ASHRAE Journal - February 2020 - 12

TECHNICAL FEATURE

FIGURE 2 Psychrometric chart showing the frequency of average air temperature and relative humidity measurements during occupied hours in the gymnastics center.

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Because of the uncertainty of the exact location of the
occupants during the preceding hour, the average of the
seven temperature and relative humidity measurements
was used to represent the thermal conditions in the
gymnastics center. The researchers hypothesized that
the air in the space (which is controlled via a forced-air
system) is relatively uniform in temperature and relative humidity. To test the assumption of homogeneity,
the instantaneous differences between measured values
was calculated. To confirm, the mean and maximum
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Percentage of Occupied Hours

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Data Analysis

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The thermal environment (temperature and relative humidity)
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inside the gymnastics center was
monitored with seven sensors
evenly distributed throughout the
space, as shown in Figure 1. Each sensor covered an average of 226 m2 (2,429 ft2) in the single thermal zoned
environment. For temperature, the deployed sensors
have a measurement range of 0 to 50°C (32 to 122°F),
accuracy of ±0.21°C (±0.38°F), and resolution of 0.024°C
(0.043°F). For relative humidity, the deployed sensors
have a measurement range of 0 to 90%, an accuracy of
±2.5%, and resolution of 0.05%. The sensors were factory
calibrated and after preliminary testing, were installed
at a height of 1.5 m above the floor. To ensure adequate
memory and battery capacity, the devices logged measurements every 10 minutes over the six-month period.
Occupants were instructed to respond to the survey
after their gymnastic session (assumed to be one hour).
Therefore, the average temperature and relative humidity measurements over the hour prior to each survey
response were used to correlate the thermal environment to the occupants' satisfaction during their session.

ASHRAE JOURNAL

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Saturation Temperature (°C/°F)

Indoor Environment Measurements

Humidity Ratio

the ideal thermal environment for
all occupants is determined. The
two occupant survey devices were
installed with the following question posted above "How satisfied
were you with the temperature in
the gymnastics center today? Were
you..." Possible responses were as
follows: "Warm, slightly warm, neutral, slightly cool, cool."

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Dry-Bulb Temperature (°C/°F)

of the standard deviation of the instantaneous differences between air temperature sensors during the study
period were calculated; the results were 0.35°C (0.62°F)
and 1.02°C (1.84°F), respectively. Accordingly, it was
deemed adequate to use average conditions among the
seven sensors to characterize the space conditions, as
experienced by the occupants. Three plots were created
to visualize the thermal conditions and corresponding
thermal comfort in the space. First, the frequency distribution of the temperature and relative humidity in
the gymnastics center was plotted as a heat map onto a
psychrometric chart. Second, the relationship between
the occupants' reported thermal comfort and the average temperature and relative humidity measurements
in the hour prior to each response (button push event)
was plotted onto a psychrometric chart. Third, the occupants' responses and the average temperature measurements in the hour prior to each response were presented
as a box and whisker plot, which included the percentage of instances that each vote category was selected.

Results and Analysis
Figure 2 shows the temperature and relative humidity
measurements obtained during occupied hours of the
six-month study period. During occupied hours, the
average temperature was 21.2°C ± 0.9°C (70.2°F ± 1.6°F)
and the average relative humidity was 36.2% ± 17.7%. The
maximum and minimum recorded temperature during
occupied hours were 25.4°C (77.7°F) and 15.1°C (59.2°F),
respectively, while the maximum and minimum

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ASHRAE Journal - February 2020

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