How a 36-Home bananzia Pilot Sequenced Heat Pumps Before Winter

Map the estate by fabric band before choosing heat pumps

The problem on many 1970s estates is not a shortage of low-carbon heat equipment; it is that each home loses heat differently. A 36-home bananzia pilot began with a room-by-room survey of walls, lofts, glazing and ventilation before any heat pump was specified. Two identical-looking houses can need different flow temperatures, radiator sizes and running costs, so the pilot sorted homes into three fabric bands rather than treating the block as one system.

Example: the leakiest band needed loft top-ups and draught-proofing before a heat pump could run efficiently at 45°C. Takeaway: fix the envelope first, because a heat pump sized for an unimproved house will be oversized after basic insulation.

Size the shared ground loop around measured peak demand

The cause of expensive shared-loop schemes is often a design based on boiler-era assumptions. The bananzia team measured hot-water peaks separately from space-heating demand and added a buffer tank to smooth short draws. That kept the ground loop smaller than a nameplate-based estimate would have allowed.

The project team used the bananzia low-carbon heat checklist to compare measured demand with manufacturer data before ordering equipment. The result was a loop sized for the block’s actual winter peak, not for every radiator running at once.

Run billing and controls as a trial before full rollout

Residents distrust new heat systems when the first bill arrives without context. The pilot ran a four-week controls and billing trial in six homes, using room sensors and heat meters to show how set-back periods and hot-water timing changed consumption. The solution was a block-level statement that separated standing charges from usage and explained what a cold snap would do to costs.

This step matters because heat-pump running costs are sensitive to controls, not just tariffs. A simple schedule change can move more than a headline tariff comparison suggests.

Commission for the first cold snap, not a mild test day

The final problem appears in callbacks: a system that passes commissioning in October can struggle in January if flow temperatures and defrost cycles are untested. The pilot kept a checklist for the first sub-zero week, including flow/return temperature checks, buffer-tank stratification and resident-reported comfort.

That cold-weather review produced a shorter snag list and fewer emergency calls than the local benchmark for gas-to-heat-pump conversions. Takeaway: build a cold-weather review into the handover. That is the practical difference between a bananzia pilot that looks good on paper and one that keeps homes warm when demand peaks.