Climate and construction: the circular building economy envisages life beyond the grave

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Forces are converging in the global construction industry that cannot be ignored.

At the top of the list, buildings are expected to be designed to emit less carbon emissions from heating and cooling operations and have lower energy requirements for lighting and ventilation. Increasing attention is also being paid to the carbons associated with the construction process itself, resulting in more off-site manufacturing and faster on-site assembly.

The construction materials themselves also come under scrutiny. US President Joe Biden’s “Buy Clean” is not a better example. announcement made last December.

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

Therefore, life-long or “cradle-to-grave” carbon assessments are becoming increasingly important.

Today’s buildings are expected to have a useful life of at least 50 years. Of course, this varies depending on the potential for reassignment and upgrading over time and changing occupancy demands.

However, what happens once that useful life is over and the building is threatened with demolition? Recycling seems the obvious answer.

Ironically, one of the basic building materials associated with high carbon intensity during its initial manufacture also has the best recycling record. We are talking about steel.

For example, the Institute of Reinforcing Steel for Concrete claims that nearly 100% of the steel used in reinforced concrete was made from other metal products. In addition, 65% of all steel rebar is recycled again.

Concrete, another fundamental but highly carbon-intensive material, is also showing an increasing recycling rate.

the Building Materials Recycling Association estimates that around 140 million tonnes of concrete are recycled into usable aggregates every year. This represents approximately 5.5% of the total aggregates market.

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

Overall, wood accounts for 20-30% of construction and demolition waste and accounts for 10% of all materials deposited in landfills each year, emitting GHGs as it decomposes.

A study 2021 conducted by UBC sustainability researcher Jacob Forrest confirms this.

“In the construction and demolition sector, wood is the main component of landfill waste. »

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

The increased attention paid to the fate of end-of-life building materials has given rise to the term “circular construction economy”. It is the concept of reusing and repurposing materials as opposed to recycling.

In a recent webinar, Jennifer Schooling from the University of Cambridge in the UK explained that the circular building economy means looking beyond the “grave”, i.e. doing better than simply to recycle. It’s about reusing disassembled components in another project decades later.

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

Carson spoke of buildings that are actually designed to consider the potential for dismantling and repurposing at the end of a building’s useful life, rather than just demolition. Selecting materials and components that can be fully reused would divert them from the landfill, thus avoiding the recycling process.

This requires acute awareness at the initial design stage, Liebetanz explained. Additionally, including dismantling and repurposing goals in the project design brief also requires bringing owners and contractors into conversation early, to maximize commitment and flexibility.

The rapid increase in material costs over the past year, estimated at 20% overall in North America, will bring more attention to the repurposing and reuse of materials. Increased global carbon awareness and higher carbon taxes will be further motivating factors.

However, Schooling believes that new thinking about the entire infrastructure of the construction process must first be developed.

“We just have to reconfigure our mentalities. Just because we haven’t done certain things in 30 or 40 years doesn’t mean we shouldn’t.

John Bleasby is a freelance writer based in Coldwater, Ontario. Send your comments and story ideas on climate and construction to [email protected]

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