HEAT PUMP GUIDE
www.heatingandventilating.net
Heat pump design: closing the gap between ambition and performance
Rebecca Hogg, technical manager at BSRIA, explains how the rise in heat pump demand is reshaping the responsibilities of specifiers and installers, and what needs to be done to ensure systems deliver in practice
T
he accelerated growth of heat pump adoption is placing greater emphasis on the sector. For specifiers and installers, success depends on aligning design, commissioning, and installation with the real-world conditions found on site. If there is a gap between design intent and in-use performance, this can leave homeowners with higher than projected running costs and lower carbon emissions reduction. In 2024, the UK heat pump sector reached a new milestone, with almost 110,000 units sold, an increase of 48% on the year before . Retrofit projects now represent around half of all installations, alongside growing new-build activity. This represents a major step forward on the road
to decarbonisation, but it also underlines the need for installers to consider each project as a bespoke scenario, and, with the UK’s diverse building stock, there is no single solution that can be applied in every case.
Drivers of growth
Several factors explain this momentum, including the regulatory reform earlier this year through changes to Permitted Development Rights. The allowable unit size has been increased from 0.6m³ to 1.5m³, enabling the use of more varied designs. The previous one-metre boundary rule was also removed, an especially important change for terraced housing, which makes up between 24 and 31% of UK homes . An increase in public awareness has added to this. National media attention and industry-led
Left: Rebecca Hogg, Technical Manager at BSRIA
In recent years, reliance has been placed on
campaigns, particularly from utility providers, have helped to position heat pumps as affordable, viable alternatives to fossil fuel systems. At the same time, the Boiler Upgrade Scheme has accelerated retrofit activity by offering grants of up to £7,500. Together, these factors have created strong momentum but, with increasing pressure on the grid, they also sharpen the responsibility of installers to deliver on promised performance.
Taking a holistic view
For those installing or designing heat pumps systems, accurately quantifying a building’s baseline performance is essential to ensuring correct system sizing and achieving optimal performance. The outputs from building performance measurements will influence the sizing of the heat sink, whether this be an underfloor heating system or panel radiators. In addition to considering the requirements of the heat pump itself, to ensure that the system will perform effectively, installers need a holistic understanding of the building’s fabric and energy profile.
Energy Performance Certificates (EPCs). However, EPCs are primarily assumption-based rather than being founded on physical testing of the building fabric. This means that they fall short of providing the level of accuracy required for effective heat pump system design. Instead, more detailed building performance assessments should be carried out, including evaluations of airtightness, thermal bridging, U-values and overall envelope characteristics. This kind of diagnostic insight is critical to provide a clearer picture of how a heat pump will perform once operational.
Performance in practice
Verifying product claims is as important as assessing building fabric. Energy labels offer a good overview, but installers can also request complete test reports from accredited laboratories. These reports confirm how performance was measured, under what conditions, and compliance with standards such as EN 14511 and EN 14825 for thermal performance, and EN 12102 for acoustics. Independent testing from UKAS-accredited facilities gives the strongest assurance. However, even the most robust systems rely
on correct operation. Without user education, performance may suffer. Installers play a central role in explaining efficient control use, setting expectations on heating behaviour, and showing how long-term savings accrue. Clear handover guidance helps homeowners adapt, ensuring they gain the full benefit of low-carbon heating and close the consumer gap.
Bridging design and reality
Ultimately, heat pump success depends on closing both the performance gap and the consumer gap. In both new-build and retrofit projects, this means ensuring the works match the specification. The technology is no longer niche: uptake is
accelerating. However long-term success relies on evidence-based design, diagnostic testing, independently verified products and strong end-user engagement. For designers and installers, adopting a holistic
approach is the only way to guarantee comfort, efficiency and affordability for clients, while simultaneously making a meaningful contribution to net zero.
20 November 2025
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