Ventilation Goes Vegetal: CASE’s Plant-Based Air Filtration System

If you’ve driven through the Bronx on the Hutchinson River or Pelham Parkways recently, you’ve likely noticed the construction of a looming 250-foot, serrated metal cube. This facility, the City’s second Public Safety Answering Center (PSAC II), is deliberately defensive — once fully operational early next year, it will house command and control center operations for the fire and police departments in the case of a major emergency in addition to operating 24/7 as a 911 call intake and dispatch center. Given the sensitive operations, the cube’s concrete structure is blast-resistant with few windows, and its building systems are designed to operate independently from outside sources of power and air should a disaster occur.

The gleaming aluminum facade and concrete armor also mask a more welcoming wall: one of plants. The Active Modular Phytoremediation System (AMPS), as the plant wall is known by its inventors at the Center for Architecture Science and Ecology (CASE), is designed to clean the building’s air from within. Jason Vollen, an architect and former associate director of CASE, was the principal investigator on the development of AMPS and is now tasked with bringing this system into its first commercial deployment. As he explains, the hurdles of this process — from the lack of certifications for new technologies to the travails of a brand new company in the public procurement process — are myriad. But Vollen also demonstrates the value of surmounting them, walking us through the benefits of the green wall technology and the potential of academic-industrial-government alliances to foster more building system breakthroughs in the very near future. –J.T.

PSAC II, designed by Skidmore, Owings & Merrill LLP | Photo © SOM
Jonathan Tarleton (JT):

Tell me about the Public Safety Answering Center (PSAC) II project and the Active Modular Phytoremediation System.

Jason Vollen (JV):

PSAC II will be New York City’s second 911 call center, providing redundancy to the existing center in Brooklyn and operating 24/7. Because it will be a secure facility, workers can’t easily go outside to get fresh air — and if they could, they’d be right near the intersection of the Pelham and Hutchinson River Parkways in the Bronx. That makes indoor air quality especially critical.

As the associate director of the Center for Architecture Science and Ecology (CASE) — a research group cohosted with Rensselaer Polytechnic Institute and Skidmore, Owings & Merrill (SOM) — our team worked on designing a system to improve air quality. SOM was contracted by the New York City Department of Design and Construction (DDC) to design PSAC II, so we worked alongside them to develop a new kind of air filter: our Active Modular Phytoremediation System (AMPS).

Detail of AMPS prototype | Photo by Ted Ngai, courtesy of CASE/RPI

With AMPS, we’re trying to clean the building’s air from within using a wall of plants. If you don’t have to continually take outdoor air into your building and can instead clean what’s already inside, you significantly reduce the energy load of the building’s HVAC system. And in the case of an attack, the PSAC II facility would shut down its outdoor air intake, so the ability to create fresh air from within for an extended period of time is really important to security. Finally, the plant wall provides a calming workspace for individuals that will be dealing with stressful situations.


How does the development of this system fit into CASE’s mission?


CASE was started as an academic-industrial alliance with the goal of fostering the next generation of building technologies. We wanted to take the typical development and implementation time of game-changing technologies and cut it in half: from 15 to 30 years to 7 to 15. Seven years into CASE, here we are installing AMPS in a building.

In order to do something new you have to pull together true multi-disciplinary collaborations. I’m trained as an architect, but I also have an affinity for material science and energy systems in my blood. Our team worked with plant scientists, microbiologists, and other specialists typically far afield from architecture based at Rensselaer and in the NYC area to develop AMPS. That sort of collaboration is where we’ll see more inventions coming from in the future.

Plant systems can act as effective air cleaners by leveraging phytoremediation. | Image courtesy of CASE/RPI

Walk me through the system itself — how does it function?


The system is what we call a biomechanical hybrid. The building’s HVAC system pulls return air — air that’s been used by occupants, which also contains off-gassing from the building — through a wall of cassettes, each of which holds a plant. We’re using Golden Pothos, which is not always the most attractive plant in a house, but it’s a high performer and actually looks quite wonderful in a vertical wall. One reason people keep them is they’re almost impossible to kill, which was another important criterion for us.

