Toward Carbon-Negative Architecture

Their goal is to find the most efficient geometries that will minimize the amount of needed material—reducing embodied carbon and construction waste. In addition, the team is exploring the ideal shapes for the columns, beams, and slabs that can create a thermal mass to passively heat and cool the interiors. In the process, they are creating geometries with very great surface areas that can help absorb more carbon from the air while creating more temperature regulation and eliminating the need for constant energy use to condition the building.

Shu Yang, the Chair of Materials Science and Engineering Department at Penn Engineering is developing a carbon-absorbing and storage concrete. Yang’s new recipe will scrub carbon from the air as well as capture it in the manufacturing process. The team is looking to develop a new mix that partially replaces cement for optimal carbon reduction benefits as well as thermal properties. The project is an extension of Yang’s work in biophilic design and engineering, looking to nature for solutions that are more effective and less energy intensive, including a material that can pull water from the air.      

To allow for minimized material use and maximized surface area, the team is developing concrete prototypes of the new recipe, along with various design schemes. The efficient 3D-printing assembly and post-tensioning technologies reduce the amount of construction materials required and waste produced. The optimized, self-supporting designs are generated with minimal start and stops.

Dorit Aviv, also a faculty member at the Department of Architecture, leads the Thermal Architecture Lab (TAL), where she and a team of students are exploring passive heating and cooling design strategies that will reduce operational energy usage. They are working to understand how the concrete slab prototypes designed by the PSL can act as a thermal mass to provide comfortable indoor temperatures when combined with natural ventilation. The increased surface area of the printed concrete not only helps sequester more carbon from the atmosphere, but it augments the absorption and release of heat as well, making the slab more effective as thermal mass.

“For architecture to really deal with climate change, we have to address the overheating of our buildings and cities and at the same time reduce energy usage in buildings,” Aviv says. “We are looking for ways to innovate in that space through design, so that we can rely less on mechanical heating and cooling.”

The TAL team tests room-scale slab mockups inside a special climate chamber. As the printed concrete cures, they place sensors inside that indicate the internal temperature within the slab and they use computational fluid dynamics and energy modeling to predict the performance of different slab designs and suggest improvements.

For students, the project has them put their research into practice under real-world conditions such as deadlines and quarterly report reviews. It also allows them to see the whole design process, beyond simply designing something and sending it off. “Sometimes we don't really see the results from what we design as a physical prototype,” says Hua Chai, a PhD in architecture student who works with Akbarzadeh at the PSL. “On this project, we are involved in everything from design to fabrication from beginning to the end. It's allowed us to investigate and optimize the process to make our workflows better.” Zherui Wang, another PhD student in architecture, appreciates the opportunity to pursue his dual interest in thermal and structural performance by working on the project with Aviv at the TAL. “The collaboration across labs also enables us to test our research assumptions through full-scale experiments and prototypes," says Wang.

An early version of the 3D-printed carbon absorbing concrete was first shown to the public in 2023 as Diamanti, a large-scale prototype in Venice, Italy at Palazzo Bembo as part of the Time-Space-Existence exhibition during the Venice Architecture Biennale. (Diamanti is Italian for Diamonds, which is the fundamental geometry of the systems). Ultimately, Akbarzadeh is aiming to bring these innovations to the construction market as prefabricated, 3D-printed beams, and ribbed floor arches. And his lab’s work isn’t limited to re-imagining concrete. The PSL is also developing the use of glass as a novel lightweight construction material to optimize performance and increase structural spans. In November, Akbarzadeh and his team will unveil a prototype at the Corning Museum of Glass in New York.

“Both our concrete and glass work take inspiration from nature to optimize structure and reduce material use,” Akbarzadeh said. “In fact, the glass research can be applied to any sheet-based material like wood or even steel plates, proving that challenging materials can be made efficient and beautiful.”