artigo

1. Adaptive thermal comfort in university classrooms in Malaysia and
Japan
Sheikh Ahmad Zaki a, *
, Siti Aisyah Damiati a
, Hom Bahadur Rijal b
, Aya Hagishima c
,
Azli Abd Razak d
a
Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia, Kuala Lumpur, Malaysia
b
Faculty of Environmental Studies, Tokyo City University, Yokohama, Japan
c
Interdisciplinary Graduate School of Engineering Science, Kyushu University, Fukuoka, Japan
d
Faculty of Mechanical Engineering, Universiti Teknologi MARA, Shah Alam, Malaysia
a r t i c l e i n f o
Article history:
Received 19 February 2017
Received in revised form
7 June 2017
Accepted 7 June 2017
Available online 9 June 2017
Keywords:
Thermal comfort
Classrooms
Air conditioning
Free-running
Adaptive behaviour
a b s t r a c t
The range of students' classroom-based activities is generally restricted; therefore, individuals have
limited options for adjusting themselves to the indoor thermal environment. This study investigated the
comfort temperature and adaptive behaviour of university students in Malaysia and Japan. Classrooms in
three universities (Universiti Teknologi Malaysia; Universiti Teknologi MARA, Malaysia; Kyushu Uni-
versity, Japan) were set to one of two conditions during the summer season: mechanical cooling (CL)
mode, where AC was switched on for cooling purposes, and free-running (FR) mode, where AC was
switched off. A total of 1428 responses were obtained. In Japan, 93.5% of the sample was male, while
more even gender distributions were found in Malaysian samples. Additionally, clo values were generally
higher amongst male respondents. In Japan, the mean comfort operative temperatures in FR mode was
found to be 25.1
C, while in Malaysia it was 25.6
C. In CL mode, mean comfort operative temperatures
were found to be 26.2
C and 25.6
C for Japan and Malaysia, respectively. Comfort temperatures in FR
mode were compatible with Comit
e Europ
een de Normalisation (CEN) and American Society of Heating,
Refrigerating and Air-Conditioning Engineers (ASHRAE) standards, while those in CL mode were mostly
within Chartered Institute of Building Services Engineers (CIBSE) guidelines. While high proportions of
students in both countries claimed that they did nothing to maintain their thermal comfort, the most
common activity observed amongst Malaysian students was changing the AC temperature setting, due to
the prevalence of CL in Malaysia.
© 2017 Elsevier Ltd. All rights reserved.
1. Introduction
Developing nations will likely consume more energy than
advanced nations by the year 2020, with buildings in tropical
countries representing major energy users [1]. Studies have shown
that in Malaysia, air conditioners (AC) account for 57% of total en-
ergy use in office buildings [2]; therefore, regulating their use has
significant potential for energy saving. In contrast, Japan has one of
the lowest electricity demand growth rates in Asia, despite having
the second highest global demand for electricity [3]. After the 2011
Fukushima Daiichi disaster and the shutdown of all 10 GW nuclear
power generators in Japan, the country has become highly
dependent on fuel imports, and particularly liquefied natural gas
(LNG), for meeting its energy needs [3]. In response to this reduced
energy generation capacity, in May 2011 the Japanese government
mandated a 15% peak power reduction for large consumers (i.e.
users requiring more than 500 kW of power) and asked small
commercial and residential consumers to follow suit [4].
Providing a comfortable and healthy microclimate is especially
essential for educational buildings, in which high environmental
quality can considerably improve occupants' learning performance
[5e7]. For the sake of practicality, thermal comfort is usually
controlled using simple design techniques, with ventilation, day
lighting, and solar control today replaced by modern AC systems;
however, the use of AC in educational buildings has complex and far
reaching design implications involving energy costs, policy de-
cisions, and occupants' well-being. As a result, more complete in-
formation about the standards that guide the design of AC systems
* Corresponding author.
E-mail address: sheikh.kl@utm.my (S.A. Zaki).
Contents lists available at ScienceDirect
Building and Environment
journal homepage: www.elsevier.com/locate/buildenv
http://dx.doi.org/10.1016/j.buildenv.2017.06.016
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Building and Environment 122 (2017) 294e306

2. and associated comfort in educational buildings is needed.
