Committee on the Environment


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The AIA Committee on the Environment (COTE®) works to advance, disseminate, and advocate design practices that integrate built and natural systems and enhance both the design quality and environmental performance of the built environment. Expand your positive impact: Engage in our advocacy efforts. Enjoy our last newsletter (and follow us on Twitter). To learn about the Framework for Design Excellence (formerly the COTE Top Ten Measures), click here >

A big thank you to our partners: 
Founding partner: Building Green
Sustaining partners: Lucifer Lighting Company, Kingspan
Green partners: AutodeskEPIC MetalsHKS,  ROCKWOOL, WRNSSkanska, Thornton Thomasseti
Allied partners: BNIM, Leddy Maytum Stacy Architects, LMN David Baker Architects, Integral

Supporting partners: Humanscale, Mahlum, BPKC, Opsis

GAF x COTE: Looking at the Future

This 2019 video was compiled by GAF, a COTE sponsor. 

CLEARING THE AIR: The Evolving Role of Ventilation and Filtration in HVAC

By Kira L. Gould posted 08-13-2020 14:29


CLEARING THE AIR: The Evolving Role of Ventilation and Filtration in HVAC 

By William P. Bahnfleth, PhD, PE 
Professor of Architectural Engineering, Penn State 
Chair, ASHRAE Epidemic Task Force 

Due to the possibility of aerosol transmission of Covid-19, ventilation with outdoor air and filtration are receiving more attention in both professional circles and among the public than at any time in recent memory. Infrequently asked questions such as “how much outdoor air does my building really need?” and “what efficiency level should the filters in my HVAC system have?” have become subjects of vigorous debate. The answers to these questions are of high importance and, after this pandemic is in the history books, may have long term implications for built environment design. 

In simplest terms, ventilation with outdoor air replaces indoor air that contains indoor contaminants produced by the building itself, by occupants, and by indoor activities and processes. For non-healthcare facilities, a widely accepted definition of acceptable indoor air quality has, for decades, been similar to that given in ASHRAE Standard 62.1-2019: “air in which there are no known contaminants at harmful concentrations, as determined by cognizant authorities, and with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction.” It focuses, in application, on chemical and particulate air contaminants and on control of odors, in particular those associated with human bioeffluent. There is no explicit connection to health, productivity, or infectious disease prevention. 

The emerging desire to have buildings that promote wellness combined with the need for buildings that are resilient in response to challenges like epidemics seem likely to change our view of how much outdoor air is the right amount both during normal operation and during emergencies. To promote productivity and reduce sick building syndrome symptoms, some analyses suggest benefits accruing at twice current minimum levels. 

Particle filters have undergone a similar evolution. A primary initial motivation for putting filters in HVAC systems was to prevent fouling of equipment. This is still suggested by the Standard 62.1 requirement that filters be provided in systems with “cooling coils or other devices with wetted surfaces through which air is provided to an occupiable space.” Minimum efficiency filters had – and have – little ability to control fine particulate matter. 

Although it represents a significant upgrade from a previous MERV 6 requirement, the MERV 8 filters required by recent versions of ASHRAE Standard 62.1 require only 20% efficiency for 1 to 3 µm particles known to have many potentially serious health effects that result in millions of premature deaths globally every year. This does, however, give evidence of growing recognition of the importance of controlling indoor particulates because of their health effects. The standard now also includes additional filtration requirements if outdoor air does not meet regional PM10 and/or PM2.5 limits. The Covid-19 pandemic has underscored the need for better fine particle filtration to control aerosol infection risk with the result that MERV 13 filters that must capture at least 50%, 85%, and 90%, respectively of particles in 0.3 – 1, 1 – 3, and 3 – 10 µm particles, respectively, are recommended as an upgrade to existing systems. Better filtration may also be important during events that degrade outdoor air quality such as wildfires or the annual field burning that occurs in some parts of the world As in the case of ventilation, this points to a convergence of requirements for normal operation as well as resilience. 

While it is difficult to find true positives in the current pandemic, perhaps these developments in thinking about indoor air quality control will be one of them. 

COTE invited Dr. BahnflethProfessor of Architectural Engineering, Penn State Chair, ASHRAE Epidemic Task Force, to provide a snapshot of the ventilation considerations that ASHRAE, AIA, and others are considering in light of Covid-19. These issues are developing and are also being considered in the context of energy, though that topic is not included here. 

Bahnfleth recently joined forces with five other leaders in the building sector – Joyce S. Lee, FAIA, WELL AP, LEED Fellow; Mary Ann Lazarus FAIA, LEED Fellow; Kay Sargent ASID, IIDA, CID, LEED® AP, MCR.w, WELL AP; Pauline Souza, FAIA, LEED Fellow, WELL AP; Luke Leung, PE, LEED Fellow, P Eng -- to create a petition, secure hundreds of signatures from 50 countries, and send it to the World Health Organization, requesting that they take seriouesly the built environment’s role in fighting the pandemic and provide more specific guidelines about ventilation and other matters. You can see the release here, or at the IWBI site here 

William Bahnfleth is a professor of architectural engineering at the Pennsylvania State University (Penn State) in University Park, PA, where he has been employed since 1994. Dr.Bahnfleth is a past President of ASHRAE and currently chairs the ASHRAE Epidemic Task Force.  He holds BS, MS, and PhD degrees in Mechanical Engineering from the University of Illinois. He is a Registered Professional Engineer and a Fellow of ASHRAE, ASME, and ISIAQ. His research interests cover a wide variety of indoor environmental control topics including chilled water pumping systems, stratified thermal energy storage, protection of building occupants from indoor bioaerosol releases, ultraviolet germicidal irradiation systems, and others. He is the author or co-author of more than 170 technical papers and articles and 14 books and book chapters.