended.

With this in mind, those considering moving into air source heat pumps installations should think about becoming MCS approved. Being MCS accredited is likely to be a huge advantage, as most customers will choose those who are accredited for reassurance, as well as to gain access to funding from the Renewable Heat Premium Payment (RHPP) scheme. Part of the criteria for end users to qualify for the RHPP is that the installation is carried out by an MCS accredited installer or contractor.

At a time when the construction of new build homes and buildings are on the decline, and budget cuts are necessary alongside reductions in carbon emissions, existing building stock has to be improved and made more efficient.

Advances in technology are making it easier to use renewable heating systems within the existing framework of a property, resulting in reduced carbon emissions, fuel savings, and lower overheads. With the ease of installation for retrofit projects, it is now much simpler to upgrade existing building stock with air source heat pumps and reap the benefits of this sustainable technology.

• Robert Lockhart is Vokèra's renewables sales manager