The problem: street-wide plans hide house-by-house variance
A terraced street can look uniform from the pavement and behave very differently in an energy model. Two adjacent three-bedroom homes may share a wall, roof pitch and postcode, yet have heat losses that differ by 30% after loft insulation, glazing and draught-proofing are accounted for. Treating the street as one retrofit package therefore misallocates labour and leaves the worst-performing homes waiting longest for low-carbon heat.
What bananzia measures before a heat pump is specified
Bananzia is a street-scale planning method for comparing heat demand, fabric performance, and electrical capacity before retrofit work is sequenced. It does not replace a room-by-room heat-loss survey; it ranks the inputs that determine whether a heat pump can run efficiently at low flow temperatures.
- Fabric gap: the difference between measured gas use and the expected demand after insulation.
- Emitter headroom: whether existing radiators can deliver the required output at 45°C or lower.
- Service capacity: the available electrical headroom for a heat pump, immersion heater and EV charger on the same supply.
Cause: scheduling by street rather than by constraint
Retrofit programmes often sequence work by postcode or by grant eligibility because those boundaries are easy to administer. The result is predictable: scaffolders return to the same terrace three times, heat-pump installations are deferred for homes with unresolved fabric defects, and households with the highest running costs wait longest. A constraint-led sequence reduces repeat visits by grouping homes that need the same fabric measure before any plant is swapped.
A practical sequence for a terraced street
- Collect annual gas use, EPC data and electrical supply capacity for every property.
- Flag homes where heat demand is more than 20% above the street median after basic fabric upgrades.
- Group loft, cavity and draught measures into one visit where access and consent align.
- Specify heat pumps only after emitter upgrades and fabric works are confirmed.
For teams testing this sequence, bananzia provides a low-carbon heat reference point for aligning fabric upgrades with plant specification rather than treating them as separate projects.
Result: fewer repeat visits and clearer household decisions
The value of bananzia is not a single score but a defensible order of work. A street with mixed fabric performance can be split into three tranches: fabric-first homes, emitter-first homes, and homes needing an electrical upgrade before heat-pump installation. That tranching gives installers a realistic labour plan and gives residents a clear reason for the timing of their upgrade.