Buildings reimagined as a climate solution

At COP26, the 2021 UN Climate Change Conference in Glasgow, SOM unveiled Urban Sequoia—a concept for buildings and their urban context to absorb carbon at an unprecedented rate. SOM has developed the first step toward achieving this goal on a broad scale, with a prototype for a high-rise building that can be built today.

The need to transform the built environment is clear. The building sector generates nearly 40 percent of all global carbon emissions. As urban populations continue to grow in the coming decades, studies have predicted that another 230 billion square meters of new building stock will be needed by 2060.

The central proposition of Urban Sequoia is that the built environment can absorb carbon. SOM’s proposal transforms buildings into solutions—radically rethinking how buildings and cities are designed and constructed. It is a viable approach that could have a far-reaching impact, with the potential to create a circular economy that absorbs carbon.

“Urban Sequoia is a systems approach, a philosophy,” says SOM Sustainability Director Mina Hasman. “It is a way of thinking about cities as ecologies, as living and breathing systems that can be reconfigured to achieve dramatic reductions in whole life carbon, reframing the built environment as a solution for the climate crisis.”

Designing a buildable prototype

Urban Sequoia brings together different strands of sustainable design thinking, the latest innovations, and emerging technologies and applies them at the scale of a building. By holistically optimizing building design, minimizing materials, integrating biomaterials, advanced biomass, and carbon capture technologies, Urban Sequoia achieves substantially more carbon reductions than what has been possible by applying these techniques separately.

Since unveiling Urban Sequoia at COP26, SOM has refined the architecture of the high-rise prototype, and presented the next phase of the design at COP27 in Sharm El-Sheikh, Egypt in 2022. Three questions guided the process: how low can we go in emitting carbon in construction, how high can we go in carbon sequestration, and how long can we go in extending the typical building’s lifespan?

The latest design for Urban Sequoia answers these questions. The building would reduce upfront embodied carbon by 70 percent—from construction alone—when compared to that of a typical high-rise. In the first five years of the tower’s life, the building would reach a 100 percent reduction in whole life carbon, achieving net zero. Over an extended, 100-year lifespan, an Urban Sequoia building would absorb more than 300 percent of the amount of carbon emitted in its construction and operation. 

Beyond net zero: Toward a carbon-removal economy

The nature-based strategies behind the high-rise can be applied to buildings of all sizes and types. Each building type uses carbon-sequestering materials, like timber and bio-concrete, to reduce embodied carbon emissions, and advanced technologies such as energy-generating solar glass to lower operational carbon emissions.

This solution allows us to move beyond net zero to deliver carbon-absorbing buildings, increasing the amount of carbon removed from the atmosphere over time. The captured carbon can then be put to use in various industrial applications, completing the carbon cycle and forming the basis of a new carbon-removal economy. With integrated biomass and algae, the facades could turn the building into a biofuel source that powers heating systems, cars, and airplanes; and a bioprotein source usable in many industries.

Beyond the building: Making cities part of the solution

On an even broader scale, the byproducts of building an Urban Sequoia will help revolutionize the way we design and maintain infrastructure. Captured carbon and biomass can be used to produce biomaterials for roads, pavement, and pipes. By converting urban hardscapes into gardens, designing intense carbon-absorbing landscapes, and retrofitting streets with additional carbon-capturing technology, former grey infrastructure can sequester up to 120 tons of carbon per square kilometer. When replicating these strategies in parks and other green spaces, we can save up to 300 tons per square kilometer of carbon annually.

If every city around the world applied this concept, the built environment could remove up to 1.6 billion tons of carbon from the atmosphere every year. Bringing this idea from concept to reality will create a network of Urban Sequoia buildings across the world that absorb carbon, every year, for the next 100 years or more.

“The power of this idea is how achievable it is,” says Yasemin Kologlu, Design Principal. “Our proposal brings together new design ideas with nature-based solutions, emerging and current carbon absorption technologies and integrates them in ways not done before in the built environment.”