As the air moves through the wall, it comes in contact with the plants’ root rhizosphere. This micro-ecosystem surrounding the root ball contains a variety of microbes that feed on the sugar produced by the plant as you water and feed it. Those microbes in turn eat contaminants present in all indoor air, including the volatile organic compounds (VOCs) and formaldehyde produced by off gassing that is present in all buildings but particularly prevalent in new ones. The microbes make these contaminants inert, and the air comes out cleaner on the other side.

We’re linking human health to a diverse group of microbes, and we’re also linking energy bills to that same group of plants.

At PSAC II, the wall is a lobby-sized installation, which is relatively large for a green wall. The idea is not to take the entire building in a new direction; it’s to go far enough to show that the system works to clean the air and take some of the load off the building’s HVAC system. We’re linking human health to a diverse group of microbes, and we’re also linking energy bills to that same group of plants. That’s relatively novel in a building system.

In this case, we didn’t fully redesign the building’s mechanical system in order to integrate AMPS; we just altered some things to pull the air through the wall and enable a targeted area to be serviced by the system. In the future, we’d ideally be engaged in a potential project from day one as we were with PSAC II; otherwise, there’s always more compromise when certain things are set. But the system could be installed in almost any building.

Section diagram of AMPS depicting the filtration of air through the green wall system, providing clean fresh air. | Image by Matt Gindlesparger, courtesy of FABS

One doesn’t normally think of a public project like PSAC II as a natural host for the first deployment of a new technology. Did the public nature of this project abet the implementation of AMPS or did it present challenges?


The Valley of Death in product development is being the first person to install something that has never been tested in a building before. Who wants to do that? It requires a very select type of client, an appropriate budget, someone who believes in the mission but also has a responsibility to take chances. If they don’t take chances on new technologies, they risk not developing them for the rest of their portfolio. The City of New York ends up being one of these important client groups — they are a huge real estate owner, and they have a lot of people working for them.

The core of the mission of the Design Excellence program in the City’s Department of Design and Construction is to lead by example. The project was really the perfect storm: the right client in DDC, the right product, the right group at SOM on the design side, and Tishman, the project’s construction coordinator — everyone working with us and educating us in the best way to navigate the procurement process. Without all of these groups aligning in the same direction, I think it would be impossible to try to do something like this.

We think that AMPS can ultimately be the lungs of a building.

There were, of course, several challenges, and the process was a long one. I think we started working on it at the end of 2008. As an economic model, our approach is fascinating: we essentially pursued the development of AMPS in parallel with the larger PSAC II project without any direct funding from research grants, government, or venture capital. We said, “We would like to study this at no additional cost to you right now and if it works out, then we’ll figure out if it is worth deploying and come up with a way to do so.”

Once we were able to demonstrate the viability of the system, its development became contract-based, which could provide a new model for developing next generation building materials that provides value to the client at the same time. You don’t have to go to venture capital investors who want returns in two years. You can’t get returns that fast in building products, so typical investing doesn’t really work in this space.

AMPS prototypes | Photos courtesy of Jason Vollen

How did AMPS move from the research phase to installation?


To move from incubation into commercialization and manufacturing, every technology needs to leave home. For AMPS, that home is CASE. Because there’s no green wall manufacturing market in which to shop around, we either had to give the technology to someone else to implement for the first time or do it ourselves.

In the end, it was easier for the inventors to form a company, Fresh Air Building Systems LLC (FABS), to move this technology as a product. But it’s one thing to be a researcher and develop technologies that could move in the marketplace and another thing to go through the contractual work and liability issues that you have to get the product into a public building. To go through the mountains of paperwork for procurement with a newly formed company can be quite daunting, and that process took two years of collaborative work with the Department of Design and Construction and Tishman.

There were also regulatory considerations, the first being, who certifies this system? There is no specific UL or CSA listing [two types of consumer safety product certifications] for this kind of product. We have to break down the components to identify the potential risks and determine how to certify each of those. Then there’s the larger regulatory issue in the future when we will go to American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and encourage them to create a code around this kind of system. In order to do that, there’s nothing better than getting data from a building installation to show them the results.

