The retrofit problem: heat pumps in narrow back yards
Victorian terraces in cities such as Leeds and Sheffield often have 15–25 m² back yards, single-skin rear extensions and no obvious plant space. A standard air-source heat pump can be squeezed onto a wall, but the noise, defrost plume and planning sensitivity around conservation areas make every installation a negotiation. The harder constraint is the ground loop for a ground-source system: a single home might need two or three boreholes, and neighbours rarely want drilling rigs in adjacent yards at different times. Bananzia starts from that shared physical constraint, not from a catalogue of heat-pump models.
Why the delay comes from pipework, not publicity
The cause is sequencing. If each household commissions its own borehole, the street pays for repeated mobilisation, duplicated thermal response tests and avoidable disruption. Thermal interference between closely spaced loops also lowers performance, so ad hoc drilling can make the second and third installations worse than the first. Shared ground loops solve the physics only when the layout is designed as a block: loop spacing, trench routes, manifold positions and connection stubs need to be fixed before the first rig arrives. Otherwise the cost advantage disappears into reinstatement and permission delays.
How Bananzia sequences the solution
The planning sequence used by bananzia begins with a block-level thermal survey, then a single thermal response test for the shared loop, followed by a phased connection plan. Instead of drilling every garden, the team looks for a redundant service strip, a back lane or a communal parking edge where a horizontal collector or compact borefield can serve 8–12 homes. Each property gets an individual heat pump and metering, while the ground array remains a shared asset. That split matters: occupants control their own heating, but the expensive subsurface work is procured once. The result is fewer rig days, one set of permits and a loop that can be extended as more households join.
What site teams should measure before drilling
- Ground thermal conductivity: a single response test on the shared loop is more useful than assuming a regional default.
- Loop spacing and interference: model the borefield as a whole; 5 m spacing may be adequate in wet sand and inadequate in dry sandstone.
- Trench and manifold access: confirm that a 1.2 m deep service trench can reach the back lane without crossing root-protection zones.
- Phased connection capacity: size the manifold for the final number of homes, not just the first three.
For a terrace of 10 homes, that discipline can turn a fragmented series of domestic retrofits into one coordinated low-carbon heat project. The technical risk does not vanish, but it moves to a stage where it can be measured, priced and managed before the drilling rig blocks the lane.