Yes heat pumps work in poorly insulated buildings. Reposting this information as numerous commentators under my last heat pump post keep peddling the myth that heat pumps require highly insulated buildings.
Heat pumps can work in any building if sized, designed and installed correctly. Many uninsulated homes and buildings are already heated to comfortable temperatures with heat pumps, as shown across multiple case studies, including an uninsulated stone church.
A building loses heat through the walls, the windows and the roof when it is colder outside than inside, as shown by the stylised arrows in the figure below. The upper panels show an outdoor temperature of 10C, coloured purple, and an indoor temperature of 20C, coloured red.
Without insulation, shown in the left-hand panels, heat loss is higher – indicated by the larger arrows – and the heat input must similarly be increased, in order to maintain a steady indoor temperature.
At lower outside temperatures – shown in the lower panels – more heat is being lost, for a given level of home insulation. Yet as long as the heat input from a heating system is equal to the heat loss, the building will still retain its indoor temperature.
This means that for a poorly insulated home, a larger heat pump is needed, just as a larger gas boiler would be needed to reach the required heat input. For any home, the system is usually designed for the coldest day of the year.
Field research from Germany confirms this stylised representation. One of the longest running field studies of heat pumps in renovated properties shows that extensive renovations and insulation upgrades are not necessary to install a heat pump. Good fabric efficiency will keep running costs down, but this is also true for homes heated by gas and oil boilers.
Heat pumps do usually operate at lower “flow temperatures” to maximise efficiency, which means the water pumped to the radiators in a house will have a temperature closer to 50C or below. Although gas boilers also operate more efficiently at lower flow temperatures, they are typically set to provide water at much higher temperatures of 70C or more.
This means the radiators connected to a heat pump system will be cooler, potentially requiring larger radiators or underfloor heating to achieve the same indoor temperature. Research shows, however, that radiators are often oversized to begin with – and that, as a result, not all radiators may need to be replaced.
Moreover, the market already offers high-temperature heat pumps that can reach flow temperatures of 65C and higher. These can be operated with existing radiators.
Furthermore, the UK government’s electrification of heat UK demonstration project showed that the efficiency of high-temperature heat pumps nears that of standard heat pumps, because they only need to run at higher flow temperatures on the coldest days.