Decarbonisation: A carefully planned journey
Chris Caton, Product Director – Commercial at Ideal Commercial Heating, discusses some considerations to take into account when choosing a low carbon hybrid heating system.
The journey to decarbonising commercial heating is well underway. With ambitious carbon reduction targets, rising expectations around building performance and the continued evolution of heating technologies, specifiers are under greater pressure than ever to deliver systems that reduce emissions without compromising reliability or user comfort.
In a perfect world, every commercial building could immediately transition to a fully electric heating solution. The reality, however, is very different. Existing buildings present a wide range of challenges, from limited electrical capacity and constrained plant rooms through to heating systems designed around high flow temperatures that are difficult to change without extensive refurbishment. Rather than viewing decarbonisation as a single event, the situation on the ground frequently means decarbonisation is a journey; a carefully planned journey.
Hybrid systems provide an effective bridge on that journey between today’s building stock and tomorrow’s fully low carbon future, allowing building owners to make meaningful carbon reductions while working within the practical limitations of their buildings.
What is a hybrid heating system?
In commercial retrofit projects, hybrid heating systems combine heat pumps as the lead source with a complementary heat source supporting peak demand or extreme operating conditions, most commonly high efficiency gas boilers. The two most common configurations for hybrid heating systems are bivalent and parallel.
In a bivalent arrangement, one heat source replaces another at a defined temperature or load threshold. This configuration would typically see the heat pump sized to cover the base load with the boilers required to take over during peak periods when 100% capacity is required. In a parallel configuration, the heat pump operates to deliver as much heat as possible within its optimal performance range. Boilers operate alongside the heat pump during peak demand periods or when higher temperatures are required. This approach allows the heat pump to contribute consistently while maintaining resilience and flexibility. Both approaches have their place, but understanding the operational differences is essential when determining the most appropriate solution for a particular building.
Can all commercial buildings use heat pumps?
There is understandable enthusiasm around heat pumps, and rightly so. They represent one of the most effective technologies available for reducing operational carbon emissions and play a critical role in achieving the UK’s Net Zero ambitions.
However, not every building can be served by heat pumps alone. Many commercial buildings were never designed for low temperature heating. Their existing emitters, pipework and controls often rely upon traditional operating temperatures that can be difficult and expensive to modify. Electrical infrastructure presents another significant challenge. Many sites simply do not have sufficient incoming electrical capacity to support a full heat pump installation without substantial upgrades.
These upgrades can introduce considerable cost, lengthy timescales and disruption to building occupants. Then there’s the space issue. Traditional plant rooms are internal, but heat pumps require external space, careful consideration of airflow and appropriate acoustic design.
Not every site can accommodate these requirements easily. In these situations, hybrid systems allow us to introduce heat pumps as part of the solution, whilst recognising on-the-ground constraints.
Is it just the heat source that needs to be considered in a hybrid system?
Successful low carbon heating design requires us to evaluate the entire heating system. One of the biggest mistakes we can make is focusing solely on replacing the boiler.
Flow temperatures become increasingly important because heat pump efficiency is directly linked to operating temperature. Lower flow temperatures generally deliver higher seasonal efficiencies, but they also require heating circuits capable of operating effectively under those conditions. This means evaluating radiators, fan coil units, air handling units, heat interface units, underfloor heating and process loads rather than simply considering the heat source.
The objective should always be to understand whether system temperatures can realistically be reduced without affecting occupant comfort or operational performance. Only by assessing the complete system can we determine whether a fully electric solution is viable or whether a hybrid approach will deliver better long-term value.
Can domestic hot water run off a low carbon system?
Domestic hot water is often one of the most challenging aspects of commercial heating decarbonisation. Space heating and hot water have very different operating requirements. Heat pumps perform most efficiently when delivering relatively low flow temperatures.
Domestic hot water, however, demands significantly higher storage and distribution temperatures to satisfy both user expectations and hygiene requirements. Attempting to satisfy both demands from a single heat source can lead to compromises in efficiency. For this reason, we’re increasingly seeing decoupled solutions become the preferred
design strategy, with dedicated domestic hot water generation, whether through dedicated air source heat pumps, standalone cylinder systems or highly efficient gas-fired water heaters.
What are the financial implications of decarbonisation?
Perhaps the greatest advantage of hybrid systems is that they allow decarbonisation to happen progressively. Few organisations have unlimited capital budgets and replacing an entire heating system in one project is not always feasible. Hybrid systems allow organisations to install heat pumps alongside existing or replacement condensing boilers, reducing emissions immediately while spreading investment over several years.
This phased approach also reduces operational risk. Building owners can evaluate actual heating demand, monitor system performance and develop future investment strategies based on real operational data rather than assumptions. It also prevents unnecessary oversizing of heat pumps, helping to optimise both capital expenditure and long-term operating costs. Most importantly, it enables meaningful progress today rather than delaying projects while waiting for ideal conditions that may still be several years away.
What sequence should specification take?
When evaluating any commercial heating project, I believe specification should follow a logical sequence. The starting point is always the building itself. Understanding actual heat loss and future building performance provides the foundation for every subsequent decision.
Next comes electrical infrastructure. Is there sufficient capacity today, or can it realistically be upgraded within the project’s programme and budget? The heating distribution system must then be assessed to determine whether lower operating temperatures are achievable. Space constraints, structural considerations and acoustic requirements all influence whether heat pumps can be accommodated successfully.
Finally, there is the operational reality. Running costs, maintenance requirements, occupant expectations and long-term resilience all need careful consideration before selecting the final solution. Only after evaluating each of these factors can we confidently determine whether a fully electric system or a hybrid approach represents the best option.
Supporting the transition to Net Zero
There is no question that heat pumps will play a central role in the future of sustainable commercial heating. However, achieving Net Zero is not simply about replacing every boiler with a heat pump. It’s about understanding buildings, recognising constraints and applying engineering judgement to deliver the greatest carbon reductions in the most practical way.
For many existing commercial buildings, hybrid heating systems represent that practical solution. They reduce emissions, improve resilience, minimise disruption and create a clear pathway towards future decarbonisation. They allow us to put the right technology in the right building at the right time.
