Our buildings and energy research has looked at how to shift the UK built stock to net-zero by 2050 in the most cost effective, resilient, acceptable and practical way, maximising co-benefits and minimising unintended consequences. There is a significant resource of untapped energy-saving opportunities in UK homes, with technical potential exceeding 50% and a cost-effective potential exceeding 25% by 2035. We have found that the majority of the long-term energy saving comes from moving to high-efficiency heating systems (like heat pumps), rather than from insulation.
Heat pumps are the key decarbonising technology for buildings
Decarbonising energy use in buildings will rely on the deployment of heat pumps. However, there are policy, technical, public acceptance and cost challenges to be overcome to achieve roll out at the level and speed required to meet net-zero goals. Successful building retrofit and renovation for energy efficiency requires attention to be paid to timings, bespoke/building-specific requirements, and complementary objectives, i.e. more than just carbon reduction.
Getting heat pumps to work as efficiently as possible is one of the greatest opportunities and challenges to UK decarbonisation. During cold weather, improving the efficiency of heat pumps from average to good efficiency could save as much energy as insulating all UK solid walls. Heat pumps could be used flexibly to help manage peak electricity demand, but more standardisation of the heat pump stock would be required.
Heat pumps powered by renewable electricity challenge the ‘fabric first’ approach. With offshore wind and PV costs reducing, and with heat pumps needing only a quarter of the energy of gas boilers, it is becoming cheaper to generate decarbonised heat than to save it. This may limit the need for ‘deep’ retrofit, with insulation prioritised where it is particularly cheap (e.g. during normal refurbishment/extension) or where it is essential for health and comfort and for the efficient operation of heat pumps.
Hybrid appliances which combine a gas boiler with a heat pump could be a low disruption, low-cost pathway to net-zero, reducing energy demand by 60% (compared to current gas boilers), and also reducing peak electrical demand by 10 GW (compared to air source heat pumps).
Health impacts of energy efficient homes can be considerable
Energy efficiency can result in considerable health benefits, particularly for vulnerable people. A substantial number of UK homes experience temperatures that are judged as too low for the health of the vulnerable. Older dwellings, detached homes, single occupancy and living in the North of England are all associated with the lowest share of hours at the recommended temperature threshold in the bedroom, living room, and hallway.
However, greater attention is needed to avoid unintended health consequences, such as installing measures that impact ventilation in regions with high levels of radon.
Performance gaps can be addressed
Data, its analysis and visualisation from monitored buildings during construction and in occupation can help UK buildings transition to net-zero. Much of the data is already being collected or can now be collected at minimal cost. It is now practical and cost effective to use thermal cameras on-site to identify building defects during construction and therefore help to reduce the performance gap.
Energy Performance Certificates must be improved
Energy Performance Certificates (EPCs) are a key policy tool and their usefulness can be considerably enhanced by linking them with data about actual energy use in buildings. In particular, this could be of use in the non-domestic buildings sector.
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