Adopting the circular economy will be the most transformative change in the construction industry since the Industrial Revolution. That’s the bold statement I made when speaking at the Guildhall earlier this month at NLA’s Retrofit Summit. I encouraged the audience to consider retrofitting as an essential aspect of a ‘systems thinking’ approach that I believe we need to be taking in the built environment.

We are all custodians of the built environment. It’s crucial that the projects we work on leave a positive legacy for future generations – yet too often, we get caught in the silos of our respective specialisms, and the limits of our red line boundaries.

Holistic retrofit goes further than the physical building to acknowledge that the surrounding places and spaces between buildings are integral to creating resilient cities. Streets with limited biodiversity, excessive pollution, and poorly designed interaction between buildings and the public realm are common across UK cities. Addressing these issues requires retrofitting not only buildings but also the urban fabric itself, and its connectivity to places and communities.

A retrofitted future would see denser cities that make use of low-carbon vertical extensions, active ground levels that engage the public, greened facades, and public realms designed to promote healthy transportation and manage surface water more effectively. This vision – which I called a "Retrofit Utopia," reimagines the city as a place that is sustainable, livable, and resilient in the face of climate change.

The Grade II* listed Park Hill housing estate in Sheffield, a Civic Engineers project that was recently nominated for the Stirling Prize, saw a deep retrofit completed by stripping the building back to its concrete frame. This approach led to significant demolition and carbon loss, which informed the lighter touch of Phase 2, completed in 2022. By retaining more of the building’s existing structure, we were able to deliver a more cost-effective and lower-carbon solution.

I also discussed our work at 318 Oxford Street, the 1930s House of Fraser building where we conducted a detailed demolition audit to assess how structural elements could be repurposed, reusing 2.5 tonnes of steel within the building itself and donating a further 40 tonnes to another retrofit project, FORE Partnership’s TBC.London.

The Mayfield Depot in Manchester, a large-scale regeneration project that includes the city’s first new park in over a century, is another shining example of how engineers can lead the charge on creative reuse of a site’s historic infrastructure, hand-in-hand with the natural environment, as we did by daylighting the hidden River Medlock. This systems-thinking approach ties together landscape restoration, public realm improvement, and sustainable building practices.

Engineers are at the heart of the system thinking approach that is needed for retrofitting and reimagining our cities to be climate resilient for the future. A holistic approach is vital to meeting the industry's net zero ambitions, to create successful sustainable cities and enable people to lead happier and healthier lives.