Ventopenings: Conditioning in Pandemic Times. Part 3—A Conversation about Air Quality
This is the third, and final, post in a three-part series. Click on the links for part 1 and part 2.
In this piece, we bring together the architects Ahu Aydogan and Dorit Aviv along with the architectural historians Daniel A. Barber and PLATFORM’s Marta Gutman to discuss air quality during the pandemic (Figure 1). Daniel, an historian of architectural environmentalism, convened this discussion inviting Ahu and Dorit, designers and researchers specializing in the fields of energy and ecology, and Marta, an historian of children’s spaces, to the “table.” This is a transcript of the spirited conversation that took place over Zoom, and it has been edited for clarity and length.
Figure 1. The authors discussing this topic on a Zoom conversation, convened by Daniel A. Barber on October 1, 2020. Photo credit: Daniel A. Barber.
Daniel Barber (DB): I’m happy to bring us together to discuss air quality, air change, and their relative mechanical and non-mechanical aspects, capacities, and potentials amidst the pandemic. I have been thinking about these issues in schools, and other interior spaces that require a new kind of care and attention. Why doesn’t everyone introduce themselves and some of their relevant research?
Ahu Aydogan (AA): I am working on building integrated plant-based systems that are connected to heating, ventilating, and air conditioning (HVAC) systems: they clean indoor air and save energy by reducing outdoor air intake.
HVAC systems need to deliver outside air into buildings, which is filtered and heated in the winter or cooled in the summer. There is a dilemma between improving Indoor Air Quality (IAQ) and energy efficiency (which means buildings have to be sealed). However, IAQ problems arise if buildings are too tight. You have to sacrifice one to achieve the other, unless you use natural ventilation. I reduce outdoor air intake by using plant-based systems to clean indoor air. In this way, I satisfy IAQ and reduce energy consumption (Figure 2).
Figure 2. Modular filter of the plant-based system. Photo credit: Ina Dajci, 2019.
DB: Does what you just mapped out offer a method for addressing the novel coronavirus? What contingencies does it introduce? Has the virus played a role your desire to increase outdoor air intake?
AA: The straightforward answer is yes: the virus plays a major role. Outdoor air intake has to be increased to improve IAQ. Since most HVAC systems are not designed with efficient filters, ones that counter viral spread, we have to rely on passive techniques (open windows!) for ventilation now.
We use natural ventilation in our apartments and houses. Other buildings, such as office buildings and schools, rely mostly on air filtered through HVAC systems. The minimum efficiency reporting value (MERV) measures the efficiency of filters in capturing contaminants. In many HVAC-reliant buildings the MERV value is below 16, but for some, like surgical rooms in hospitals, it runs to about 17 to 20. If equipment cannot reach a high MERV value, then what is the point of adjusting HVAC settings to move around infected air? Regularly changing filters is one possibility but remember the virus, because of the size, about 0.1 microns, can easily pass through standard filters. We are approaching a systemic issue in a piecemeal fashion during the pandemic. Winter is complicating things further, reducing access to natural ventilation.
“When combined with natural ventilation, radiant systems present an energy-efficient alternative, which allows for design expression.”
Dorit Aviv (DA): I can add to that. Both the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and the Federation of European Heating, Ventilation and Air Conditioning Associations (REHVA) have recommended more fresh air intake in response to the pandemic. As larger volumes of air require conditioning our current HVAC paradigm leads to increased carbon emissions, an example of the nexus between energy and air quality.
We have airtight envelopes that are meant to create energy savings for air-based HVAC systems. Limiting fresh air intake led to the sick building syndrome (SBS) in the 1980s. In response, ASHRAE recommended higher standards of fresh air intake—meaning more ventilation, heating, and cooling, as Ahu has just described—which has led to energy and air quality always being in opposition.
My research explores how to shift away from this paradigm, ventilating buildings by non-mechanical means while maintaining thermal comfort levels. I have been working on radiant systems that do not rely on pre-conditioning outside air. They are based on heating or cooling surfaces—floors, ceilings and walls—using embedded water pipes (Figure 3). This dramatically reduces overall energy use. When combined with natural ventilation, radiant systems present an energy efficient alternative, which allows for design expression. So, you can open the window, maintain airflow, and achieve the thermal control we are accustomed to inside buildings.
Figure 3. Infrared photograph and diagram of a radiant floor, showing hot water pipes embedded in the concrete slab. Credit: Dorit Aviv and Sean Rucewicz, 2020.
