PARTNER FOCUS
Air-to-air heat pumps: the next big opportunity for installers?
Air-to-air heat pumps are moving from the margins of domestic low-carbon heating into a more formal place in the UK market. With MCS updating its standards to bring air-to-air systems into scope, installers are likely to see growing interest from homeowners looking for effi cient heating, comfort cooling and lower-disruption retrofi t options.
"Eurovent Certifi cation is one of the bodies off ering certifi cation services for MCS 007 heat pumps. Its role is to assess products against the scheme
requirements, manage testing and audit activity, and support publication of approved performance data for certifi ed models."
F
or contractors, the opportunity is attractive but technically specifi c. These are not simply “air conditioners that heat”. Correct application depends on heat loss, air
distribution, refrigerant design, condensate management, sound, controls, electrical supply and commissioning. MCS recognition adds another layer: installers will need to understand the competence expectations attached to certifi ed installations.
How air-to-air diff ers from air-to-water An air-to-air heat pump transfers heat between outdoor air and indoor air using a vapour-compression refrigeration circuit. In heating mode, the outdoor coil acts as the evaporator and the indoor unit rejects heat directly into the room. In cooling mode, the cycle reverses, and the indoor unit removes heat and moisture from the occupied space. This makes the design approach diff erent from an air- to-water heat pump. There is no hydronic emitter circuit to balance and no radiator or underfl oor heating fl ow temperature to optimise. Instead, comfort depends on indoor unit selection, fan performance, throw pattern, room geometry and control strategy. Most systems provide space heating and cooling, with new technological advances increasing the number of heat pumps that also provide domestic hot water (DHW). Typical domestic confi gurations include single split, multi- split and, in larger homes or light commercial applications, small variable refrigerant fl ow (VRF) systems. The main components are the outdoor unit, one or more indoor fan- coil units, refrigerant pipework, insulated condensate drains, controls, isolators and suitable electrical protection. The technology is not new: reverse-cycle air conditioners
have provided heating in homes for many years. What is changing is the recognition of air-to-air heat pumps within the UK’s renewable-energy certifi cation and incentive landscape. Air-to-air is particularly suited to dwellings without wet
central heating, electrically heated homes, fl ats, extensions, garden rooms, converted lofts and open-plan areas where rapid response is desirable. It can also support summer resilience as overheating becomes a more common concern.
Key design checks for installers An important stipulation for MCS is the requirement for whole
building heating. The starting point therefore remains a room- by-room heat loss assessment. Capacity should be checked at relevant outdoor design conditions, not only at nominal catalogue points. Installers should also consider minimum modulation, part-load operation and the likelihood of cycling in smaller rooms. Oversizing may deliver fast warm-up, but it can reduce comfort, increase noise and shorten run times, leading to lack of performance and increased running costs. Indoor units should be positioned to wash air across the occupied zone without blowing directly at seating or sleeping areas. Ceiling height, furniture layout, door positions and stairwells all aff ect air movement. Poor indoor unit positioning can lead to many issues, including draught complaints, cold spots or stratifi cation. In multi-room properties, installers should avoid assuming that one high-wall unit will heat a whole dwelling evenly. Zoning, door closure and internal heat transfer need to be discussed clearly with the customer. Refrigerant pipework is another critical area. Pipe length, height diff erence, added charge, insulation, fl are quality, pressure testing, evacuation and leak checking must follow the manufacturer’s instructions and F-gas requirements. Condensate should be designed for both cooling and defrost conditions, with suitable fall, insulation where needed, and consideration of freezing risk or nuisance discharge. Outdoor units require adequate airfl ow and service access, with attention to recirculation, prevailing wind, snow or leaf build-up, wall vibration and neighbour noise. Sound power data should be reviewed during selection, while sound pressure at sensitive locations will depend on distance, refl ections, mounting and operating mode. Electrical design should confi rm circuit capacity, protection, isolation and any DNO notifi cation requirements. Controls are equally important. Set-points, fan modes, timers, occupancy patterns, zoning and remote access can make the diff erence between an effi cient system and one that
24 September 2026 •
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