Detail rendering of AMPS components showing modular cartridge assembly | Image courtesy of CASE/RPI

How will the system be maintained?


CASE is continuing to conduct research on the system and provide design work on the plant medium and lighting, and FABS is delivering all of the components for installation and holding the liability. The work is still a collaborative effort and will probably continue to be. Like any new technology, AMPS will improve through innovations at CASE as well as solutions FABS finds in delivering the system in a cheaper way.

Maintenance is, of course, one of those big issues. FABS and CASE will handle the long-term operation and maintenance of the PSAC II system through a contract with the building’s management company. In other living systems, you can see as much as 30 percent die off. Some die off is natural, but we’ve seen a lot less in our laboratory prototypes, so we expect less at PSAC II. Our cassettes are also designed to plug and play — you can pull out a cassette with a dead plant and put in a new one without disrupting the flow of the building. If they’re designed right, systems like AMPS that react to dynamic conditions perform better over time, and we expect that will be the case at PSAC II.

PSAC II in construction in 2013 | Photo via NYC DDC.

How will the system be monitored and tested?


We’re looping the air cleaned through AMPS back to several rooms where we can test it for oxygen, carbon dioxide, pollutants, and VOCs. Our measure of success is to clearly identify the difference that makes a difference — to show that this plant wall system can lower the amount of VOCs while also lowering energy use.

Right now we’re not looking for large numbers. But we will continually adjust the variables — water, nutrients, and lighting — to make sure that we get the best performance. Over time we would also love to be able to do softer surveys on worker productivity, health, and well-being. That will be dependent on what the people running the building want going forward.

In a building integrated situation, there will also be new variables. We have to continue to understand how the performance may change if the variables do. But the good thing about projects like this, just like any high performance building, is that there are so many smart people looking at and thinking about it that the likelihood of something going wrong is much lower than a regular building. It’s over-engineered; it has to be. Everybody wants this system to survive and win.


What is the long-term vision for this kind of system?


We think that AMPS can ultimately be the lungs of a building: cleansing and rejuvenating the air itself. You can imagine every system having a filter like this in it. You could eventually almost replace traditional HVAC systems with biomechanical hybrids that have the ability to dynamically ramp up or down depending on the quality of the air in real time. There will always be a certain amount of control that one will need, but the idea that you could make those systems smaller and simpler and make them work in conjunction with biotic systems is very real. There will always be redundancies in buildings — there have to be — but it’s a matter of balance. And once the system’s engineered as far as one can engineer it, then the next step is going to be engineering nature to do the work. That’s on the horizon.

Jason Oliver Vollen, AIA, is Principal of High Performance Buildings at AECOM. His research and practice is focused on leveraging the intersection of energy, finance, and policy to deliver high performance and sustainable design solutions that reduce both capital and operating costs and are net zero wnergy capable. Prior to joining AECOM, Vollen was the Associate Director at the Center for Architecture Science and Ecology, an academic-industrial research alliance between Skidmore, Owings and Merrill LLP and Rensselaer Polytechnic Institute, where he was a tenured professor. His research focuses on a multidisciplinary integrated approach that takes advantage of the first principles of building physics to develop next generation building systems that provide lower energy intensities while improving occupant comfort. Vollen’s research has been funded by the NSF, DOE, NREL, NYSERDA, and the AIA. He has won numerous awards for next generation building system design and has multiple building system patents under review.

The views expressed here are those of the authors only and do not reflect the position of The Architectural League of New York.


p w anderson, phd November 4, 2015

This system employs a monoculture, which – although efficient when healthy – might be wiped out by a plant pathogen. Particularly, a pathogen that spreads in the air such as a fungus [via spores release] or an insect, could quickly give you a yellow or brown wall. Spraying or fumigation to control the pathogen within the closed atmosphere would be problematic. A carefully selected mixture of plants might be useful. I suggest consulting a horticulturist or plant pathologist. Good luck!

Giuseppe Fanciullo November 25, 2015

If the system works indoor, could I have more information regarding how do you provide the necessary light? are you providing artificial grow light? and in this case is it efficient?
Thank you.