Previous studies have been performed in educational in-
stitutions at various levels, such as kindergarten [8e10], primary
school [11,12], high school [13,14], and university [15,16]. However,
each of these previous studies was unique, both in their research
method and sample characteristics. For example, in some of the
studies, ventilation modes were not defined. Meanwhile, most of
the adaptive thermal comfort studies were focused on naturally
ventilated buildings, but in reality, not many university buildings
rely on natural ventilation only. Thermal comfort analysis can be
used to identify the thermal perceptions of building occupants and
to identify possible energy savings. Using this approach in devel-
oping countries, it is necessary to understand occupants' adaptive
behaviour and thermal preferences vis-
a-vis those in developed
countries, which exhibit more environmentally friendly energy
consumption under similar climatic conditions. Malaysia shares
climatic conditions with parts of Japan [17]; however, residents
exhibit different adaptive behaviours to maintain thermal comfort
[18]. In this study, we investigated this behaviour and considered
whether or not lower energy consumption is related to factors
affecting thermal comfort. In particular, we focused on the class-
room environment, where students at all levels of education spend
most of their time [19]. The main objectives of this study were: (1)
to investigate students' comfort temperature ranges in university
classrooms in Malaysia and Japan during the summer season; (2) to
compare comfort temperatures with related standards; and (3) to
observe students' adaptive behaviour in maintaining their thermal
comfort.
2. Methodology
2.1. Climatic conditions
In Malaysia, study locations were chosen in Shah Alam and
Kuala Lumpur, both within the Klang Valley, located on the south-
west of the Malaysian peninsula. In Japan, study locations were
selected in Fukuoka, the capital of Fukuoka Prefecture, which is
located on the northern coast of Kyushu Island. The Klang Valley
experiences a tropical rainforest climate (i.e. it is hot and humid
throughout the year) based on the K€
oppen world climate classifi-
cation of Kottek et al. [20]. Fukuoka's climate is categorized as
humid subtropical, with mild winters and hot humid summers.
Surveys were conducted during the 2014 boreal summer season,
when climatic conditions were most similar in both locations. The
mean annual temperature and humidity in Malaysia are 27.0 C and
80%, respectively. During the Fukuoka summer season, mean
temperature and humidity are 26.9 C and 70%, respectively.
2.2. Study buildings
Three universities participated in this study: Universiti Tekno-
logi MARA (UiTM) Shah Alam campus and Universiti Teknologi
Malaysia (UTM) Kuala Lumpur campus in Malaysia, and Kyushu
University (KU) Chikushi campus in Japan (Table 1; Fig. 1). The
UiTM and KU campuses are located in suburban areas, while UTM is
in an urban area.
Classrooms used in this study were occupied by lecturers and
students and were picked randomly after securing the permission
of the Dean of each university faculty. In total, six classrooms in the
building of the Malaysia Japan International Institute of Technology
(MJIIT) of UTM, and 14 classrooms in the building of the Faculty of
Mechanical Engineering at UiTM were used. In Japan, four class-
rooms were selected in the Interdisciplinary Graduate School of
Engineering Science (IGSES) buildings of KU. For reference pur-
poses, the orientation of windows in each classroom that was
investigated was also recorded.
The MJIIT building in UTM is a ten-level building with two wings
to the west and east (Fig. 1a). The total area of the building is
24,200 m2
. All of the classrooms used were located in the west
wing, spread over levels two, four, seven, and eight. The area of
each classroom was approximately 57 m2
with a seating capacity
for 40 students (Fig. 2a).
The Engineering Tower building in UiTM (Fig.1b) consisted of 20
levels with a total area of 31,439 m2
. Levels nine, ten, and eleven
were chosen for use in this study. Classroom area ranged between
38 and 47 m2
and rooms were occupied by up to 30 students
(Fig. 2b). All classrooms had a similar design, including tinted
windows, fans, and an air conditioning system for cooling pur-
poses; however, some classrooms had north-west facing windows
while others had south-east facing windows.