Now, the cooling capacity of radiant systems used to be limited in hot-humid climates. However, new research shows that you can use radiant cooling without condensation in tropical climates. We developed a photonic membrane that separates the cooled surfaces from the humid air but still transmits thermal radiation (Figure 4). This allows for entirely naturally ventilated environments while still maintaining thermal control across different climates. This is one way that I’m trying to tackle the dichotomy between air quality and energy consumption, together with an international group of researchers.
Figure 4. Diagram of radiant cooling panels with a special membrane that enables cooling without air-conditioning in hot-humid climates. Credit: Dorit Aviv and Jiewei Li, 2020.
In this regard, Daniel, I am thinking about the discussion in your PLATFORM post of surviving in summer without an air conditioner. In some climates, hot climate is year-long and this is getting worse with global warming. So, heat stress is a huge problem and cooling becomes even more important to keep people healthy. We can’t give up cooling, but we need to rethink how we achieve it.
My research related to air quality during the COVID-19 pandemic has evolved out of my work on light simulations in different wavelengths, not just visible light but also infrared and ultraviolet radiation. An expert on airborne transmission has asked to use my studies to advance ultraviolet germicidal irradiation (UVGI). This technology uses UV light to sanitize the air in occupied buildings. However, UV radiation is also dangerous for human eyes and skin, so I assess how to use this equipment in buildings and disinfect the air without putting people at risk. In an early application, UVGI equipment was installed in a school in Philadelphia to prevent the spread of measles in 1937. This is related to the question of schools that you brought up—how to ensure those environments are safe and how to combine technologies to ensure air quality.
“The guidelines and standards, the filter ratings, and the related equipment do not consider the virus. All of this has to be revisited. ”
AA: I have an addition to Dorit’s thoughts regarding UV. NASA started experiments with plant-based systems because astronauts were having problems with air quality. Bill Wolverton, a scientist at NASA, also used a UV filter: air was filtered by plants and passed through the UV light, to eliminate viruses, bacteria, and other pollutants before it was returned to the indoor environment.
DB: I like to think of our HVAC systems as being as much about people conditioning as air conditioning. That we have become accustomed to a certain way of life, and now that way of life is changing. This point has come up implicitly in your comments, this sense of how to shake us out of our current cultural patterns and building practices. The solutions being discussed for schools are still about technical fixes: turning up the ventilation, adding filters, adding gadgets to the toolkits for acclimatizing the interior environment; still little about the patterns, processes, and life habits and how they can produce similar air quality and health effects.
DA: Architecture has struggled with these issues since the energy crises of the 1970s. Curtain wall construction and attempts to reduce energy losses through infiltration led to making our buildings more tightly sealed, less available for other interventions. Today, an open window is already a big paradigm shift. It is not just another tweak to the system, it disrupts the system because it allows unconditioned air into a thermally isolated environment. We need to rethink the way we build to make our daily interior environment more livable.
DB: Do you see the coronavirus intersecting those needs and processes? Does the pandemic provide some avenues for changing the cultural relationship to mechanical systems?
DA: My hope is that pandemic is a catalyst for not repeating that cycle that we have seen with the sick building syndrome. Simply increasing the air exchange rate will bring energy consumption up, which in turn increases buildings’ carbon footprint. This pandemic could be an incentive for pushing outside of that pattern, switching things up.
Marta Gutman (MG): I do not often have the privilege of listening to really smart people talking about technology in such understandable and provocative ways. I have a question about the number of people inside rooms. When architects design schools, they address this question through a concept called utilization, the relationship between the human capacity of a classroom (the number of students for whom it is designed), and the number of students who are actually there. Is the room overutilized? Or underutilized? The question that comes to mind with regard to the pandemic is: Do we need to create a new capacity for the classroom? Will the pandemic change utilization in schools?
AA: ASHRAE 62.1 specifies ventilation rates for interiors, relative to how much fresh air is needed for hospitals, offices, and many other kinds of spaces acceptable for occupants. We need this utilization number to understand human use, and to circulate carbon dioxide. For an office building, twenty cubic feet per minute (CFM) per person is required. However, the guidelines and standards, the filter ratings, and the related equipment do not consider the virus. All of this has to be revisited.
Daniel asked how these parameters need to change. Codes and standards are related to the conditions we live in, and they change and adjust. Take outdoor dining in New York. I was away this summer, and when I came back to the city, I said, this is great! Why not think of buildings in the same way? Can we manage to live in a different way? To make them warm and beautiful? As we rethink HVAC, maintenance, filter values, and natural ventilation, the premise of the design will change.
