ASHRAE Journal - January 2021 - 25

TECHNICAL FEATURE

Completing this step will allow a building owner to
get ahead of these potential problems. If a retro-commissioning program is not followed, there is a risk that
occupants may ﬁnd the building a bit stuffy or humid-
and rapidly attribute that feeling of discomfort to an
" unhealthy building. "
While the issues of ramping up operation, occupant
comfort and building health may be separate, they're
easily blended in a situation like the one building occupants will be facing. Ample evidence exists that poor
HVAC performance can negatively impact indoor air
quality and result in the building being labeled a " sick
building. " If systems are not optimized for comfort and
health, a " sick building " can lead to a partial or even a
full closure. Buildings still ﬁne-tuning HVAC operation
to meet today's varying occupancy demands face this
same risk. As a result, verifying that HVAC systems are
functioning as intended becomes an important part of
the overall strategy of assuring building occupants of an
as safe as possible return to work.
Inspection and testing could also verify whether a
real risk of infection exists beyond SARS-CoV-2. As
long-empty buildings' water systems come back online,
building occupants face a far greater risk of adverse
impacts from mold spores or infection from Legionella
bacterium than they do from SARS-CoV-2.22 Both mold
and Legionella are living, viable organisms found in
damp areas (in the case of mold) or water supplies (for
Legionella). The CDC notes22 that each of these organisms may remain viable for weeks or months, depending
upon building- and plumbing-speciﬁc factors, including water heater temperature setpoints, water use patterns, disinfectant residuals and preexisting Legionella
colonization.
Humidiﬁcation systems, cooling towers and other
HVAC equipment tied into water systems that have not
been appropriately treated could generate infectious
droplets that are respirable in size. (See ANSI/ASHRAE
Standard 188-2018, Legionellosis: Risk Management for
Building Water Systems,23 for guidance.) Those droplets
can be drawn into the mechanical systems and increase
exposure risks.

Taking Steps to Return to Normal
A thoughtful, methodical approach to preparing buildings for re-occupancy can minimize the risks noted
above. Now is the time to qualify the quality of the

indoor environment through a targeted inspection and
testing program to ensure a " clean bill of health " prior to
re-occupancy, and to document that the facility is meeting the appropriate standard of care. (See Reference 1
for additional guidance.) This will help ensure a safe
and healthful environment for occupants and minimize
legal and reputational risk for building owners and
managers.
You might think of this check as your " preﬂight checklist. " Before any ﬂight takes off, the ﬂight crew will work
through their checklist to make sure all components are
operational before they actually back away from the gate
and move to the runway. To assure building occupants
that the physical work environment is as safe as possible,
it will be critical to likewise run through a performance
checklist that veriﬁes that all building components are
functional, operating appropriately and meeting performance requirements before reopening the building.
Now is the time to look at building systems in a more
comprehensive way. Too often building operators focus
on problems in isolation, such as shutting down dampers in one area to move more air to another trouble spot.
Before long, the entire system has fallen out of calibration of ventilation air (ﬂow rates, diffuser velocities)
and related hydronics from the original design intent.
Depending on the complexity of a building's HVAC
system, a veriﬁcation process, including commissioning or recommissioning, may be necessary to ramp up
the system and ensure it is performing to as-designed
performance or to the conditions necessary for the new
occupancy demands.
In addition, building managers should carefully
examine each of the recommendations being offered
currently to increase the amount of outdoor air being
brought into the building. Some suggestions include
limiting recirculated air by going to 100% outdoor air
or, if that's not possible, to increase air ﬁltration with a
higher quality ﬁlter.24 The truth is, these adjustments
can drive tremendous thermal imbalances as zones are
turned on and off to reﬂect local occupancy density, as
well as provide major challenges in appropriately conditioning the air. Although general guidance recommends
staying within system capacity, adjustments made to
reﬂect changing occupancy may disturb the air balance
of the system. In those cases, a better solution may be to
increase the efﬁciency of ventilation air, especially when
system limitations will not allow increasing the amount
JAN UARY 2021

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ASHRAE Journal - January 2021

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