Boilers, hybrid systems and the energy transition

Full electrification of heat in buildings is the ultimate destination for energy managers, but the journey is not necessarily straightforward – especially in older commercial buildings. James Matthews, director of building solutions at Baxi, looks at ways of making the move to lower carbon heat less daunting, and addresses the role of gas condensing boilers in preparing for the energy transition.

The direction of travel to low carbon heat is clear – the deployment of low-emissions technologies such as heat pumps is critical to making built environment heating systems more sustainable. 

Certainly, more rigid efficiency requirements from the 2025 Future Buildings Standard will look to enforce low carbon heat in commercial new build properties, phasing out natural gas boilers. These new buildings will be designed from the outset for net zero, with heat pumps identified as the central technology to meet the tighter emissions standards. 

So where does that leave the gas condensing boiler? And how can energy managers of older buildings navigate the transition to lower carbon heat?

While gas boilers will be effectively ruled out in new build development, it’s well established that the real challenge is decarbonising our existing building stock. This is because many older commercial buildings still rely heavily on gas boilers and water heaters to provide a readily available energy source for heating and hot water. Moving these harder-to-heat buildings to lower carbon heat will not necessarily be a straightforward process for energy managers, nor is it likely to be one that can happen overnight. 

More realistically, a phased approach will be required to enable energy managers to prepare for the energy transition. So how can condensing boilers support this process? Let’s consider their use both as an early energy efficiency measure and working alongside heat pumps in a hybrid system to deliver lower carbon heat.

Boiler replacement

Where there is an immediate need for more efficient, reliable heating, replacing inefficient or failing boilers with modern condensing models remains a frequent consideration, in our experience. Up to 20% more efficient than standard boilers, condensing boilers can help drive down energy consumption and emissions relating to heating while simultaneously improving comfort levels. 

However, while boiler replacement has its place, this should not be at the expense of planning a net zero roadmap. Instead, use the new boiler installation to make the heating system more efficient and ready for future project phases. 

Where relevant, address the system’s distribution pipework and heat emitters to allow the system to operate at more efficiently at a maximum flow temperature of 55°C (or lower), in line with Building Regulations. This will prepare the heating system for the future integration of low temperature heating while maximising the efficiency of the new boilers by enabling them to operate in condensing mode.

Examining the condition of the heating system, the plant and hardware, including radiators, will also help future-proof the system. Take the opportunity to replace any leaking radiators and ensure any new heat emitters are sized for low temperature heating.

Water quality should also be on the checklist. Impurities can cause scaling and corrosion which will impact the efficiency and performance of the system and could shorten the life of the boiler and other plant.

Finally, if integrating an air source heat pump (ASHP) is the next phase of the decarbonisation journey, ensure that there is adequate external space and electrical capacity. 

Hybrid approach

While a fully served ASHP building will deliver one of the lowest carbon footprints in new commercial buildings, physical space, available electrical power and/or capital expenditure budget are restrictions in older stock.

With the arrival of high temperature ASHPs, like the Baxi Auriga HP+, moving directly to an all-electric solution might be a possibility in some buildings. However, integrating ASHPs and high-efficiency condensing boilers in a hybrid system is often a more practicable solution, as it can overcome project limitations while meeting heat demand more sustainably. Combining a heat pump with a peak-demand condensing boiler in a hybrid system will enable up to 80% of the gas to be decarbonised while reducing risk and overcoming budgetary constraints. 

An added benefit of a hybrid solution is that it requires less electrical demand than a standalone ASHP, potentially removing the need to upgrade the existing electricity supply. 

It should be noted that a robust control strategy is essential to ensure maximum heat pump contribution and optimise the efficiency of both technologies. Modern controls, like the Remeha CHVAC Controller, will provide options for cascading up to eight heat generators – either boilers or heat pumps – or a combination of the two in a hybrid installation. Your chosen solutions provider will be able to offer technical support to achieve a harmonious design that successfully blends the technologies.

Understand the options

The energy transition is a process of moving to low carbon energy sources – and condensing boilers have a role to play in helping support this shift. New condensing boiler installations should be used to lay the ground for the transition and ensure a more energy efficient system. Condensing boilers can also make a valuable contribution in hybrid heat pump systems, meeting peak demand in a well-designed system that helps overcome retrofit challenges and drive the move to lower carbon heat. 

By providing expert technical support, including pre-contract design guidance services, we at Baxi can help energy managers understand the different design options and project phases to arrive at the best choice for each project.

https://www.baxi.co.uk/professional/products/commercial-heating-and-hot-water-solutions