ASHRAE Journal - September 2020 - 45

MANUFACTURED
IN ROCKMART, GA

hours are expected to move from Zone 1 into Zones 2 and
3 shown in Figure 3. If the building being analyzed has
less than a 24/7/365 duty cycle, daytime ambient conditions in cold climates will have more ambient hours in
Zones 2 and 3.
There appears to be a direct correlation between low
indoor RH and artificially high air change rates with the
spread of airborne pathogens in winter. If we can cost
effectively maintain a 40% to 60% indoor RH in winter while simultaneously reducing supply and return/
exhaust VAV fan energy costs, why not do it? Quoting
another ASHRAE Journal author from a recent column,
"...but for most building types, we have yet to find any
that perform better on a life-cycle cost basis than a 'well
designed' VAV system."27

COVID-19 Pandemic and ASHRAE
Best Practices for Mitigation
After the substantial completion of this article
and prior to its publication, an ASHRAE Epidemic
Task Force was formed that is chaired by William P.
Bahnfleth, Ph.D., P.E., Presidential Member/Fellow
ASHRAE. At that time, the SARS-CoV-2 virus had
shown itself to be an airborne pathogen easily spread
indoors by an infectious aerosol. The Epidemic Task
Force recommends the following steps to mitigate the
spread of COVID-19 indoors.
* Air-handling systems that permit building air recirculation should increase outdoor air ventilation above
code minimums, and consider installing MERV 13 filters
if they are not in place.
* Control indoor relative humidity between 40% to
60% RH.
* Flush the building prior to occupancy with all
outdoor air to remove any residual infectious aerosols
indoors.
The authors would like to point out that all three of
these remedial actions are addressed in this article. The
section entitled "Morning Building Prehumidification
and Warm-Up Control Strategy" would need to be
accomplished with all outdoor air in lieu of recirculated
air.

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Acknowledgments

us.info@miuraz.com
888.309.5574
miuraboiler.com

The authors would like to thank United Metal Products
of Tempe, Ariz., for their assistance in providing custom air-handling unit costs for the direct evaporative
SEPTEM BER 2020

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ASHRAE Journal - September 2020

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