Why a circular economy needs a different kind of maths
When we talk about reuse and retention in the built environment, the conversation often circles back to one thing: the numbers.
What’s the ROI? What’s the payback period? How does it compare to new build?
These numbers are largely reliant on simplified projections, while the reality more complex. Filled with unknowns, shifting system boundaries, and complex interdependencies that make reuse hard to model and even harder to value.
Hosted in partnership with Feilden Clegg Bradley Studios, our recent roundtable brought together developers, architects, engineers, surveyors, policy makers and funders to confront the real blockers to circularity. Yes, the usual policy and procurement, but also challenging our perspectives.
Because financial motives don’t always need to be the starting point, yet they often emerge as the most powerful deciding factor.
The parkrun principle
Take parkrun. A volunteer-led weekly 5k that began not with a financial goal, but with a social, human, and healing one. Yet a six-month study by Sheffield Hallam University found it now contributes £667 million annually to the UK economy, with significant returns in wellbeing and healthcare savings.
It worked because the system was designed for sustainability, not just in terms of resources, but relationships.
What if we treated building reuse the same way? Seeing the value of retention not just as what is embedded in a structure but as a system.
Examples within the built environment are abundant. The adaptive reuse of Shrewsbury Flaxmill Maltings avoided 900 tonnes of embodied carbon, supported over 550 jobs, and contributed to a 42% drop in local crime.
In Bristol, the Sparks Project is showing the transformative capacity of meanwhile spaces to not only fill vacant shop units but also lift community welfare and contribute to its socio-economic fabric.
We know that reuse reduces waste and emissions. That it protects heritage, character and community. That it avoids extraction and disruption. But we still struggle to integrate these benefits into the financial models that drive decision-making.
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“What if we treated building reuse the same way? Seeing the value of retention not just as what is embedded in a structure but as a system.”
At the roundtable, we asked:
– How can we generate and/or demonstrate the same returns when retrofitting and reusing?
– What research and collaboration are needed to achieve this?
– How do we account for benefits of retained fabric?
– How could socioeconomic benefits beyond the site boundary be linked to the retrofit itself to improve the project's or client’s overall financials?
What became clear is that current systems are too reductive. They prioritise immediate outputs over long-term outcomes, tangible costs over intangible gains, and overlook the interdependencies between buildings and people, places and policies.
Yes, this is a blocker. But the roundtable attendees also saw it as an opportunity to rethink, reframe and respond.
Key outcomes
To make the case for reuse, we need consistent, system-wide measurement that captures its full impact, from financial and environmental to social, community and heritage. These often-overlooked factors are interconnected and influence everyone from investors to policymakers. When we show how benefits in one area create gains in another, broader support for reuse will follow.
From scanning and modelling to lifecycle tracking, digitisation helps surface and quantify hidden benefits. Making them usable in planning, procurement and policy contexts.
Most financial models are built on short payback windows. But the real benefits of reuse – from embodied carbon savings to healthier, more cohesive communities – often reveal themselves over decades. If we want long-term gains, we need long-term thinking.
Reuse still carries perceived risks, but better briefing, procurement models and ownership structures can reduce uncertainty and unlock opportunity.
We can’t retrofit with spreadsheets alone. We need hands-on expertise from a workforce skilled in heritage construction, adaptive reuse, and low-carbon techniques.
Too often, historic buildings are seen as a constraint. But they play a key role in place making and social economic value retention. Done right, reuse breathing new life into these assets and unlocking value that goes beyond aesthetics.
From job creation to tax reform, we need to improve how we communicate the economic benefits of reuse. Policy tools like VAT reform, carbon taxes, and financial rebates can help — if backed by solid evidence.
What's next?
Change is possible. Not by tearing down systems entirely, but by adjusting what we value within them. Next, we’re taking the roundtable insights forward to explore how we can unlock the full potential of reuse. Not by completely abandoning financial logic but expanding it.
If you’re exploring circularity in your projects, working on innovative valuation methods, or simply want to be part of the shift, please get in touch.
The roundtable was co-chaired by Ian Poole (Elliott Wood) and Tim den Dekker (Feilden Clegg Bradley Studios), with outcomes summarised from a rich discussion contributed to and by the following participants and organisations:
Matt Bullivant (Athora), Tom Bunn (Elliott Wood), Sam Carlsson (Derwent), Ben Cross (More), Paul Ekins (UCL), Kell Jones (UCL), Geoff Rich (Feilden Clegg Bradley Studios), Ben Stallwood (Aviva Investors), Yemi Usman (Turner & Townsend), Zoe Watson (Bioregional), Sara Williams Willard (Workable City), and Joe Jack Williams (Bywater).