In Kyushu University, classrooms were located in two buildings
of the Interdisciplinary Graduate School of Engineering Science
(IGSES), and were distributed on levels one and three (Fig. 1c). Each
classroom had an approximate area of 55 m2
and a seating capacity
Table 1
Summary of classrooms and sample size.
Country University, Campus Location Measurement period Building block Mode Classroom code Orientation n Total
Malaysia UTM, Kuala Lumpur 3
080
N, 101
420
E 13/4/2013e5/5/2013
(20 days)
MJIIT CL CR1 W 63 677
CR2 Isolated room 207
CR3 W 85
CR4 S 68
CR5 W 83
CR6 W 171
UiTM, Shah Alam 3
040
N, 101
300
E 5/3/2013e21/5/2013
(29 days)
Faculty
Mechanical
Engineering
FR CR2, CR3, CR4, CR5, CR6 W 106 302
W
W
CL CR1, CR7, CR8, CR9 W 196
W
Japan KU, Chikushi 6
530
S, 107
360
E 24/2/2013e12/3/2013
(13 days)
A FR CA1, CA2 E 86 449
CL CA1, CA2, CA3 E 260
E
B FR CA4 N 66
CL CA4 N 37
Total 1428
UTM: Universiti Teknologi Malaysia; UiTM: Universiti Teknologi MARA; KU: Kyushu University.
CL: Cooling; FR: free-running; n: number of votes.
E: East; N: North; W: West.
S.A. Zaki et al. / Building and Environment 122 (2017) 294e306 295

3. of up to 40 students (Fig. 2c). The two buildings contained a split
type air conditioning system. Despite the availability of air condi-
tioning, these classrooms were operated on a changeover mixed-
mode basis, and for the purpose of this study, they were classi-
fied as FR when air conditioning was not in use and CL otherwise.
Ergo, both CL and FR results in Japan come from the same set of
respondents. Some classrooms faced towards the east and were
exposed to morning sunlight, while others faced west and were
exposed to afternoon sunlight.
2.3. Data collection
Data were obtained through indoor field measurements and
questionnaire survey, which were performed simultaneously. For
each classroom, data collection was carried out at times where
students were participating in a learning activity (both morning
and afternoon). All materials, including the questionnaire, were
placed in the classroom 20 min before the lecture started. Before
data collection, students were briefed about their participation in
the survey.
2.3.1. Thermal environment assessment
Field measurements included five objective parameters: out-
door temperature (To), indoor air temperature (Ta), indoor globe
temperature (Tg), indoor air velocity (Va), and indoor relative hu-
midity (RH). For outdoor environmental parameters, data were
obtained from the MJIIT weather station and the Japan Meteorology
Agency [21]. For indoor climatic parameters (Table 2), calculation of
mean radiant temperature followed the procedures laid out in the
American Society of Heating, Refrigerating and Air-Conditioning
Engineers (ASHRAE) Handbook [22], while indoor operative tem-
perature was calculated as the mean of mean radiant temperature
(Tmrt) and Ta [23].
To investigate indoor conditions, instruments were placed at
four to five points around each classroom (Fig. 3). Each pair of
thermo recorders (TR-77Ui and TR-52i) was attached to a stand that
positioned them 1.1 m above the ground (Fig. 4). The remaining
instruments were placed in the corners of the room and measured
Ta and Tg. For each set of measurements, instruments were left for
90 min with data collected at 10 s intervals.
2.3.2. Thermal comfort survey
Questionnaires were prepared in English and accompanied by
local language translations. They were compiled based on the
works of Damiati et al. [18], Indraganti et al. [24] and Mustapa et al.
[16]. Thermal sensation was evaluated using the ASHRAE 7-point
sensation scale, 5-point scale of thermal preference, thermal
acceptability, and 6-point scale of overall comfort (Table 3).
Collected meta-data included gender, age, height and weight,
adaptive behaviour, and clothes worn by the student. Question-
naires were distributed before the class started and students were
asked to answer questions at the end of the class. Because all re-
spondents were performing the same activity, listening to lectures,
the metabolic rate is assumed to be equal to 1.2 met, based on
ASHRAE Standard 55 [25].
