Speaking plainly, air filtration has never really been considered a hot topic on most people’s radars, until now. Reflecting on what we now know, perhaps it should have been. Air quality plays an important role in our health. But up until a few months ago, only wellness advocates or those in the HVAC industry had given air filtration much thought. Then COVID came and stayed, and more people began to realize that good air filtration could mean the difference between sick and healthy, and in some cases, life and death.
Offices, in particular, are a concern for companies looking to reoccupy their buildings and guarantee employees safety in terms of air quality. Ambar Margarida, Principal at Spacesmith, an architectural design firm, shared that her team is working with many of their clients on a return to the office strategy and enhancing their air quality and HVAC systems is a main part of that strategy. Spacesmith currently has projects with companies in non-profit, higher education, and financial services, and they are all “being reevaluated to see if higher rated MERV and bi-polar ionization filters can be specified in addition to increased fresh air intake and flushing out their buildings overnight or in the early morning before tenants arrive,” said Margarida.
While buildings have many options in terms of air filtration, it is important to know which are most effective, cost efficient, and compatible with their current systems. ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) recently formed an epidemic task force that will research the latest information concerning air filtration and ventilation and recommend best practices going forward.
We reached out to the task force in regards to recommendations for commercial office space and spoke with Dr. Bill Bahnfleth, Chair of ASHRAE’s Epidemic Task Force and a Professor of Architectural Engineering at Pennsylvania State University. “Systems in buildings that are being re-occupied need to be evaluated as part of a risk assessment process,” he told us. Dr. Bahnfleth also gave us a general overview of what the task force is recommending, which includes “increasing outdoor airflow during the pandemic, upgrading filters to levels that are effective for removing the fine particles produced by respiratory aerosols, and considering adding air disinfection equipment such as germicidal ultraviolet systems.”
Their response coincides with the recommendations currently listed on their website concerning infectious aerosols, but because each building is unique, it’s hard to offer more specific information. I researched a few different approaches that are currently being implemented in commercial spaces to combat infectious airborne pathogens in order to provide a more in-depth understanding of ASHRAE’s general guidelines.
Filtration basics, more than just “airhead” lingo
Large commercial buildings have HVAC systems with a wide variety of both mechanical and electronic equipment. These systems are designed based on a variety of constraints including where the building is located, typical weather patterns in that area, and air quality. One large consideration for filtration systems is size of particulate matter (PM), the microscopic aerosol particles made up of solids and liquids, that need to be eliminated. It’s important to understand PM because it plays a role in why the CDC recently changed their stance on how they believe COVID-19 is spread—not through surface contact, but rather close proximity to a carrier of the virus via droplets in the air.
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SARS-CoV-2, the virus that causes COVID-19, is transferred through droplets of various sizes that are expelled by coughing, sneezing, and perhaps even talking. Bob French is the Chief Evangelist at 75F, a tech startup that uses IoT automation to make commercial buildings more comfortable and efficient. “Larger droplets tend to land on surfaces and don’t tend to travel very far, but smaller droplets, which usually occur in lower humidity, can remain in the air for longer periods of time and travel further distances, presenting a significant risk for those nearby breathing it in,” he explained.
For the purposes of measuring air filtration, PM’s size typically ranges from 0.3 to ten microns, and it comes from a variety of sources, including pollution, dust, and, most importantly right now, microbes. Viruses are the smallest of all microbes, and size matters when measuring PM for air filtration because it determines how filters are rated. Think about catching something in a filter that you’re unable to see with a naked eye, that is how dense some air filters need to be.
Mechanical and electric HVAC systems (like the ones found in most commercial offices) use filters that receive a MERV (Minimum Efficiency Reporting Value) rating based on several factors, including the size and amount of PM that is able to pass through. MERV ratings range from one to sixteen, with sixteen being the best, filtering out 75 percent or more of the smaller PM that ranges from 0.3 to one micron in size. For perspective, operating rooms in hospitals use MERV sixteen. Standard commercial office buildings are required to use filters with a MERV six rating, in accordance with ASHRAE’s standards, but at a level six, smaller droplets under 3 microns can still pass through. Meaning, the minimum requirements for most commercial office buildings are not high enough to filter out the PM droplets containing the SARS-CoV-2 virus.
Paul Soames is the Founding Principal at Ryan Soames Engineering, based out of New York City, and he has been working with clients to get their properties ready for occupation. Soames told me how his firm is currently working with several clients to optimize their HVAC units and install BPI in their buildings scattered across the U.S. “First, you have to look at what their system is equipped to handle in terms of upgrading MERV filters to a higher level,” he said. “If you go too high, you can end up compromising air flow based on the performance of the existing fans. We felt a MERV 13 was the best choice for optimizing their current system.” To begin filtering out smaller droplets (less than 3 microns), a MERV 10 rating or higher is required; however, ASHRAE recommends a MERV rating of 13 or higher to be “efficient at capturing airborne viruses.”
BPI: tech savior or air filtration puffery?
