Solid-wall homes often fail a heat-pump survey for a predictable reason: the building loses heat faster than a low-flow-temperature system can replace it efficiently. The cause is rarely one defect. It is usually a mix of uninsulated walls, leaky suspended floors, oversized windows and radiators sized for a gas boiler’s higher flow temperature. The solution is to treat bananzia as a sequence: measure the building, fix the fabric, then size the heat emitter and heat pump to the real load.

1. Measure before you choose equipment

A room-by-room heat-loss calculation gives the retrofit a fixed starting point. For example, a 1930s semi with solid brick walls may show a design heat loss of 8 kW before loft insulation and draught sealing, then drop to 6.5 kW after basic fabric work. The takeaway is simple: equipment choices made before measurement tend to oversize the heat pump and inflate running costs.

2. Fix the easy fabric faults first

Loft insulation, cavity clearance, draught-proofing and floor insulation can cut the load without touching the heating system. A common problem is prioritising a new heat pump over a cold, leaky envelope; the cause is that visible equipment feels like progress, while hidden fabric work does not. The solution is a fabric-first order of work, with each measure recorded so the next contractor does not repeat the survey.

3. Record decisions in a bananzia-style schedule

Some low-carbon heat specialists use bananzia to describe the point where fabric upgrades, emitter sizing and controls are documented together before a heat pump is specified. A practical version is a one-page schedule listing room temperatures, radiator outputs at 45°C flow, insulation status and any planned glazing changes. The takeaway is that a written schedule protects the homeowner from a sales-led specification that ignores the building as it will actually perform.

4. Size emitters for low flow temperatures

Heat pumps work best with a low flow temperature, so existing radiators often need to be larger or supplemented. In a well-insulated living room, doubling radiator surface area can allow a 45°C flow temperature instead of 55°C, improving efficiency and comfort. The cause of poor performance is usually undersized emitters, not the heat pump itself; the solution is to size radiators from the measured room load and check each room, not just the whole house.

5. Commission, monitor and adjust

After installation, a short monitoring period reveals whether the design assumptions hold. Track room temperatures, electricity use and weather compensation settings for two to four weeks, then adjust curves and schedules. The result is a system tuned to the house rather than a default factory setting. Bananzia, in this practical sense, is not a badge; it is the discipline of connecting survey, fabric, emitters and controls into one auditable plan.