A systemic failure in heat pump installation practice is costing UK households an estimated £20 million a year in avoidable heat loss and the government has now been forced to acknowledge it publicly.
The admission came last week at the Chartered Institution of Building Services Engineers Decarbonisation Conference in London, where the Department for Energy Security and Net Zero confirmed that sub-standard external pipe insulation is widespread across UK heat pump installations. The average affected household is losing £43 a year as a result.
The numbers get worse the further out you look. WattsWatt has calculated that if external pipe insulation failures go unaddressed, heat pump households will collectively lose £82 million a year once the government’s 400,000-installations-a-year target is in full swing.
The root cause is straightforward. External pipework connecting heat pumps to homes is routinely being insulated with materials designed for indoor use.
When that insulation becomes saturated (as it inevitably does outdoors) the water travelling through those pipes loses heat before it ever reaches the house. The heat pump then works harder to compensate, drawing more energy and pushing up bills.
“We first became aware of the issue when households complained their heat pump had stopped working as well as when it was first installed,” said Lisa Malyon, co-founder and CEO of WattsWatt. “It turns out their external pipework had been insulated with basic grey insulation designed for inside, and it was soaked through.”
Critically, the problem has a regulatory blind spot at its heart. The MCS’s (Microgeneration Certification Scheme) MIS 3005-I installation standard does not specify what type of insulation should be used on external pipework. MCS directs installers to manufacturers’ instructions, but those instructions tend not to specify the requirement either. The result is a gap that has quietly been costing households money for years.
Chris Ridge of the Thermal Insulation Contractors Association was blunt about the stakes. “In the battle to win public trust for heat pump technologies we simply cannot afford the additional energy losses caused by incorrectly specified and installed thermal insulation on external pipe runs.”
For households already on the fence about heat pumps, stories of unexplained performance drops are damaging. As Malyon put it: “This avoidable issue risks undermining confidence in heat pumps unnecessarily. When households experience higher bills or lower comfort, the heat pump itself is often blamed, but in many cases it is not the technology. It is the installation detail.”
WattsWatt has launched a free online tool at wattswatt.co.uk/tools/heatpumpcheck allowing heat pump owners to check whether their external pipework has been correctly insulated and to calculate their likely annual heat loss based on pipe length. Households that find problems are advised to contact their installer directly and request an upgrade. Where installers fail to act, the Consumer Rights Act 2015 applies, installations must be carried out with reasonable care and skill and be fit for purpose.
Professor Richard Fitton of the University of Salford’s Energy House Labs confirmed that research into the heat losses associated with inferior external pipe insulation is already under way.