In total, 1428 questionnaires were completed; however, 13 were
removed owing to measurement error because the sensors were
not attached properly to the instruments (i.e. 1415 responses were
used for analysis). Respondents were all university students aged
between 20 and 23 years old (Table 4). Other physical parameters
were similar across all locations (i.e. weight, height, BMI), with fe-
male respondents generally having smaller bodies than male re-
spondents. The ratio of female to male respondents was
approximately even in Malaysia, while there were more male re-
spondents in Japan (93.5%). The mean clothing insulation of
Fig.
1.
Facade
of
investigated
buildings
in:
(a)
Universiti
Teknologi
Malaysia
(UTM),
(b)
Universiti
Teknologi
MARA
(UiTM),
and
(c)
Kyushu
University
(KU).
S.A. Zaki et al. / Building and Environment 122 (2017) 294e306
296

4. students in Japan, both female and male, is lower than that in
Malaysia. In terms of gender differences, female students in KU and
UiTM have slightly lower clothing insulation compared to male
students, and vice versa in UTM.
Fig. 2. Classroom conditions during learning activities in: (a) Universiti Teknologi Malaysia (UTM), (b) Universiti Teknologi MARA (UiTM), and (c) Kyushu University (KU).
Table 2
Specification of measurement instruments.
Instrument Parameter Manufacturer, Country Sensor type Resolution Accuracy and tolerance
Thermo recorder TR-77Ui Air temperature
Relative humidity
TD, USA External sensor 0.1
C
1% RH
±0.5
C
±5% RH [at 25
C, 50%]
Thermo recorder TR-52i Globe temperature TD, USA External sensor 0.1
C ±0.3
C [20
Ce80
C]
Hot-wire anemometer Air movement Kanomax, Japan Needle probe 6542-2G 0.01 m/s ±(2% of reading ± 0.0125) m/s [0.10e30.0 m/s]
VelociCalc 9565 Air movement TSI, USA Straight probe 960 0.01 m/s ±3% of reading
Fig. 3. Instrument layout in the classrooms of: (a) Universiti Teknologi Malaysia (UTM), (b) Universiti Teknologi MARA (UiTM), and (c) Kyushu University (KU). Cross-filled circles
denote 52i thermo recorders, triangle-filled circles denote VelociCal 9565 air movement recorders, and star-filled circles denote 77Ui thermo recorders. The positions of air
conditioners (AC; dark grey shading), fans (light grey shading), desks (blue cross-hatched areas), windows, doors, students, and lecturers are labelled. (For interpretation of the
references to colour in this figure legend, the reader is referred to the web version of this article.)
S.A. Zaki et al. / Building and Environment 122 (2017) 294e306 297

5. 3. Results and discussion
3.1. Outdoor and indoor thermal environment during the voting
The results showed that the mean outdoor temperature at the
time of measurement was much lower in Japan than in Malaysia;
however, the mean indoor air temperatures were similar, regard-
less of ventilation mode (Table 5). The results suggest that indoor
relative humidity (RH) is impacted by ventilation mode. Locations
under FR mode had higher RH than those under CL mode. The
lowest indoor relative humidity was found at UTM (Malaysia),
which was operating under CL mode, while the highest value was
observed at KU (Japan), which was operating under FR mode. In
contrast, indoor air velocity was not impacted by ventilation. In
both FR and CL mode, classrooms in Japan had the lowest air ve-
locity (0.10 m/s).
Mean values of the four thermal indices (Ta, Tg, Tmrt, and Top)
were similar for each location (i.e. 1 C difference) and all had
significant linear regressions (p 0.001) and strong correlations
(Table 6). These result confirm that any one of these indices is
suitable for analysis, and we chose to focus on operative
temperature since it is used to determine comfort ranges in inter-
national standards (i.e. ASHRAE [25] and CEN [26]).
