ASHRAE Journal - May 2022 - 12
TECHNICAL FEATURE
Airborne Disease
Transmission Risk and
Energy Impact of HVAC
Mitigation Strategies
BY MICHAEL J. RISBECK, PH.D.; MARTIN Z. BAZANT, PH.D.; ZHANHONG JIANG, PH.D; YOUNG M. LEE, PH.D., MEMBER ASHRAE; KIRK H. DREES, LIFE MEMBER ASHRAE; JONATHAN D. DOUGLAS,
MEMBER ASHRAE
Signifi cant emphasis has been placed on enhancing building HVAC systems to be
more energy-effi cient in recent decades. Often, these measures include reducing
ventilation rates and overall airfl ows to achieve corresponding energy reduction.
However, the COVID-19 pandemic caused an examination of how HVAC systems may
help reduce the risk of airborne transmission of respiratory diseases via infectious
aerosols. This new goal of infection risk mitigation often leads to the opposite recommendation-that
outdoor air ventilation be increased,1 to the detriment of energy
effi ciency.2,3
To assist HVAC practitioners in understanding the
fundamental physics behind infectious aerosol transmission
and to manage the complexity of possible infection
mitigation strategies, we discuss in this article how
the overall analysis can be framed in terms of equivalent
outdoor air (EOA) delivery as a basis for infection-risk
and energy-consumption analysis. We then present the
effects of possible HVAC mitigation strategies, highlighting
cases that are particularly effi cient or ineffi cient. For
our purposes, we focus on reasonably modern central
HVAC systems typical of commercial buildings and climates
present in the United states. Overall, we would
like to emphasize the following observations made from
the cases considered:
¥ Increased outdoor air ventilation is effective for
reducing infection risk, but it can be very costly or even
infeasible depending on climate and equipment confi
guration.
Michael J. Risbeck, Ph.D., is a senior AI scientist, Zhanhong Jiang, Ph.D., is a senior AI scientist, Young M. Lee, Ph.D., is director of AI product development, Kirk H. Drees is a director
of research and modeling, and Jonathan D. Douglas is a director of healthy buildings at Johnson Controls International plc. Martin Z. Bazant, Ph.D., is a professor of chemical
engineering and mathematics at Massachusetts Institute of Technology.
This peer-reviewed article does not represent offi cial ASHRAE guidance. For more information on ASHRAE resources on COVID-19, visit ashrae.org/COVID19.
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ASHRAE Journal - May 2022
Table of Contents for the Digital Edition of ASHRAE Journal - May 2022
Contents
ASHRAE Journal - May 2022 - Intro
ASHRAE Journal - May 2022 - Cover1
ASHRAE Journal - May 2022 - Cover2
ASHRAE Journal - May 2022 - 1
ASHRAE Journal - May 2022 - Contents
ASHRAE Journal - May 2022 - 3
ASHRAE Journal - May 2022 - 4
ASHRAE Journal - May 2022 - 5
ASHRAE Journal - May 2022 - 6
ASHRAE Journal - May 2022 - 7
ASHRAE Journal - May 2022 - 8
ASHRAE Journal - May 2022 - 9
ASHRAE Journal - May 2022 - 10
ASHRAE Journal - May 2022 - 11
ASHRAE Journal - May 2022 - 12
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ASHRAE Journal - May 2022 - Cover3
ASHRAE Journal - May 2022 - Cover4
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