Bi-polar ionization (BPI) is a method of air filtration that’s been gaining popularity since the onset of COVID-19. Recent reports indicate that major players, like JLL and CBRE, have moved to install this technology in their buildings in order to get employees (and patrons) to feel safe about reentry. Notable properties include the Staples Center, Empire State Realty Trust’s One Grand Central Place, and several SoulCyle locations, to name a few. With rising popularity thanks to the pandemic, it’s important for asset owners and managers to understand how the technology works and if its effectiveness is worth it to install.
Soames believes a multifaceted approach is the most efficient way to ensure people’s safety. In addition to upgrading their clients’ MERV filters, they “added BPI filters, which are relatively simple to install by just cutting a hole in the existing supply ductwork,” he said. Soames also said that installation for BPI could range “between $900 and $3,000,” making it a cost effective option. “It also runs on low voltage,” he added. Aside from easy installation and maintenance, Soames said that BPI filters have a “relatively effective track record in protecting against the flu,” but there isn’t enough peer-reviewed research to provide a more definitive statement. This is the main reason ASHRAE has not recommended BPI filtration yet. To ensure quality, “it’s important to review the unit’s specs and capabilities,” Soames said.
According to ASHRAE, BPI works by producing “high voltage electrodes [that] create reactive ions in air that react with airborne contaminants, including viruses.” However, some units can emit ozone in high levels, which when breathed in cause health complications including debilitating a person’s ability to fight respiratory infections, essentially defeating the entire point of installation. ASHRAE wants to see more conclusive scientific research to support BPI’s effectiveness, and they also recommend reviewing each manufacturer’s specifications for “ozone generation test data” to determine safety.
Automating fresh air
Detail of the Centre Georges Pompidou in Paris, showing the air intake on the exterior of the building.
What are some of the other options for improving air quality in office buildings aside from filter upgrades and BPI? This brings us back to a minor, but rather important point that Bob French mentioned while explaining the difference between droplet sizes—humidity. French had said that in low humidity, droplets tend to be smaller, and therefore viruses are more likely to spread in these conditions. A study from the American Society of Microbiology not only confirms this, but it also found that coronaviruses have the shortest survival rate in about fifty percent humidity, when compared to lower or higher rates. Humidity, along with other important factors like temperature, airflow, and system purges, can all be controlled to create an environment that is optimized to reduce a virus’s ability to thrive.
One of ASHRAE’s biggest recommendations has been to increase the amount of fresh air coming into a building. Depending on where a building is located, the amount of pollution, and the weather, changing building controls to bring in fresh air can be a guessing game for facilities managers whose buildings are not used to operating at these settings. For this reason, 75F recently came out with an “epidemic mode” for their cloud-based technology, which uses IoT and sensors to monitor and control a building’s internal environment.
“An ‘epidemic mode’ can optimize a building’s control settings based on ASHRAE’s and CDC’s guidelines but also based on that building’s needs at any given moment, in terms of load capacity, weather conditions, and so on,” French explained. “An hour later, a front might come in and lower the humidity percentage in the outside air that changes the effective capacity of the AC unit. The moment that happens, the epidemic mode sequences adjust to the new capacity to maintain optimal ventilation,” he said.
Purges are particularly effective at lowering viral transmission because they fill the entire building with fresh (filtered) air from outside, so the building is literally “starting fresh” each time. Installation length for 75F is dependent on the size of the building, but there is no networking required because their tech is “out of the box.” The cost is about half the price of traditional legacy control systems, making it a viable option for owners looking to get their buildings ready for occupancy.
Add-ons and other considerations
ASHRAE also recommends the use of additional air filters like HEPA (High Efficiency Particulate Air) units or UV-C (ultraviolet) lights to help reduce the amount of infectious aerosols in the air, but these should be viewed more as supplemental add-ons in addition to increasing fresh air and upgrading filters. Because HEPA filters are portable, don’t require installation, and are relatively inexpensive, they are a good option, especially for smaller spaces. UV-C lights are also easy to install and fairly inexpensive, but they shouldn’t be used during hours of occupancy because they can cause human tissue damage. However, UV-C lights can be used as a way to filter air by disinfecting HVAC equipment including ventilation ducts and evaporator coils, which would limit human exposure.
Some asset owners are worried about the costs associated with purges and increasing fresh air in their buildings because it consumes more energy. Dr. Bahnfleth confirmed this sentiment. “The challenge will be to raise the bar in that area while not adversely affecting efforts to reduce the energy use of buildings,” he said. Bringing in fresh air can also compromise other control settings like humidity, making it difficult to do manually. However, automated IoT technology can help reduce waste and save on costs by measuring exactly what a particular building needs and optimizing its settings to meet that need. This is yet another example of something that was previously a nice-to-have now becoming a necessity.
Asset owners and facilities managers will have to review their properties’ needs on an individual basis. Bringing in more fresh air and upgrading MERV filters is a good place to begin, but owners should carefully consider other add-on technologies like BPI, HEPA, and UV-C filters to determine how to best optimize their systems. According to Dr. Bahnfleth, “In the future, the effectiveness of these measures will need to be evaluated. Standards and codes will need to adapt to what amount to higher requirements for indoor air quality and resilience.” Unfortunately, property owners are in a position where they will have to make these choices preemptively. They don’t have the luxury of waiting to see what the latest research proves or disproves. Acting now is the only way to help people get back to work and stay safe while doing it. [Propmodo]
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