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Study into retrofits on London housing

London skyline

With London aiming for net zero by 2030, attention must turn to the housing stock, which contributes about a third of the city’s greenhouse gas emissions. Fagner Correia and Mauro Fazion took a deep dive into the impact of retrofits on emissions in the city.

Using the Energy Performance Certificate (EPC) dataset, the team identified that the average London family could save 9 MWh per year, with improvements like loft insulation and double glazing. This translates to an £800 per year saving on energy bills and a 1,700 kgCO2 reduction in emissions.

Below is the full paper from

The residential sector is responsible for approximately 20 percent of the world's energy-related greenhouse gas emissions. In order to improve this reality, it is essential to help and support the leading actor in this scene, the homeowner. In general, buildings are complex objects as each home may have very particular parameters: different materials (windows, walls, types of roofs, etc.), uses, and habits. No two cases are identical. In this paper, we addressed this problem by proposing a method to obtain estimates of energy and carbon savings resulting from a class of retrofit projects and housing profiles. We applied our formulas to conduct a case study of the London residential sector, supported by the publicly available Energy Performance Certificates (EPC) dataset. As a result of a multi-project renovation of a house, including loft insulation, double-glazed windows, and energy-efficient lighting (LED), we found that the average family in the Greater London area could save approximately 9 MWh in energy consumption, 1,700 kgCO2 in carbon emissions and more than GBP 800 on the energy bills, over a year, in contrast to a cost of around GBP 9,000 (or a return on investment of 11 years). In another example, applying the method to calculate what is needed to install heat pumps in each house in London, a total of GBP 16.9 billion would be spent, leading to savings of GBP 450 million per year (return on investment of 37 years). Finally, an overall upgrade to loft insulation would cost London households GBP 1.4 billion, generating GBP 290 million in annual savings (a 5-year return on investment).


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