3.2. Subjective evaluations
Questionnaire responses showed that the mean thermal
sensation vote (TSV) was within 1 TSV 1 at all locations, with
the highest value and the value closest to 0 both observed in KU
under FR mode (Table 7). The mean values at all other locations
were 0, indicating that most occupants felt cold inside the
buildings. For the 7-point TSV scale, regardless of mode (FR or CL) or
location, the highest proportion of respondents were ‘neutral,
except under CL mode in Japan (KU), where the highest proportion
(39.4%) voted for ‘slightly cool’ (Fig. 5). Most respondents preferred
‘no change’ to the indoor temperature, consistent with mean
thermal preferences (TP) that were mostly close to
0 (0.1 TP 0.1), with the exception of Japan under FR mode,
where most occupants tended to prefer warmer conditions. The
mean overall comfort (OC) ranged between 2.5 and 3.0, indicating
‘slightly comfortable’ and ‘comfortable’, respectively. The predicted
values, predicted mean vote (PMV) and predicted percentage of
dissatisfied (PPD) results are slightly different from the question-
naire results. While the mean TSV in all locations, except FR mode
in Japan, was less than zero, only students in CL mode classrooms in
Malaysia were predicted to have negative mean PMV: 0.4
and 0.3 in UTM and UiTM, respectively. This indicates that the
neutral sensations for occupants in these locations are biased to-
wards the ‘slightly cool’ side. The deviation from neutral thermal
sensation is evidenced by high PPD values compared to other lo-
cations: 14.8% and 16.1% in UTM and UiTM, respectively. The PMV
and PPD in FR mode in Malaysia, as well as both ventilation modes
in Japan, are closer to the neutral thermal sensation.
3.3. Thermal comfort zone
For indoor temperature change, Probit analysis was performed
to predict the proportion of votes for each category of the 7-point
scale [27e29]. Furthermore, this approach was used to calculate
the temperature with highest proportion of votes within TSV ±1,
Fig. 4. Thermo recorders and sensors attached to a stand and held 1.1 m above the
floor.
Table 3
Thermal comfort scales.
Thermal sensation Thermal preference Thermal acceptability Overall comfort
No. Scale No. Scale No. Scale No. Scale
3 Cold 2 Much warmer 1 Acceptable 1 Very comfortable
2 Cool 1 Slightly warmer 0 Not acceptable 2 Comfortable
1 Slightly cool 0 No change 3 Slightly comfortable
0 Neutral 1 Slightly cooler 4 Slightly uncomfortable
1 Slightly warm 2 Much cooler 5 Uncomfortable
2 Warm 6 Very uncomfortable
3 Hot
Thermal sensation 7-point scale of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE).
Table 4
Mean demographics and clothing insulation of questionnaire respondents.
University Gender Age (year) Weight (kg) Height (m) BMI (kg/m2
) Clothing insulation (clo)
UTM Female (n ¼ 111) 20 (1) 49.8 (8.9) 1.57 (0.06) 19.8 (4.2) 0.56 (0.16)
Male (n ¼ 148) 20 (1) 64.7 (16.3) 1.70 (0.08) 22.4 (4.8) 0.51 (0.18)
UiTM Female (n ¼ 135) 21 (1) 54.5 (10.9) 1.59 (0.06) 21.6 (4.2) 0.59 (0.17)
Male (n ¼ 167) 21 (1) 67.4 (17.6) 1.69 (0.07) 23.5 (5.5) 0.62 (0.20)
KU Female (n ¼ 29) 23 (1) 47.4 (4.6) 1.58 (0.05) 19.0 (1.2) 0.46 (0.12)
Male (n ¼ 420) 23 (1) 65.5 (10.6) 1.72 (0.06) 22.0 (3.3) 0.45 (0.12)
Values in brackets denote one standard deviation around the mean.
UTM: Universiti Teknologi Malaysia; UiTM: Universiti Teknologi MARA; KU: Kyushu University.
n: number of votes.
S.A. Zaki et al. / Building and Environment 122 (2017) 294e306
298

6. which was assumed to be the optimum condition for comfort.
Based on TSV, analysis was conducted using indoor operative
temperature (Top) as the covariate. The results for CL mode data
from both countries were significant to the p 0.001 level;
however, in FR mode the equations were not statistically significant
(Table 8). Mean temperatures for each equation were estimated by
dividing the constant for each TSV category with the Probit
regression coefficient [29]. Meanwhile, the standard deviation of
cumulative normal distribution was the inverse of the Probit
regression coefficient.
