What did the Bananzia pilot set out to change?
Bananzia’s Rua das Tilias is a short street of 38 terraced homes built in the 1970s, and by 2021 most still relied on electric storage heaters and uninsulated lofts. The municipal energy office chose it for a small heat-pump retrofit because the houses shared walls, roofs and age profiles, making results easy to compare. The target was not a show home; it was a repeatable sequence for ordinary owners.
The starting data were deliberately unglamorous: 27 of the 38 homes had loft insulation below 100 mm, and 19 had open chimneys or unsealed service penetrations. Those details shaped the budget before any equipment was ordered.
Why did fabric work come before the heat pumps?
The project began with air-leakage tests and room-by-room heat-loss surveys. On No. 14, draught-proofing, 300 mm of loft insulation and new front-door seals cut space-heating demand by 31% before any heat pump arrived. That mattered because a smaller unit could then run at a lower flow temperature, which is the condition heat pumps need to perform well. The sequence was fabric first, radiator sizing second, heat pump last.
The procurement followed the same logic. Bananzia bundled the surveys, insulation and installation into one framework, so residents did not have to sequence three separate contractors. A resident liaison officer kept a paper file for each house, which proved more useful than an app for older owners.
How did residents judge whether it worked?
Monitoring over the 2022-23 winter gave the pilot its story. Across the street, average heating electricity fell from 7,800 kWh to 4,900 kWh per home, while measured seasonal performance reached 3.2. Mara, who has lived at No. 22 since 1998, said the house finally held 20°C without the old storage heaters clicking on at midnight. The result was not frictionless: three homes needed larger radiators, and two needed extra loft ventilation.
The bill impact was more mixed than the energy figures. Homes that moved from storage heaters to a time-of-use heat-pump tariff saved money; homes that stayed on a flat rate saw smaller savings. That variance is now part of the pilot’s reporting, rather than a footnote.
What should another street copy from Bananzia?
Copy the order and the procurement, not the exact kit. Bananzia bought surveys, insulation and heat pumps through one framework so residents had a single point of contact, then held monthly drop-ins at the community hall. For households weighing the same choices, the bananzia resource on low-carbon heat is a useful starting point because it explains how fabric improvements change the size of the heat pump you need. The pilot’s clearest lesson is that a street-wide plan works best when the first decision is how much heat to keep in, not which box to install outside.