ASHRAE Journal - June 2020 - 10

LETTERS

Automatic LongTerm Thermal
Comfort
Monitoring in
Buildings
It is inspiring to read February
2020's interesting paper, "Automatic
Long-Term Thermal Comfort
Monitoring in Buildings," that summarized long-term thermal comfort
monitoring and aimed at transferring research results to professional
applications. The study was carried
out in temperate countries where
only air temperatures and humidity
values are sufficient to determine
thermal comfort. Data compiled
are useful for determining design
criteria, evaluating a system under
current practices and supporting
big data on HVAC systems for smart
cities.
However, air movement will affect
thermal comfort in tropical and
subtropical places. In addition to
monitoring air temperatures and
humidity, airflow characteristics
should be provided in determining
thermal comfort.
Local air speeds and turbulence at
occupied zones are the key factors1
in thermal comfort and should be
included in the criteria for assessing
indoor environmental quality.
Furthermore, ventilation and airconditioning design for places in
hot climate aims at providing lower
indoor air temperature and higher
mean air speed at the occupied
zones. Air turbulence would give
people a better feeling of having air
movement. This can be quantified by
turbulence intensity defined in terms
of the mean air speed and the mean
10

ASHRAE JOURNAL

ashrae.org

velocity fluctuation over a period of
time. Thermal comfort parameters
with turbulence intensity included1
is more rational and pragmatic in hot
and humid countries.
As a summary, monitoring air
temperatures and humidity is
demonstrated in the February
article to be adequate in temperate countries. Air speed and turbulence intensity are proposed to
be included in long-term thermal
comfort monitoring in tropical and
subtropical areas.

References

1. Chow, W.K., W.Y. Fung. 1994.
"Investigation of the subjective response
to elevated air velocities: Climate chamber
experiments in Hong Kong." Energy and
Buildings 20(3):187-192.

W.K. Chow, Ph.D., Fellow ASHRAE, Hong Kong
C.L. Chow, Ph.D., Hong Kong

The Author Responds
We would like to start by thanking
you for the interest you have shown
in the research we conducted and
presented in the February 2020 edition of ASHRAE Journal.
Indeed, air movement plays an
important role in occupant thermal comfort. We did not include
this in our study, and we should
have explained why we chose not
to monitor the air movement in
the gymnastics center in the article. The space that was monitored
supplied a constant airflow rate
during occupied times and did
not vary the supply air rate based
on the indoor air temperature.
In addition, the space used two
mechanical ventilation systems
that varied in design. One portion of the space was one story
high, and the ventilation air was
discharged at a similar level as the

J U N E 2020

TECHNICAL FEATURE

Automatic Long-Term
Thermal Comfort
Monitoring in Buildings

BY JUSTIN BERQUIST, P.ENG., ASSOCIATE MEMBER ASHRAE; WILLIAM O'BRIEN, PH.D., P.ENG., ASSOCIATE MEMBER ASHRAE; MOHAMED OUF, PH.D., P.ENG., ASSOCIATE MEMBER ASH RAE

Occupant health, productivity and well-being depend on indoor environmental quality (Heinzerling et al., 2013). Continuous monitoring of occupant comfort and the
indoor environment can facilitate the control of buildings for improved occupant
comfort. However, most survey methods cannot continuously monitor occupant
comfort and the indoor environment simultaneously (Peretti & Schiavon, 2011).
Instead, traditional occupant comfort surveys use onetime evaluations to estimate overall occupant satisfaction
(Peretti & Schiavon, 2011). Although there are beneﬁts to
traditional occupant comfort surveys, precisely determining occupants' preferences is difﬁcult due to the
short length of the typical survey period, relative to the
transient characteristic of comfort and the indoor environment. While some occupant survey methods have
been developed for simultaneously monitoring occupant
comfort and indoor environmental conditions, they were
typically short in duration and/or were for a relatively
small number of occupants, e.g., Hummelgaard et al.
(2007), Lawrence & Keime. (2016) and Martinez-Molina
et al. (2018). Therefore, a method is required to conduct
long-term, continuous monitoring of indoor environmental conditions and occupant preferences.
Wireless electronic survey devices have recently been
deployed in public spaces, enabling long-term, continuous reporting of occupant satisfaction. For example,

airports and public washrooms commonly use these
devices for occupants to report their overall satisfaction with the facility. In addition to the recent advancement of survey technologies, wireless sensing and
data-logging technologies are increasing in availability,
enabling long-term monitoring of indoor environmental conditions (Heinzerling et al., 2013). For example,
mobile indoor environmental quality measurement
carts combine different sensors to measure several
parameters simultaneously (Li et al., 2018; Newsham et
al., 2013). This allows for multiple sensors to be quickly
moved throughout a space while ensuring the sensors
are steady during the measurement period (Chiang et
al., 2001; Kim & Haberl, 2014). However, the carts can
be bulky, making them difﬁcult to move within and
between buildings. Moreover, it can be difﬁcult to conduct measurements when occupants are present; this
is even more difﬁcult in buildings with transient occupancy and high occupant densities.

Justin Berquist, P.Eng., is a research associate at the National Research Council Canada, Ottawa, Ontario. William O'Brien, Ph.D., P.Eng., is an associate professor in the Department
of Civil and Environmental Engineering, Carleton University, Ottawa, Ontario. Mohamed Ouf, Ph.D., P.Eng., is an assistant professor in the Department of Building, Civil and
Environmental Engineering, Concordia University, Montreal, Quebec.

occupants, whereas the second
portion of the space was two storys
high and had ventilation air discharged high above the occupants.
It was not possible to easily monitor the location of the occupants
within the space. Thus, correlating
air movement to occupant thermal
comfort responses would have
been difficult. Moreover, given the
activity within the space, it seemed
impractical and invasive to monitor the air movement within the
space.
Given the difficulties associated
with monitoring the air movement
within a space (invasiveness/occupant interference), the presented
study may not be feasible for hot and
humid climates; although, it could
be very interesting to investigate
the presented study's applicability
to such a climate, where occupant
thermal comfort is more dependent
on air movement.
Thank you again for your interest
and taking the time to reach out to
us regarding our research.
Justin Berquist, P.Eng.,
Associate Member ASHRAE, Ottawa, Ontario

https://www.ashrae.org/

ASHRAE Journal - June 2020

Table of Contents for the Digital Edition of ASHRAE Journal - June 2020