All equations were plotted into sigmoid curves using the func-
tion [18,29,30].
Probability ¼ CDF.NORMAL (quant, mean, S.D.) (1)
where CDF.NORMAL is the cumulative distribution function for
normal distribution and ‘quant’ is the operative temperature (C).
The results indicated that the proportion of people feeling cold
fell as temperature increased, while the proportion of those feeling
warm increased (Fig. 6a and b). By extracting the three central
points of the 7-point ASHRAE scale, the proportion of people
feeling comfortable was projected (Fig. 6c) and the function for the
curve was calculated by subtracting the Probit equations for TSV ±1
(i.e. the comfortable categories of the 7-point scale). In both
countries, the indoor operative temperature with the highest per-
centage of people feeling comfortable was ~26.0 C; although, the
Table 5
Mean values of climatic parameters.
University Mode To
(
C)
Ta
(
C)
Tg
(
C)
Tmrt
(
C)
Top
(
C)
RH
(%)
Va
(m/s)
UTM CL (n ¼ 677) 30.8 (2.4) 24.2 (0.8) 24.2 (0.9) 24.2 (1.1) 24.2 (0.9) 49.5 (6.8) 0.13 (0.11)
UiTM FR (n ¼ 106) 29.9 (3.1) 24.9 (0.3) 25.0 (0.5) 25.1 (0.9) 25.0 (0.5) 66.1 (3.0) 0.19 (0.05)
CL (n ¼ 196) 33.4 (2.9) 24.0 (1.0) 24.1 (1.0) 24.3 (0.8) 24.1 (0.9) 59.7 (6.5) 0.28 (0.09)
KU FR (n ¼ 152) 25.3 (1.6) 25.2 (0.7) 25.3 (0.7) 25.4 (0.7) 25.3 (0.7) 69.8 (5.0) 0.03 (0.02)
CL (n ¼ 284) 25.5 (2.5) 25.1 (0.8) 25.1 (0.8) 25.1 (0.8) 25.1 (0.8) 63.4 (6.7) 0.03 (0.02)
Values in brackets denote one standard deviation around the mean; To: outdoor air temperature Ta: indoor air temperature; Tg: globe temperature; Tmrt: mean radiant
temperature; Top: operative temperature; RH: indoor relative humidity; Va: air movement.
UTM: Universiti Teknologi Malaysia; UiTM: Universiti Teknologi MARA; KU: Kyushu University.
n: number of votes; CL: cooling; FR: free-running.
Table 6
Regression equations and correlation coefficients of thermal indices.
Mode Ta:Tg Ta:Tmrt Ta:Top
FR (n ¼ 258) Tg ¼ 0.97 Ta þ 0.96 (0.87) Tmrt ¼ 0.97 Ta þ 1.06 (0.65) Top ¼ 0.98 Ta þ 0.55 (0.88)
CL (n ¼ 1157) Tg ¼ 0.99 Ta þ 0.22 (0.98) Tmrt ¼ 0.99 Ta þ 0.27 (0.91) Top ¼ 0.99 Ta þ 0.26 (0.98)
Values in brackets denote correlation coefficients (r); Ta: indoor air temperature; Tg: globe temperature; Tmrt: mean radiant temperature; Top: operative temperature.
n: number of votes.
Table 7
Mean values of subjective parameters.
University Mode TSV TP PMV PPD (%) OC
UTM CL
(n ¼ 677)
0.7
(1.3)
0.0
(0.9)
0.4
(0.6)
14.8
(13.6)
3.0
(1.1)
UiTM FR
(n ¼ 106)
0.9
(0.9)
0.1
(0.8)
0.1
(0.4)
8.7
(4.3)
2.5
(0.9)
CL
(n ¼ 196)
0.9
(1.0)
0.1
(0.9)
0.3
(0.7)
16.1
(15.8)
2.7
(0.8)
KU FR
(n ¼ 152)
0.1
(1.3)
0.3
(0.7)
0.2
(0.3)
8.0
(3.9)
2.9
(1.1)
CL
(n ¼ 284)
0.6
(1.1)
0.1
(0.7)
0.1
(0.3)
7.6
(4.6)
2.8
(1.0)
Values in brackets denote one standard deviation around the mean; TSV: mean
thermal sensation vote; TP: mean thermal preferences; OC: mean overall comfort,
PMV: predicted mean vote.
