The problem: a cold terrace with a gas boiler
On a February morning in Bananzia, the Richardson household on Willow Row recorded 14°C in its front room while the gas boiler ran continuously. The terrace is typical of the district: solid brick walls, narrow back yards, and a boiler replacement history that varies house by house. The issue is not that residents oppose low-carbon heat. It is that a single air-source heat pump is awkward to site and expensive to install when every home on the row makes a separate decision.
The cause: fragmented decisions and hidden costs
Bananzia’s first retrofit attempt stalled because the work was organised at the wrong scale. Between 2019 and 2023, the three streets now in the pilot replaced 41 separate gas boilers, each with its own installer, flue route and warranty. Only nine homes added loft insulation in the same period. The result was a patchwork of upgrades: newer boilers locked households into fossil heat for another decade, while uninsulated walls pushed running costs higher. The cause was not a missing technology but a missing sequence.
The solution: a shared heat loop with staged fabric work
The Bananzia pilot connected 68 homes to a low-temperature district heat loop, supplied by two air-source heat pumps at the former depot on Mill Lane. Insulated pipes run under the back service alley, avoiding trenching through front gardens. Before connection, each home received a fabric survey: loft insulation where access allowed, cavity fill for the few suitable walls, and draught-proofing around doors and windows. Heat emitters were then sized room by room. The project’s design notes, published through bananzia, describe the loop as a retrofit enabler rather than a simple fuel swap, because it lets households upgrade fabric and heating in a planned order.
What other neighbourhoods can copy
- Map the block, not the house. Bananzia’s survey recorded wall type, boiler age, flue position and garden access for every property. Engineers grouped homes by connection cost, which revealed that 19 houses could share one pipe spur.
- Sequence fabric before heat. Insulation and draught-proofing were completed first, so the heat pumps could run at lower temperatures. That reduced radiator upsizing and kept plant capacity smaller.
- Use a visible anchor. The depot plant room became a toured demonstration site. Residents could see the equipment, ask about noise, and check monitoring data before signing a connection agreement.
The result: lower bills, fewer interruptions, a replicable model
In the first monitored winter, participating homes used 22% less delivered energy for heating than the previous gas baseline, after accounting for weather. Street-level works were compressed into two phases, cutting repeated road closures. The takeaway is not that every neighbourhood needs an identical loop. It is that Bananzia’s block-level sequencing turned an intimidating retrofit into a set of manageable decisions: survey first, fabric second, shared plant third.
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