What about costs though? How do the numbers stack up? The first thing to say on this is that the rules of the game are changing. An increasing focus on whole-life carbon assessment, (which accounts for both operational and embodied carbon), will make it essential for designs to reduce consumption, reuse as much material as possible and specify low-carbon options for the remainder. Robust guidance in London and The City of London (alongside emerging guidance from cities such as Leeds and Manchester) require whole life carbon assessments. Further progress needs to occur with Part Z (a proposed amendment to Building Regulations) supported by WSP and other esteemed bodies including RICs, RIBA, IStructE, CIBSE, LETI and UKGBC the time for nationwide change is surely close.

It's also something the market is demanding, so early adopters can secure a competitive advantage. As our report Beyond the Business Case, for the World Green Building Council highlighted, greener commercial buildings already command a premium on their leases, and spend less time empty between tenants. As investors, employees and customers pay closer and closer attention to these issues, the industry cannot afford to ignore the fact that US$130 trillion of investment globally is focussed on net zero and other environment, social and governance (ESG) areas. This figure equates to circa 40% of global investment and is commonly viewed as a tipping point. 

The progress made on reusing structural steel was driven by circular economy principles and points the way forward. WSP leads research and pilot schemes in this area, so I’ve seen the impressive results first-hand. Not only did we find that reuse can drastically cut embodied carbon compared to using new steel, the huge price difference per tonne between scrap steel (£300) and new steel (£1,200) noted in 2022 leaves plenty of margin for deconstructing, sorting, testing and making the steel suitable for reuse as structural steel in buildings. 

There’s no reason why similarly impressive progress couldn’t be made with reusing other materials. For example, precast concrete planks would be a good candidate if the industry can develop design guidance that details how and where they can be reused. At the same time, low-carbon materials such as hempcrete also deserve to be taken more seriously by the industry.

Hempcrete is made by mixing hemp shiv (the woody stem of the hemp plant) with lime or another binder. Because hemp plants absorb double the CO2 of the average commercial forest (circa 11 tonnes per hectare) as they grow, hempcrete locks away more carbon than it takes to produce. Hemp also integrates naturally into crop rotation cycles and doesn’t require pesticides or herbicides. It is therefore a perfect complementary crop to grow alongside food production in a highly sustainable manor, with significant circular economy principles as it is locally sourced and supports the wider community. What’s more, hempcrete walls have better thermal performance than conventional construction whilst also allowing the building to breath naturally which leads to enhanced internal air quality.  

Back in 2015, WSP designed the world’s largest monolithic hempcrete wall as part of the BREEAM Outstanding Bright Building at the University of Bradford in response to the circular economy whilst greatly enhancing the internal thermal performance and occupant well-being whilst lowering the embodied carbon of the building. 

Professor Amir Sharif, Dean of the Faculty of Management, Law and Social Sciences, notes: “We have been teaching and researching in the area of Circular Economy for several years. Our recognition for delivering responsible management education, as well as working with colleagues in engineering and life sciences on the application of regenerative materials, highlight we are committed to applying cutting edge approaches to making the world a better place.” The university is also leading on research into biopolymers, as well as sustainable construction including “green”, glass-based concrete which contributes to net zero construction through both lighter as well as lower carbon-intensive materials. 

“The Bright Building continues to be one of the most energy efficient buildings on our campus and is contributing directly to our strategy of becoming a net zero campus.”, notes Professor Sharif. 

WSP has also recently worked with Greencore Construction whose homes use hemp-lime panels as part of a modern methods of construction (MMC) design that is carbon negative for whole life carbon. 

Time for action

It’s clear that the conventional approach to building design and construction has to change in response to environmental degradation and whole life carbon drivers. It’s also increasingly clear, in the face of the climate crisis and shifting market forces, that it’s an approach which needs to change sooner rather than later. It’s in everyone’s interests to embrace material reuse and adopt innovative low-carbon materials.

Find out how these principles are being used on current projects

As technical partners, WSP was involved in The World Green Building Council’s Circular Built Environment Playbook – a critical guide for the construction sector to accelerate the adoption of circular economy and resource efficiency principles.

This report presents strategies for the built environment to reduce its resource consumption and to help achieve global climate targets. It contains numerous solutions, including four of our own case studies:

• Elephant and Castle Town Centre, London, UK – delivering steel’s full reuse potential (page 35)
• The Recycled Houses, Denmark – report looking at whether recycled materials are as good as new materials (page 35)
• Centre Block Rehabilitation, Ottawa – Canada’s large heritage rehabilitation project (page 48)
• Arden Precinct, Melbourne, Australia – circular economy embedded into masterplanning and building design (page 71)