ASHRAE Journal - February 2020 - 16

TECHNICAL FEATURE

occupied hours, 21.2°C (70.2°F). Knowledge of the ideal
temperature in the gymnastics center (on the basis of
minimizing warm or cool votes) allows the building
operators to adjust temperature setpoints to improve
average occupant thermal comfort. However, given that
the location of the case study building is in a heatingdominate climate, adjusting the setpoint downward
instead would serve to save a modest amount of energy
on an annual basis.
Although the case study used in this article showed the
capabilities of the proposed method, it has some limitations. There is a risk that the participants are self-selecting or there are other biases, potentially leading to the
selection of a setpoint temperature that is not optimal
for the group of occupants. To estimate whether there
was a response bias-whether uncomfortable occupants
were more likely to vote-Berquist, Ouf & O'Brien (2019)
compared all button push events to motion detection events (as a proxy for occupancy) and indoor air
temperature. Results showed only minor peaks in the
frequency of survey responses at cooler and warmer
temperatures, indicating that this potential form of bias
is insignificant. However, even if it were to become significant if applied to buildings, it may not entirely deter
the selection of an appropriate setpoint. If it is assumed
that only dissatisfied occupants vote and an inappropriate setpoint temperature is selected by the operator, satisfied, non-voters, would become dissatisfied and begin
providing feedback. In turn this occurrence would cause
some of the initial non-voters to begin voting. This may
repeat until the setpoint temperature that satisfies the
greatest number of occupants is converged upon.
In addition, the current scheme is open-loop, requiring manual interpretation of the results and corresponding adjustments to setpoints. In the future, this
process could be automated whereby votes directly
control the temperature setpoint, using the building
automation system (BAS). Bridging the gap between the
survey method and the BAS could allow for improved
occupant thermal comfort, while also considering
changes in seasonal occupant preferences and changes
in occupancy itself.
In addition, language barriers or misinterpretation of the survey questions could be an issue since
the researchers were not present while participants
responded. Finally, although the devices were clearly
labeled, no additional mechanisms ensured that
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ASHRAE JOURNAL

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FEBRUARY 2020

occupants followed the instructions and only responded
to the survey question once per session on their way
out of the facility. This would have been possible if the
entrance and exit of the room were different. Future
research should aim to address these limitations and
build on the presented approach.
While one alternate possibility for estimating optimal
indoor conditions for thermal comfort is a bottom-up
modeling approach, such as the Fanger thermal comfort
model (ASHRAE, 2017), there is significant uncertainty
about personal parameters (i.e., clothing level and
metabolic rate). Moreover, the metabolic rate of the
gymnasts is significantly higher than those for which the
Fanger model is intended (ASHRAE, 2017). In addition,
correlating different indoor environmental parameters
to occupant comfort for the control of buildings for
improved occupant comfort should be explored. For
example, using various indoor air contaminants and
occupants' perception of indoor air quality for the control of ventilation. For the current case study, chalk dust
was anecdotally revealed to be the most problematic
contaminant rather than traditional surrogate contaminants such as carbon dioxide.

Conclusion

This article presented a method to conduct long-term,
continuous occupant comfort surveys using electronic
survey devices in conjunction with continuous temperature and relative humidity measurements. This approach
can provide thousands of unique data points to assess
occupant comfort and its relationship with indoor environmental conditions. This article demonstrated how
survey results could be used to improve building temperature setpoints for occupant thermal comfort. The
method was tested in a gymnastics center which gathered over 2,000 responses related to occupant thermal
comfort. The responses were compared to the measured
thermal conditions in the preceding hour. The results
indicate that the occupants' median preferred temperature (i.e., the median temperature corresponding to
neutral votes) was 21.7°C (71.1°F). Further details on this
study and the comprehensive data analysis, including
results separated by males and females, are provided
in Berquist et al. (2019). However, skewed results could
arise due to miscommunication or repetitive unrepresentative responses. Future research should build on the
proposed method by extending it to feed results directly

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ASHRAE Journal - February 2020

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