Circularity in construction is a beautiful concept, but devilishly difficult to realise. The first step must be a robust way of measuring it, otherwise we’ll drown in ‘circular-washing’
Earlier this summer, the Greater London Authority (GLA) published its draft London Plan for consultation, which strengthens the construction sector’s obligation to embrace circular economy principles.
The GLA wants to reduce London’s resource footprint and embodied carbon as part of the transition to net zero.
For the built environment, circular economy means using fewer raw materials, treating waste as a resource and considering how buildings can be more easily dismantled and adapted over their lifetime rather than demolished.
But while an inspiring ethos in theory, circular economy is science, not art, and a lack of an agreed industry-wide metric can make success difficult to measure.
You can’t improve what you can’t measure
Genuine application of circular economy principles requires thinking and acting holistically. Its principles must be embedded in a project and measured consistently.
Unlike embodied carbon, it’s far harder to measure the circularity of a building design because it relies on the integration of a whole set of design principles, including design for disassembly, designing out waste and designing for adaptability.
Without a common metric, it’s hard to set meaningful targets. The risk of “circular-washing” – making claims without robust evidence – grows.
Initial attempts
Some steps have been made toward a common metric. There are currently several indicators in use, but they’re not widely practised, and many fail to meaningfully capture the true objective of a circular economy.
One example is putting a number on the percentage of a building designed for disassembly. This seems simple and effective at first glance, but assessing it would involve reviewing every connection between each material and component in a building to determine whether it’s joined with mechanical, reversible connections or single-use welds, adhesives and sealants. That’s a laborious and costly exercise.
Other indicators measure waste produced, expressed as a percentage of waste diverted from landfill, but this only deals with the ‘end-of-pipe’ problem of waste, when the circular economy aims to eliminate waste by designing it out from the start.
These metrics also don’t address the other key part of the circular economy – cutting the demand for raw materials by reclaiming and reusing existing materials that have already been mined or quarried and processed into useful products.
What we think might work
Recently published research by Aecom for the GLA reviewed a longlist of circularity metrics and identified those most relevant to the built environment, assessing how effectively they measure circularity across design, construction and the building lifecycle.
This helped inform the evidence base for the next London Plan, because circular economy principles can’t take effect without planning policy.
We concluded that the Whole Building Circularity Indicator (WBCI) was the most comprehensive metric, covering resource circularity, flexibility, design for longevity and design for disassembly.
WBCI also produces a single composite score that indicates how linear or circular a building is and can draw on other robust metrics such as Flex 4.0 and Transformation Capacity. Crucially, it also addresses limitations found in earlier tools such as the Material Circularity Indicator.
That said, a single industry metric is not necessarily the only way to assess performance.
As building design and construction is multifaceted, it may make more sense to use two or three metrics to capture different aspects of circularity and provide separate measurements that can accurately capture trade-offs and integration.
Let’s get serious
Regardless of what is used, any new metric must be thoroughly tested and investigated, and it is difficult to set a target when there is no benchmark data to support it.
If any metrics are adopted as standard by industry, policymakers and industry bodies would need to provide guidance on their use, in the way that other common indicators do, such as NABERS UK in its Guide to Design for Performance and the RICS in its Whole life carbon assessment for the built environment.
With circular economy in buildings moving from a nascent aspiration to a practical requirement, now is the time for industry to come together and establish a consistent approach to measuring outcomes.
Agreeing on a common metric, or set of metrics, would enable more accurate and consistent measurement of success, providing a stronger evidence base for planning, designing and constructing projects with circular economy principles embedded from the outset.
This is a shared challenge, but it is one that the industry can address collectively.
David Cheshire is sustainability director at Aecom
