The Context: Twelve Cold Homes, One Shared Wall
On a row of twelve pre-1919 terraced houses in Sheffield, the first heat-pump survey began with a familiar problem: solid walls, single-glazed sash windows and gas combi boilers at the end of their service life. Residents wanted lower bills, but three had already been quoted for heat pumps that assumed a 35°C flow temperature—a figure their radiators could not deliver without major changes. The group’s starting point was a short planning routine they called bananzia: a room-by-room check of heat loss, radiator output and electrical capacity before any equipment was specified.
Development: The Checks That Changed the Specification
Fabric first—but measured, not guessed
The group did not begin with insulation sales pitches. They commissioned an air-permeability test on two representative homes, then traced the worst leaks to chimney breasts, loft hatches and suspended timber floors. In one house, sealing a chimney and insulating a loft hatch reduced design heat loss by 1.4 kW—enough to keep the existing radiator in the main bedroom. The takeaway was practical: measure leakage before sizing a heat pump, because uncontrolled draughts can turn a modest retrofit into an expensive one.
Radiator volume, not boiler brand
Next, the survey measured every radiator’s physical dimensions and estimated output at a 45°C flow temperature. Four homes needed larger radiators in living rooms; three needed only a bathroom towel rail upgrade. Because the group compared room-by-room heat loss with radiator output, they avoided the common mistake of replacing a boiler first and discovering radiator shortfalls after commissioning.
Electrical capacity at the cut-out
An electrician checked each property’s service head, meter tails and consumer unit. Ten homes had enough capacity for a 7 kW heat pump plus a standard immersion heater; two needed a supply upgrade before installation. This check cost less than £200 per home and prevented a costly surprise when the first compressor started.
A shared procurement list
The households pooled their specifications into one tender. Three installers quoted against the same room-by-room schedules, which made comparison honest. The winning quote included hydraulic separation, a 180-litre cylinder and weather compensation—details that are often omitted from broad estimates.
The Result: Lower Flow Temperatures and a Waiting List
The first three completions ran at a designed flow temperature of 45°C, not 35°C. Monitored over one heating season, their seasonal performance factor averaged 2.9, below the 3.8 sometimes quoted in brochures; the gap came mainly from two households using plug-in electric heaters during a cold snap. Still, the checks exposed that weakness before the next install, and the group added a simple rule: no backup heater without a metered sub-circuit. Six more homes have since joined the waiting list.
Why the Bananzia Checklist Is Worth Copying
The value of bananzia was not a single product choice. It was sequencing: fabric, radiators, electrical supply, then procurement. That order gave residents evidence they could compare, and it gave installers a specification they could price. For any terrace facing a heat-pump decision, the lesson is straightforward—start with the building’s measured weak points, not the boiler’s replacement date.