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Climate and Construction: Circular building economy contemplates life beyond the grave

John Bleasby
Climate and Construction: Circular building economy contemplates life beyond the grave

Forces are converging on the global building industry that cannot be ignored.

At the top of the list are expectations that buildings will be designed to emit less carbon emissions from heating and cooling operations and have lower energy demands for lighting and ventilation. Growing attention is also being paid to the carbons associated with the construction process itself, resulting in more offsite fabrication and quicker onsite assembly.

Building materials themselves are also coming under scrutiny. No better example is U.S. President Joe Biden’s “Buy Clean” announcement made last December.

“In 2022, the General Services Administration (GSA) will require contractors to disclose the embodied carbon of building materials for new building and major modernization contracts.”

As a result, whole life or “cradle-to-grave” assessments of carbon are becoming increasingly important.

Buildings today are projected to have a useful life of at least 50 years. Of course, this varies based on the potential for repurposing and upgrading as time goes by and as occupancy demands change.

However, what happens after that useful life is over and the building faces demolition? Recycling seems the obvious answer.

Ironically, one of the basic construction materials associated with a high level of carbon-intensity during its initial fabrication also has the best record for recycling. We’re talking about steel.

For example, the Concrete Reinforcing Steel Institute says almost 100 per cent of the steel used in reinforced concrete has been fabricated from other metal products. Furthermore, 65 per cent of all reinforcing steel bars are recycled yet again.

Concrete, another fundamental yet carbon-intensive material, is also showing a growing rate of recycling.

The Construction Materials Recycling Association estimates about 140 million tons of concrete is recycled annually into usable aggregates. This represents roughly 5.5 per cent of the total aggregates market.

While concrete’s recycling rate might appear low compared to steel, wood doesn’t fare much better.

Overall, wood represents 20 to 30 per cent of construction and demolition waste, and accounts for 10 per cent of all materials deposited in landfills each year, emitting GHGs as it decays.

A 2021 study conducted by UBC Sustainability scholar Jacob Forrest confirms this.

“Within the construction and demolition sector, wood is the largest component of waste going to disposal.”

He adds, “Recycling options for lumber and engineered wood that cannot be reused are limited.”

The increased attention being paid to the end-of-life fate of construction materials has spawned the term “circular building economy.” It’s the concept of reuse and repurposing of materials as opposed to recycling.

During a recent webinar, Jennifer Schooling of the University of Cambridge in the U.K. explained the circular building economy means looking beyond the “grave,” that is to say, doing better than just recycling. It’s about reusing disassembled components in another project decades later.

Tim Carson of Westgate Construction based in Romsey, U.K., and Kai Liebetanz of the UK Green Building Council continued this thought.

Carson spoke of buildings that are actually designed to take into account the potential for disassembly and repurposing at the end of a building’s useful life, rather than simple demolition. Selecting materials and components that can be wholly repurposed would divert them away from the dump, avoiding the recycling process.

This requires acute awareness at the initial design stage, explained Liebetanz. Furthermore, including disassembly and repurposing objectives in the project’s design brief also requires bringing owners and contractors into discussions early, in order to maximize engagement and flexibility.

The rapid increase in material costs over the past year estimated at 20 per cent overall in North America will bring more attention to material repurposing and reuse. Increased overall carbon awareness and higher carbon taxes will be other motivating factors.

However, Schooling believes new thinking surrounding the entire building process infrastructure must first be developed.

“We simply need to reconfigure our mindsets. Just because we haven’t been doing certain things for the past 30 or 40 years doesn’t mean we shouldn’t.”

John Bleasby is a Coldwater, Ont.-based freelance writer. Send comments and Climate and Construction column ideas to


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