THE HEAT & ENERGY BRIEFING decarbonisation for non-domestic buildings Hybrids delivering practical T
Decarbonising heat in non-domestic buildings is one of the most pressing and technically demanding challenges facing the UK building services sector. These buildings account for approximately 4% of total UK greenhouse gas emissions and around 22% of emissions across the combined domestic and non-domestic building stock. With a large proportion of systems nearing the end of their operational life, there is an immediate need for viable, scalable replacement strategies, as Steve McConnell, director of ICOM and MEHNA, explains
he confirmation of the Future Homes and Buildings Standards (FHBS), due to take effect from March 2027, reinforces the direction in which the sector is moving: higher energy efficiency, tighter compliance and a clear shift toward low-carbon heating and electrification. However, the pathway to achieving these goals, particularly in existing non-domestic buildings, is far from straightforward. Hybrid heating systems, combining heat pumps with gas-fired boilers, provide a technically robust and pragmatic route to bridge this gap. A phased approach like this is particularly valuable in the non-domestic sector, where budget cycles, tenancy arrangements and operational continuity all influence decision-making.
System constraints in the non- domestic sector
A key barrier to rapid decarbonisation is the fact that much of the UK’s non-domestic stock relies on high-temperature heat distribution, often designed for flow temperatures in excess of 70°C. These systems have heat emitters that are not optimised for low-temperature operation, limiting the effectiveness of standalone heat pumps. Retrofitting to accommodate full electrification can also mean resizing emitters, upgrading distribution networks and improving the fabric of the building. In environments such as hospitals, hotels and commercial offices, this kind of disruption is often impractical. Furthermore, peak heating demands in non- domestic buildings can be significant and inconsistent. Designing a heat pump system to meet these peaks introduces challenges around plant size and electrical capacity, not to mention capital cost. As a result, a system that just relies on heat pumps is not always feasible straightaway.
Hybrid systems provide a flexible solution
Hybrid systems offer a flexible alternative by combining a heat pump with a gas boiler. In this configuration, the heat pump is typically sized to meet the building’s base load, operating efficiently over extended periods, while the boiler provides top-up heat during peak demand or when higher temperatures are required. This approach delivers technical and operational benefits, including:
• Efficient base load operation: Heat pumps perform best when operating steadily at lower temperatures.
• Reduced system redesign: Existing emitters and distribution systems can often remain in place, avoiding major retrofit work.
• Lower upfront costs: Smaller heat pump installations reduce capital expenditure and ease constraints on space.
• Improved system resilience: Dual heat sources provide inherent redundancy and operational flexibility.
From a controls perspective, hybrid systems can be highly sophisticated. They can respond to external temperature, real-time energy pricing and grid carbon intensity, switching between or combining heat sources to optimise performance.
Responding to the Future Homes and Buildings Standards (FHBS)
The FHBS represents a significant tightening of regulatory expectations. While the framework maintains familiar compliance metrics, such
8 BUILDING SERVICES & ENVIRONMENTAL ENGINEER MAY 2026
as Target Emissions Rate (TER) and Target Primary Energy Rate (TPER), it introduces a more demanding baseline for both energy efficiency and carbon performance. There is also a strong policy emphasis on electrification and the integration of on-site renewables, particularly solar PV, with a notional expectation of 40% roof coverage in many non- domestic buildings.
It’s important to understand that the FHBS is primarily a standard for new homes and new non domestic buildings, with only limited relevance to existing buildings undergoing certain types of refurbishment. Hybrid systems can support compliance with FHBS in several ways:
• Balanced energy inputs: By combining electricity and gas, hybrids allow designers to optimise performance against multiple compliance metrics.
• Compatibility with renewables: Heat pumps within hybrid systems can make effective use of on-site generated electricity, improving overall system efficiency.
• Flexible compliance modelling: The FHBS retains some flexibility through trade-offs, enabling hybrid systems to be integrated alongside fabric improvements and renewable technologies.
The introduction of delivered energy as a voluntary metric also points toward a growing emphasis on operational performance. Hybrid systems, with their capacity for intelligent energy management, are well placed to respond to this shift.
Supporting wider decarbonisation goals
As the UK electricity grid continues to decarbonise, the carbon benefit of heat pump operation will increase. At the same time,
the gas component of hybrid systems offers a pathway to incorporate low- and zero-carbon fuels, such as hydrogen blends or biomethane, further reducing emissions. From an energy infrastructure perspective, hybrids provide valuable flexibility. By moderating peak electrical demand, they help reduce strain on the grid, an increasingly important consideration as electrification accelerates. The FHBS also introduces more structured
routes for low-carbon heat networks, recognising their role in dense urban and large-scale developments. Hybrid systems can complement these networks, either at building level or within central plant configurations, providing additional flexibility in meeting variable demand profiles. And the growing emphasis on solar PV aligns well with hybrid strategies. On-site generation can be prioritised for heat pump operation, reducing reliance on grid electricity.
The role of policy and incentives
To unlock the full potential of hybrid systems, policy frameworks must evolve to recognise their contribution. We’d like to see financial incentive schemes that include hybrid solutions, reflecting their carbon savings and flexibility. We also believe that hybrids should be treated equally in compliance models, showing their dynamic operation and performance.
The transition to low-carbon heat in non- domestic buildings is inherently complex, requiring solutions that balance ambition with practicality. While heat pumps will play a central role in the long term, the immediate challenge is to decarbonise a diverse and often constrained existing building stock. Hybrid heating systems provide a credible and effective pathway, reducing emissions today while supporting the transition to a fully decarbonised future.
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