Jack Brunton and Ioana Price of AECOM explore how designers can redefine carbon calculations by assessing carbon at the early design and optioneering stage.
The built environment is a significant contributor to the UK’s carbon emission and is responsible for almost 25% of the UK’s total greenhouse gas emissions. Within that footprint, a significant share lies in embodied carbon – the emissions associated with materials extraction, manufacturing and construction that are locked into a building before it’s ever occupied.
It’s no secret that decarbonisation remains at the top of the sector’s agenda given the critical role we’ll play in helping to achieve the UK’s net zero targets. Progress is being made, but not at the pace we need. Between 2018 and 2022, emissions from the UK built environment fell by 13%. That sounds promising – until you realise we needed a 19% drop in the same period to stay on course for net zero.
That shortfall of 6%, or 11 million tonnes of CO2 equivalent, is roughly the same as the total annual emissions of 6.5 million cars.
We need to innovate our approach if we’re to bridge this gap.
Early-stage optioneering: a different approach
Traditionally, structural carbon calculations are carried out at the end of RIBA Stage 2. By this point, the massing is often fixed, materials are broadly decided on and carbon is something we try to reduce at the margins. That’s not good enough.
The decisions that make the biggest impact on carbon – decisions about structural frame typologies, material types, building form and geometry – are made far earlier, typically during RIBA Stages 0 and 1.
At that stage the design is still fluid. Key decisions about structure, layout, and materials haven’t been locked in yet, so there’s still flexibility to explore low-carbon options without adding time or cost. However, structural engineers are rarely involved in detail at that point, and carbon calculations are often seen as too slow or too expensive to be viable.
Fortunately, tools are being developed to make carbon calculations simpler to embed in the earliest stages and avoid costly retrofits.
For example, at AECOM, we’ve developed Eco.Zero – the industry’s revolutionary conceptual design tool that allows structural engineers to carry out rapid carbon and cost comparisons for a range of structural frame options, tailored to a project’s specific use, geometry and ground conditions. The idea is simple: empower the design team to make informed, low-carbon choices from day one, and do it without adding delay or cost.
At its core, Eco.Zero is a suite of digital tools built to support AECOM’s structural engineers in the earliest stages of design. It was developed in-house by our multidisciplinary team – structural and geotechnical engineers, sustainability specialists and cost managers – to allow for instant optioneering across 11 structural typologies. You can toggle parameters like building height, number of storeys, basement inclusion and structural material to explore how each impacts both embodied carbon and cost.
A tool designed by engineers, for engineers
Crucially, Eco.Zero’s not just a calculator – it’s a design tool. Other tools might offer carbon data, but no others include full foundation design, real cost data and the ability to iterate structural solutions in seconds rather than weeks.
That means architects, clients and engineers can sit around a table and discuss carbon and cost implications right from the outset. And crucially, they can do it with robust data in hand. It makes conversations more collaborative, less hypothetical and more productive.
The traditional process might see a structural engineer take a couple of weeks to develop viable options, followed by reviews with quantity surveyors and sustainability consultants. That’s a lot of time spent before you even start making meaningful comparisons. The tool supports a variety of uses – from residential to healthcare, commercial to education.
A case study in impact
Designs for the new Queen Mary School of Business and Management in Mile End, London offers a unique case study for the impact of Eco.Zero. The scheme for a new seven-storey campus building had previously progressed to RIBA Stage 4 before being paused. But when the project restarted in 2021, we had the opportunity to re-evaluate the structural design from a carbon perspective using Eco.Zero as an integral part of that process.
Using the earlier design as a baseline, we assessed 11 structural frame typologies with Eco.Zero to identify the most efficient solution in terms of embodied carbon, buildability and performance. We worked closely with the architect and facade engineer to optimise column grids and layouts, while early engagement with the wider design team helped ensure that decarbonisation was embedded from the outset of the project.
Combined with improvements to the structural frame and foundations, targeted material specification, and close coordination with the contractor’s piling specialists, the tool helped deliver a 35% reduction in embodied carbon compared to the original scheme.
This project has since been presented at AECOM’s global technical academy and continues to support our wider learning on how to embed decarbonisation into structural design workflows from the outset.
A platform for change
The construction industry has long worked within tight margins – for time, cost and carbon. With growing pressure to deliver on net zero, we need tools that enable faster, smarter decisions without compromising design quality or delivery timelines.
Tools like Eco.Zero aren’t a silver bullet, and won’t solve embodied carbon on their own. But it’s one example of how we can rethink our approach – how we can bring structural engineering, sustainability and cost management together at the moment it matters most: the beginning.
Jack Brunton is structural sustainability lead & Ioana Price is deputy structural sustainability lead at AECOM