Applying the circular economy to the construction sector?

Proportionally, the construction of new buildings will soon pollute more than their operation. Moreover, the potential to recycle a building’s “waste” material post-demolition is still underexploited. So what if a building’s structures and systems were designed to be reused several times over centuries?

The past decade has seen efforts directed primarily at reducing the operational energy consumption of buildings (heating, lighting, etc.). In the near future, construction and demolition will comparatively account for more carbon emissions. Waste products from these two phases abound, because buildings are not designed to be recycled. Even if anything can be recycled in theory, it always comes at an economic and ecological cost. Furthermore, recycling often leads to a loss in quality in terms of material properties, potentially disqualifying recycled construction materials from being reused for their initial use. Recycling is not a miracle solution.

Opposing the linear economy
The prevailing model in the construction industry (based on the predominant linear economic model of production-consumption-disposal) strongly contributes to depleting natural resources. “To make concrete, you need sand. Today, we have to scrape the seabed 200 meters underwater, destroying any existing flora and fauna in the process, because we have used up available sand resources. Desert sand is too smooth to be used in construction because of wind erosion,” explains
Corentin Fivet, EPFL professor and director of the Structural Xploration Lab based at the smart living lab. That is why it has become urgent to look for other models that, essentially, increase the lifetime of extracted raw material and of the components produced with it. The circular economy stands in opposition to the linear consumption economy. “The idea is to close the loop for materials according to the principle of ‘nothing is lost, nothing is created, everything is transformed or transferred.’ Reducing the amount of material used, repairing, reusing, recycling, and returning to nature, are principles that can be applied in that order of priority: repairing consumes less energy than reusing, which consumes less than recycling, and so on…”

Multiple lives for a building’s structures and systems
Understanding how to design a building’s support structure (walls, slabs, columns, flooring, roofs, foundations) in a way that makes them reusable over several generations of buildings is one of the goals of the Structural Xploration Lab. Using locally sourced materials to reduce transportation costs and associated carbon emissions is also part of the philosophy. A building’s lifespan is typically around 100 years, so reusing elements over multiple centuries would involve adopting a very long-term perspective – nothing short of a paradigm change.
To look that far into the future, the team developed tools to evaluate the potential of materials from demolished buildings to be reused. “Considering the Swiss building stock, we have no idea what percentage of materials or components could be reused post-demolition. Being able to reuse demolished heritage to build new buildings is one of the scenarios that we will have to investigate,” says Fivet. It isn’t enough to reuse structural systems only, he explains, instead, all the integrated systems from the old buildings (plumbing, insulation, air and waterproofing, and a building’s finishes) should be reused, and that despite having to disassemble and reassemble them.

Circular economy or restitution to nature
As things stand, the researchers still have to find out whether the circular model (reusing elements over centuries) could be successfully applied to the construction industry, or whether elements should simply be returned to nature once a building is demolished. “How can we measure reuse? What technologies would promote reuse? These are questions we expect to address over the coming years,” concludes Corentin Fivet.

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