MG: What happens if the human load of a classroom is reduced? What happens to the thinking about air exchanges, about the number of plants that you need to filter the air or how the radiant heating works, when the number of students goes from thirty to ten? Can we discuss how many people there are in a room and the design technology needed to keep people safe and healthy? We need to bring the social side and the technological side together to come up with new, better, and more humane ways to make architecture.
AA: I agree entirely. When people are working on the technical side, they think the answer is a matter of calculation. It is important for engineers to understand how technology affects people's lives. People do not think about air cleaning in HVAC unless they have a headache or get dizzy. But they sometimes do understand that plants are putting them in a good mood (Figure 5).
Figure 5. The plant-based air filtering system prototype. Photo credit: Gilbert Santana., 2019.
DB: In this discussion we see that interior spaces and thermal concerns have been a part of this broader technical machine—of energy systems, building practices, etc.; in commercial, residential, and educational setting. The project has been to calculate the variables carefully to maintain a level of knowledge and exactitude in terms of how the air quality of those spaces is experienced. All of this has been controlled and in the context of carbon-based systems.
Part of what I hear is that relative to the coronavirus we are seeing how charged these spaces are, how emotionally and psychologically and socially full our interiors have suddenly become; we also confronting some precise questions about how to treat a classroom differently. I guess what I mean is that the social and emotional charge of the interior has changed dramatically with the coronavirus. We have rearranged our houses to accommodate and to adapt our spaces, work from home, remote schooling, etc. Now, that gives us a different sense of the constraints and the possibilities of the interior. We are asking for different things, and need to keep this ventilation/carbon/virus nexus very much in our sights.
DA: That question of the interior/exterior has become very evident because the vast majority of infections have happened indoors. In relation to the school question, social distancing is not enough to mitigate virus spread in closed environments, if we assume SARS-Cov-2 spreads through airborne transmission. The specific airflow pattern and mixing over time within a closed space may cause aerosol transmission from one person to another, even if they are six feet apart. So instead of simply reducing density, can we consider how to make our buildings more like the outdoors in terms of the airflow? And how do we do this without a massive increase in carbon emissions?
DB: What should we be doing now relative to the questions of air quality, ventilation, and non-mechanical heating and cooling in apartment/classrooms? Are you currently working on responses to these problems?
“An open window is already a big paradigm shift . . . it disrupts the system because it allows unconditioned air into a thermally isolated environment.”
AA: I have not worked with a virus previously, but I have studied IAQ pollutants. Alternative techniques for ventilation and air filtering need to be investigated. In my research, plants grow in hydroponic media, and I use activated carbon as an absorption material, so I studied the activated carbon’s absorption capacity of virus-related particles. More research needs to be done with plants and how they can metabolize viruses. Disinfection with UV light is also a useful first step.
DA: What we can do is open the windows. It is as simple as it sounds. People do not really do that. In the United States, even in some apartment buildings, it is not always possible to open the window. The bigger question is, again, how do we make interior environments more livable? That is a big focus of my research. Radiant systems are relevant in cold climates, where people close windows during the winter, and in hot climates, where people do not open windows if they have an air conditioner. So, how do we change that? How do we start making other ways of heating and cooling available, and really push for the open window?
MG: C.B.J. Snyder, the architect in charge of school construction for the New York City School Board in the Progressive Era, designed classrooms with big windows and movable partitions. In the late 30s, 40s and 50s Snyder's buildings were discredited—the moveable walls and ample windows were described as old-fashioned, poor ways to design, in contrast to the new sparkling modernism. People change, the ideas change. They need to change again!
DB: As you put it, the desire for sparkling modern spaces, has led to a number of unintended consequences that we are now struggling with. I think part of what Dorit and Ahu are doing are re-examining the tools, practices, and strategies for adaptability, in contrast to the sort of consistency and universalist conceit of a lot of twentieth-century architecture.
MG: One comment on open windows. I do not have air conditioning; I count on ceiling fans to cool my house all summer. The windows are open too, and this produces challenging intersections with people who expect your windows to be closed. Smoke and noise coming from the street become part of your life. We engage, intersect, and connect with many aspects of our worlds when we open windows.
DA: This is something that Ahu touched upon earlier. Places with high concentration of air pollution face a huge barrier to natural ventilation. Daniel asked, can this pandemic encourage something positive for the future? It takes effort but it is not impossible to limit air pollution. We need clean air in order to allow people to ventilate interior environments, and we need to push for further policies to limit air pollution.
DB: A good spot to end, perhaps, both the swirling complications of our air-policy problem as architectural, industrial, and epidemiological . . . and also some optimism. Thanks to all of you for participating in this discussion!
