For UK organisations looking to set their buildings on the path to net zero, the journey will be less straightforward for some than others. Improving the way older, harder-to-heat historic buildings, like Aldenham School in Elstree, are heated can be particularly challenging.

Aldenham, which dates back to 1597, offers both Boarding and Day options for girls and boys on its expansive historic estate.

When the ageing boilers serving one of its boarding houses, Paull’s House, reached end of life, the forward-looking School was keen to explore solutions other than replacement to improveits green credentials. Alongside this goal, the requirements were to ensure an efficient heating and hot water service for the boarders, connect the system to the neighbouring science block, and complete the work within the summer shutdown period. Reliability was also key as neither Paull’s House nor the science block could be without hot water.

Complex retrofit issues in the draughty 16thcentury building meant that the School had already had to rule out use of renewable heating technologies.

“We were working with an extremely old building in which parts of the fabric date back to the 16thcentury,” explained Tony Albon, the School’s Head of Estates. “So, we decided to call in the heat experts for advice.”

A successful partnership was built with heating manufacturers Baxi Commercial Solutions. Tony and Karl Mahon, Aldenham’s Bursar, heldlengthy discussions with the Baxi Commercial Solutions teamwho carried out multiple site visits to understand the exact requirements before presenting the feasible options.

“It was clear that the most viable solution to meet all our needs was a Combined Heat and Power (CHP) and condensing boiler system,” Tony continued. “Not only can this solution meet the space heating and large domestic hot water requirements more efficiently at Paull’s House, reducing energy demand, but it produces electricity at lower costs for use within the building.”

CHP produces useful heat and electricity at the point of use in a single, highly efficient process. Rather than rejecting ‘waste’ heat to atmosphere like traditional power stations, CHP captures it and feeds it into the building’s heating network to produce useful thermal energy.

This energy can then be used to provide primary space heating and/or pre-heat for domestic hot water within the building. By simultaneously generating heat and onsite power, the system can typically achieve a total fuel efficiency of 85-90%, double that of conventional technology. That means primary energy savings of up to 30% and an emissions reduction of around 20%, compared with traditional generation.

“The Baxi team really took the time to explain the proposed solution,” said Tony. “They also arranged visits to sites where similar Baxi CHP systems had been installed. It was great to be able to see the CHP in situ, hear the building owners’ own experiences and come away with an accurate, realistic idea of the energy saving benefits.”

After completing a feasibility survey and a final assessment of the heating and hot water demand at Paull’s House, a Remeha R-Gen SenerTec Dachs G5.5 CHP was selected, supported by three Potterton Commercial Sirius three 110kW wall hung condensing boilers. The project contractors were Keeble Environment Services.

Both the CHP unit and the ultra-low NOx stainless-steel boilers are compatible with the proposed introduction of 20% hydrogen into the gas network, enhancing the sustainability of the installation.

“The collaboration has resulted in the best possible solution for the School, meeting all our objectives,” Tony added. “The CHP team has been by our side throughout the project.They also brought in their technical, training and commissioning experts to support us and the contractor.”

Baxi’s specialist team will be carrying out all future maintenance and servicing as well as providing training to ensure that the CHP continues to deliver as designed.

“Our boarding students have commented on the improved comfort levelsin Paull’s House, as have the teachers in the science block,” Tony continued.

“Sustainability was an added driver, and we anticipate an annual reduction in electricity costs of around £3,500 and a saving of over 6,000 kg of carbon from the CHP. It’s a fantastic result – we have great plans for further projects with this partnership.”