courtesy Michael/Adobe Stock

Air quality has become a matter of elevated importance in recent years. Discoveries about the enhanced spread of COVID-19 in poorly ventilated spaces have raised awareness about the health risks of inadequate air circulation and filtration indoors. Meanwhile, the ability to connect with the natural world has taken on new significance with regard to improving and maintaining physical and mental health.

Architects and designers are increasingly looking to living systems to help improve indoor air quality and general well-being. Studies indicating the ability of indoor vegetation to diminish the presence of ultra-fine pollutants have made plants a more attractive enhancement to interior environments. Although some critics caution against the potential increases in plant-induced mold growth and allergic reactions, proponents advocate solutions to such problems, including appropriate species selection and adequate maintenance.

An alternative to individual plants, living walls have become popular ways to achieve a more significant functional and visual impact with indoor foliage. The positive findings in reports like Gensler’s “Why Walls Should Live” (2017) assessment, which found that living walls can improve air quality significantly, have encouraged this trend. The growing interest has spurred the development of interior landscape firms such as Wyomissing, Pa.–based Ambius, which offers consulting services to ensure optimal indoor environmental quality.

Studies indicating the ability of indoor vegetation to diminish the presence of ultra-fine pollutants have made plants a more attractive enhancement to interior environments.

As vertical foliage systems become more expansive in design scope, designers and manufacturers are devising other compelling ways to maximize performance while streamlining operations. Fresh Air Building Systems, a fabrication consortium with partners based in New York and North Carolina, for instance, aims to reforest cities from within. The founding members, who developed the Active Modular Phytoremediation System in a collaboration between Rensselaer Polytechnic Institute in Troy, N.Y., and Skidmore, Owings & Merrill, are working on the next iteration of the plant-powered air-purification wall. Unlike traditional HVAC filtration, which aims to sanitize by removing all microorganisms, the modules clean the air probiotically. Boston ferns, pothos, English ivy, and other remediating plants remove toxins and pathogens while diffusing healthy microbes into indoor spaces from their rhizospheres or the soil surrounding the roots. According to the development team, the strategy is “like yogurt for buildings.”

With the increased public health urgency created by the pandemic and studies showing that indoor CO2 is linked to viral transmission, the FABS team is now assessing the modules’ probiotic efficacy through extensive genome sequencing of the microorganisms the system delivers to indoor spaces. “To improve system functionality, the integration of advanced machine learning to control lighting, watering, and nutrient delivery is being implemented to maximize the plant system efficiency towards the production of the healthiest air for building occupants,” explains FABS partner Jefferson Ellinger.

Lakewood, Colo.–based Advanced Autoponics, an engineering firm specializing in data collection and automation support for living walls, is also targeting efficiency. Founded by electrical engineer Sayon Chandrakanthan, the company aims to optimize the health of indoor foliage while minimizing the need for hands-on maintenance. The firm employs a modular aeroponic and hydroponic system to reduce the use of soil, which requires more space and is more water-intensive. Clients can monitor the status of their plants remotely with mobile software. Sensors in each module can focus on individual plants, and the technology can accommodate a wide range of plant sizes and root growth patterns.

Living walls are ideally deployed not as standalone assemblies but as components of holistic circular systems. Spearheaded by Vietnamese firm Farming Architects, the VAC Library project in Hanoi demonstrates the mutual advantages of incorporating planted modules as part of microecologies. VAC stands for the Vietnamese term Vườn-Ao-Chuồng, or “garden-pond-cage,” in reference to the integrated combination of horticulture, aquaculture, and animal husbandry. As part of the project, an outdoor, wood-lattice structure provides shelter and storage for vegetable planters and chicken coops, as well as children’s books and light fixtures. The adjacent pond is home to carp, which produce waste that—combined with the chickens’ manure—is used to fertilize the plants. In turn, the plants produce food, oxygenate the air, and clean the water that replenishes the fishpond. This accessible and inviting public project represents a compelling demonstration of a largely self-sustaining, self-cleaning urban ecosystem.

Jian Mu Tower, in Shenzhen, China, by Carlo Ratti Associati
courtesy CRA-Carlo Ratti Associati Jian Mu Tower, in Shenzhen, China, by Carlo Ratti Associati

Meanwhile, an ambitious vision for the future of living walls in architecture is evident in the proposal for the Jian Mu Tower in Shenzhen, China. Turin, Italy–based Carlo Ratti Associati collaborated with agricultural innovation company ZERO to design the first so-called “farm-scraper”—a 922-foot (218 meters), mixed-use tower with more than 100,000 square feet (10,000-square-meters) of perimeter area devoted to vertical agriculture. According to the architect, the hydroponic farm will produce enough food to meet the needs of 40,000 people—approximately 270,000 kg of produce annually. While the VAC Library connects three small-scale ecologies, the Jian Mu Tower, commissioned by the Chinese grocery chain Wumart, aspires to integrate multiple agro-economic activities—food growth, harvest and preparation, market, and consumption—all on one site.

Although a pioneering idea at this scale will likely encounter challenges in execution, the grand experiment in linking human and natural systems in such an extensive way will be worth the effort. As founding partner Carlo Ratti explains, “Such [an] approach has the potential to play a major role in the design of future cities, as it engages one of today’s most pressing architectural challenges: How to integrate the natural world into building design.”

The views and conclusions from this author are not necessarily those of ARCHITECT magazine or of The American Institute of Architects.

Read more: The latest from columnist Blaine Brownell, FAIA, includes a visit to "one of the most significant memorials on the planet" found in Alabama, innovative hacks in bio materials, "zoonotic spillover" in the built environment and how architecture can address it, and a look at illegal timber harvesting.