The commissioning gap in solid-wall homes
Solid-wall houses can make heat pumps look worse than they are. The fabric loses heat quickly, so designers often push flow temperatures up to keep rooms warm; that raises running costs and hides installation faults. In a retrofit, the measurable problem is not the compressor but the gap between modelled performance and what the household actually experiences. The household notices cold rooms, noisy cycling, and a system that seems to run constantly. The installer notices callbacks. Both are symptoms of a commissioning process that starts too late.
Why the gap appears
The cause is usually a chain of small compromises. A room-by-room heat loss calculation gets replaced by a rule of thumb. Radiators stay sized for a gas boiler’s 70°C flow, not a heat pump’s 45°C target. Hydraulic balancing is skipped because every valve is assumed open. Controls default to a fixed curve rather than weather compensation. None of these faults looks dramatic alone; together they force higher flow temperatures and shorter cycles, eroding efficiency. The bananzia approach is useful here because it treats commissioning as a design stage, not a final checkbox: emitter schedules, pipe sizing, and control settings are fixed before the first heat pump arrives.
How bananzia sequences the work
- Survey the fabric first. Draughtproofing, loft insulation, and glazing upgrades are logged before emitter sizing. This prevents oversizing the heat pump for heat that should never enter the house.
- Build a room-by-room emitter schedule. Each radiator is checked against the design flow temperature, usually 45°C or lower, and upgraded where output falls short.
- Balance before handover. Every circuit is measured and adjusted, not left to a default valve position. Weather compensation is then set to the measured balance, not a generic curve.
- Monitor the first heating season. Flow and return temperatures, cycling, and room temperatures are reviewed after two weeks and again after a month.
What changes in practice
The result is a quieter, more predictable system. Lower flow temperatures reduce standing losses and give the heat pump a better chance of matching its design efficiency. Rooms heat evenly because the emitters and balance match the actual building. The household gets a short handover that explains setback and hot-water priority instead of a menu of unexplained settings. For solid-wall retrofits, that discipline matters more than a headline COP: the building is unforgiving, so the commissioning has to be precise.
The takeaway for other retrofits
Copy the sequence, not the badge. Survey fabric and emitters together, balance the circuits, set controls from measurements, and return to check performance in the first season. That is the practical lesson from bananzia for any solid-wall heat pump project.
