Dalkia has successfully completed a £3.1 million decarbonisation of the electrical and mechanical systems at Arup’s London headquarters, 8 Fitzroy Street. The project involved transitioning the building’s core services away from gas to high-efficiency electric heat pumps, all while the office remained fully operational.
Delivered with Arup as the designer and Dalkia as the Principal Contractor, this initiative serves as a potential model for retrofitting low-carbon heating and cooling systems in large commercial buildings without disrupting their usage. This is a critical concern for facilities managers, building services engineers, and electrical contractors operating in the constraints of city-centre offices.
The project marks a significant step in Arup’s Net Zero Plan, which aims to make the consultancy a science-based net zero organisation by 2040 across its global properties. At 8 Fitzroy Street, the decarbonisation involved replacing two existing gas boilers and two chillers with air-source heat pumps using R513A refrigerant. These upgrades result in heating and cooling efficiencies of 300 to 400%, compared to the previous gas boiler system’s 85%, with R513A’s global warming potential being 56% lower than the R134a refrigerant it replaces.
Additionally, domestic hot water generation has been electrified by replacing gas-fired water heaters with four CO2-based heat pumps, further reducing on-site fossil fuel use. These upgrades are expected to reduce annual carbon emissions by approximately 250 tonnes of CO2, equivalent to the yearly emissions of more than 150 average UK homes, directly supporting Arup’s science-based emissions reduction targets.
While the building remained in use, the project required careful planning to sequence activities around daily office operations, ensuring minimal disruption to power and building services. Dalkia and Arup adopted out-of-hours work schedules, used prefabricated pipework, and coordinated trades to reduce on-site time, highlighting the practical challenges of electrifying heat in a live commercial environment.
Glyn Fells from Dalkia remarked, “This project demonstrates the achievements possible when design innovation and expert engineering come together. 8 Fitzroy Street exemplifies practical decarbonisation, reducing operational carbon while maintaining comfort in a fully occupied building.”
Stephanie Welch, London Office Leader and Head of WFM at Arup, added, “8 Fitzroy Street is not just Arup’s headquarters; it reflects our Net Zero Plan in action. By decarbonising our own estate, we demonstrate our commitment to science-based targets and lead by example in transitioning to a low-carbon future. This retrofit is a tangible step towards our goal of becoming a net zero organisation by 2040, applying our sustainability principles to the buildings we design, own, and occupy.”
The 8 Fitzroy Street decarbonisation scheme signals a trend of large commercial offices moving from fossil fuel systems to high-efficiency electric alternatives, particularly where owners have formal net zero commitments. The combination of air-source and CO2-based heat pumps, lower global warming potential refrigerants, and a retrofit methodology suitable for occupied sites offers a practical approach to reducing operational carbon in similar buildings. As more clients opt to decarbonise existing properties rather than rebuild, projects like this are expected to become increasingly prevalent for electrical contractors, consultants, and facilities management teams within the UK’s commercial property sector.
