Beyond the Surface: Rethinking Sustainable Construction

• This text was originally published in French in the Swiss newspapers Le Nouvelliste and La Côte. The present English version was generated through automated translation and has not been reviewed by the original publishers.

Sustainability buzzwords are everywhere in the construction industry today. But, as a scientist working on topic of C02 emission by construction, I am always wondering: How can we separate fact from fiction? Take, for example, the architectural trend of “green” structures covered with trees and vegetation. These buildings can be visually appealing and pleasant to live in, but claims of true sustainability need consider the extra materials needed to support the weight of plantings. The true carbon balance of construction is often counterintuitive, with much of the impact hiding in plain sight.

Embodied carbon

The carbon emissions due to production of construction materials (known as “embodied carbon”) account for approximately 10% of global emissions. In typical buildings, most of the embodied carbon comes from the structural elements: the foundations, walls, columns, and floors that allow the building to stand. Despite its relative importance, the influence of structural design on the carbon footprint of a building is rarely discussed.

Of course, the building with the lowest emissions is the one that does not need to be built. Reusing existing building stock is preferred for minimizing embodied carbon. However, the demand for new floorspace—both in Switzerland and, more significantly, at the global scale—means that construction will inevitably continue. We should ask ourselves, then, how we can build more intelligently.

There is no single “silver bullet.” It is tempting to search for a breakthrough material or technology that will revolutionize the construction industry overnight, but such a miracle cure is unlikely. Construction is shaped by long-standing practices, economic constraints, and the availability of materials at scale. No single innovation is likely to be deployed quickly enough, or broadly enough, to negate the sector’s emissions all at once. However, there is still considerable room for improvement within the material types and design approaches we already use.

From Concrete to… Design

For instance, consider the grey elephant in the room: concrete. It’s true that the production of cement is a large emitter of CO₂, but concrete is also the world’s most used building material. It is cheap and versatile, and offers high strength relative to its carbon footprint, making it quite efficient. Given the value chains already in place, improvements to the composition of concrete, such as the use of Limestone Calcined Clay Cement (LC³), have the potential to scale globally.

But material choice is only part of the story; more generally, we need to find ways to do more with less. The amount of material in our buildings is a consequence of design choices. Things like long spans, cantilevers, and irregular layouts all multiply the embodied carbon of a structure. Reducing floor spans from 7 m to 4 m, for example, results in thinner concrete slabs, yielding about 40% carbon savings. Irregular and showcase structures come at an elevated carbon cost; simplicity is best, and a return to regular, efficient structural systems can significantly lower the ecological footprint of a building.

Across scales

Ultimately, a multiscale approach is needed to activate levers for change at all scales: we can improve our materials (less CO₂ intensity), improve the efficiency of our structures (less materials), and prioritize longevity and reuse before new development (less construction). Switzerland, though small, can be a testing ground for such strategies and serve as a model for a kind of construction that is truly sustainable and not just green on the outside.