Metabolic Architecture: Yale CEA Designs Living Systems That Could Out-Perform Conventional HVAC

A new study led by researchers at the Yale Center for Ecosystems and Architecture (Yale CEA), together with NYU, Purdue, YSE, Buro Happold and others, shows how plant-based biofilters could help reduce indoor CO₂ to levels below those found outdoors. Conventional HVAC systems cannot achieve this through ventilation alone, making this approach increasingly relevant as climate change drives higher CO₂ concentrations and greater demands on indoor environments.

Atmospheric CO₂ is rising each year and is projected to increase significantly over the next 50 years, from 420 ppm today to as much as 936 ppm. Growing evidence suggests that prolonged exposure to these higher concentrations may have serious negative health implications globally. This is particularly relevant in cities where people spend more than 90 percent of their time indoors, where CO₂ and other pollutants are already elevated. As outdoor CO₂ continues to rise, ventilation alone becomes less effective in reducing indoor CO₂. Because indoor concentrations are typically higher than outdoors, ventilation can bring them closer to outdoor levels, but it cannot reduce them below that baseline.

This new research investigates a complementary approach: building-integrated plant and microbial systems that use photosynthesis to remove CO₂ directly from indoor air. These systems could be designed to reduce indoor concentrations below outdoor levels, while simultaneously providing additional benefits, such as improving indoor microbial diversity. The researchers found that relatively simple design choices, particularly airflow and lighting design, can dramatically change how well these systems perform. These findings help explain why other studies in this field have sometimes been difficult to replicate, while providing a framework to inform future systems that are better optimized to improve indoor environments and human exposures. The findings will be presented at Photosynthetic Cities, a Yale CEA-convened program at AIA NYC on September 24 that brings together researchers, designers, policymakers, and practitioners to translate evidence on building-integrated vegetation and other living systems into actionable architectural and urban design strategies.

The project bought together an unusually interdisciplinary team, with expertise spanning across architecture, building-system design, air chemistry, civil and environmental engineering, plant and microbial ecology, exposure science, and computational and architectural modeling. The research was led and developed through Yale CEA in collaboration with co-authors from both academic and industry institutions.

Academic: Yale School of Architecture, Purdue University, NYU Tandon School of Engineering, Yale School of the Environment, Yale School of Engineering & Applied Science, Yale School of Public Health, and the Yale Institute for Biospheric Studies, Weill Cornell Medical School, Rensselaer Polytechnic Institute.

Industry: Buro Happold, SHoP Architects, Skidmore Owings and Merrill (SOM), Autodesk Research Residency Program (Boston).