From Leisure Centres to Housing – How to Retrofit Heat Pumps on Complex Public Sites

At Finn Geotherm, we don’t shy away from a challenge — in fact, we specialise in solving them.

For many public sector organisations, the ambition to switch to renewable heating is clear. The hurdle? Existing buildings. Whether it’s a 1970s leisure centre, a listed council office, or a high-occupancy residential site, retrofitting isn’t always straightforward. But it is possible — and we’ve proven it, time and again.

Since 2006, Finn Geotherm has been designing bespoke heat pump systems for exactly these kinds of environments. Our work spans local authority buildings, leisure facilities, visitor attractions, HMOs and housing associations — and we’ve developed a process that turns complexity into opportunity.

What Makes Retrofitting Difficult?

Older buildings weren’t designed with heat pumps in mind. They may have oversized boilers, limited plant room space, poor insulation, or no access to three-phase electricity.

Add in high hot water demand, tight timescales, and funding compliance, and it’s easy to see why many consultants hesitate.

But at Finn Geotherm, we see these challenges as creative prompts — not deal-breakers. We don’t try to squeeze off-the-shelf kits into existing systems. We design around the building and its users. The result is a bespoke, high-efficiency installation that works in harmony with the space.

Case Study: Three Sites, One Vision

When South Norfolk and Broadland District Council needed to decarbonise three very different sites, they turned to Finn Geotherm.

• Diss Leisure Centre required separate systems for space heating and domestic hot water. Our solution used three 210kW air source heat pumps to provide low-temperature heating water, delivering a 70% saving on energy use compared to gas, and two 16kW air source heat pumps for domestic hot water.
• Norwich HMO, housing vulnerable residents, needed heating and ultra-efficient hot water delivery for 8 independent residences with minimal disruption. We worked with Hertz to design and install heat interface units, optimising performance even at lower flow temperatures.
• Council Headquarters needed integrated heating and cooling, but the initial brief proposed the replacement of the gas-boilers-only, whilst the aged chillers remained in situ. We reimagined the system entirely — delivering both functions with a reversible heat pump system that exceeded the original efficiency targets and saved 40% on budgeted costs.

Three different buildings. Three bespoke systems. One shared outcome: dramatically improved energy performance with long-term savings and future-ready infrastructure.

How We Make Retrofit Work

Successful retrofit isn’t just about engineering — it’s about insight. Here’s how we approach it:

• Early Involvement – The earlier we’re engaged, the more value we can add. We’ll assess feasibility, support consultant scoping, and model performance to inform business cases or funding bids.
• Bespoke Design – Every aspect is tailored: heat source, system size, flow temperatures, controls, and spatial layout. Where others say “it can’t be done,” we say “let’s find out how.”
• Respect for Operations – Public buildings don’t close for works. We phase our installs to keep sites live and safe for as long as possible — from leisure centres to community housing.
• Funding Expertise – Whether it’s the Public Sector Decarbonisation Scheme (PSDS) or Low Carbon Skills Fund, we help maximise every pound of available support.
• End-to-End Delivery – No subcontractors. Every Finn Geotherm project is delivered by our own in-house engineers, ensuring consistency, quality and care.

Proving Retrofit Doesn’t Mean Compromise

Public sector organisations are under pressure to decarbonise — but many still believe older buildings can’t support heat pumps.

We’re here to prove otherwise.

Whether it’s installing underground loops at a visitor attraction, integrating ASHPs into cramped housing stock, or retrofitting a Grade II-listed building, we bring the expertise, creativity and passion to make it work.

Every building has potential. And every retrofit is a chance to create something better — not just greener, but more comfortable, more efficient, and more cost-effective to run.

At Finn Geotherm, we don’t just deliver projects. We deliver possibilities.