A shared heat pump and new windows cut bills by half in a year.
A year ago, Patricia Molloy was spending about £140 a month heating her two-bedroom flat on the Fernhill estate in north Calder, and she still wore a coat indoors through much of January. This winter, her bill is averaging £68, and the condensation that used to stream down her bedroom window each morning has gone. Her experience is typical of the estate as a whole: across 186 homes, average heating costs have fallen by 52 per cent in twelve months.
The change came from two pieces of work carried out together. The housing association that owns Fernhill replaced the estate’s ageing gas boilers with a shared ground-source heat pump system, drawing warmth from 48 boreholes drilled beneath the playing field. At the same time, it fitted new double-glazed windows and insulated the cavity walls and lofts of all six blocks. The total cost was about £4.2 million, two-thirds of it funded by a regional decarbonisation grant.
Why heat and health go together
The project was designed with health as much as energy in mind. Before the work began, a survey by the association found that almost a third of households on the estate reported damp or mould, and more than one in five had a member with asthma or another respiratory condition. Local GPs had flagged Fernhill as an area with high rates of winter chest infections among older residents and young children.
“Cold, damp homes are one of the most reliable ways to make people ill. If you fix the building, you take away one of the causes rather than treating the consequences again every winter.”
That is how Dr Simon Achebe-Ward, a GP at the Fernhill health centre who helped design the survey, described the link. The practice has recorded a noticeable drop in appointments for respiratory complaints from the estate this autumn compared with the same period last year, though he cautions that one season is too short to draw firm conclusions.
Residents describe the change in more immediate terms. Families with young children say they no longer have to choose between heating one room and the whole flat. Older residents report sleeping better and moving more easily around their homes. Several said they had been able to stop using portable electric heaters, which are expensive to run and a significant fire risk.
How a shared heat pump works
The system works by circulating fluid through pipes sunk about 120 metres below ground, where the temperature remains a steady 10 to 12 degrees all year. Heat pumps in a plant room at the edge of the estate concentrate that warmth and send hot water through insulated pipes to each block, where it feeds radiators and hot water cylinders. Because the heat pumps run on electricity, they produce far less carbon than the gas boilers they replaced, especially as the regional grid adds more wind power.
Sharing the system across the estate brings economies of scale. A single plant room is cheaper to install and maintain than 186 individual heat pumps, and the boreholes can be drilled once rather than in every garden. Residents pay for the heat they use through a meter in each flat, at a tariff set by the association below the cost of equivalent gas heating.
The windows and insulation are what make the system efficient. Heat pumps work best when supplying steady, low-temperature heat to a well-insulated home, and the association’s engineers say that installing the pumps without improving the buildings would have saved residents only about a fifth on their bills.
Lessons for other estates
The project was not trouble-free. Drilling the boreholes took three months longer than planned, and some residents spent several weeks with temporary heaters while the new pipework was connected. A handful complained that the new radiators felt less hot to the touch than the old ones, which required a series of visits to explain how the system keeps rooms warm by running continuously at a lower temperature.
The housing association’s director of property, Naomi Lightfoot, said the biggest lesson was to treat insulation and heating as one job rather than two. The association plans to apply the same approach to three more estates in Calder and Harrow over the next five years, subject to grant funding. Other landlords in the region have already visited Fernhill to see the plant room, and the regional health board is considering whether to fund similar work on estates where GP data shows high rates of cold-related illness.