UTM: Universiti Teknologi Malaysia; UiTM: Universiti Teknologi MARA; KU: Kyushu
University.
n: number of votes; CL: cooling; FR: free-running.
Fig. 5. Proportion of respondents selecting each value of thermal sensation vote (TSV) under free-running (FR; grey colour) and cooling (CL; white colour) conditions in: a) Malaysia
and b) Japan.
S.A. Zaki et al. / Building and Environment 122 (2017) 294e306 299

7. proportion was slightly higher in Japan (86%) compared with
Malaysia (80%). In both countries, approximately 70% of re-
spondents were comfortable when the temperature was between
24 and 28 C.
3.4. Comfort temperature
3.4.1. Regression analysis
Since the 1930s, regression analysis has been used to investigate
thermal comfort datasets [31]. Comfort temperature is traditionally
Table 8
Probit equations for thermal sensation vote.
Country Mode Equation Median (
C) S.D. N R2
S.E.
Malaysia CL P(3) ¼ 0.304 Top 5.85 19.3 3.293 872 0.07 0.039
P(2) ¼ 0.304 Top 6.63 21.8
P(1) ¼ 0.304 Top 7.50 24.7
P(0) ¼ 0.304 Top 8.62 28.4
P(1) ¼ 0.304 Top 9.16 30.2
P(2) ¼ 0.304 Top 9.55 31.4
Japan CL P(3) ¼ 0.444 Top 9.34 21.0 2.251 284 0.09 0.085
P(2) ¼ 0.444 Top 10.02 22.6
P(1) ¼ 0.444 Top 11.24 25.3
P(0) ¼ 0.444 Top 12.43 28.0
P(1) ¼ 0.444 Top 12.97 29.2
P(2) ¼ 0.444 Top 13.35 30.0
S.D.: standard deviation; N: number of votes; R2
: coefficient of determination; S.E.: standard error.
CL: cooling.
Top: operative temperature (
C); P(3) is the Probit of the proportion of the votes that are 3 and less; P(2) is the Probit of the proportion that are 2 and less, and so forth.
Fig. 6. Proportion of votes in each category of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 7-point scale under cooling (CL) mode in (a)
Malaysia and (b) Japan as a function of indoor operative temperature (Top). (c) Proportion of respondents considered ‘comfortable’ in Japan (circles) and Malaysia (crosses) as a
function of Top.
S.A. Zaki et al. / Building and Environment 122 (2017) 294e306
300

8. obtained by regressing the subjective TSV and indoor temperature.
In this study, linear regression was conducted using indoor oper-
ative temperature as the independent variable and the 7-point TSV
ASHRAE scale as the dependent variable (Fig. 7). Predicted mean
vote (PMV) was calculated for each set of data based on six pa-
rameters: Ta, Tmrt, Va, RH, metabolic rate, and clothing insulation,
using the PMV calculator plugin for excel by Tanabe and Sato [32].
Under CL mode, regression equations for both countries were
found to be significant at the p 0.001 level, despite low R2
values;
however, regression equations were not statistically significant
under FR mode, for which too few samples were available (Table 9).
The slope of the regression line was 0.332 units/C in Malaysia and
0.424 units/C in Japan, with the change in temperature per point of
TSV found to be 3.0 C and 2.3 C, respectively. The neutral tem-
peratures acquired were 26.5 C and 26.3 C for Malaysia and Japan,
respectively.
3.4.2. Griffiths' method
As regression analysis was only possible for data collected under
CL mode, the Griffiths' method [33] was also used to estimate the
comfort temperatures in all locations. This approach was suitable
for use with both CL and FR because it can be used to calculate
neutral temperatures from small numbers of samples using a pre-
sumed constant as the rate of temperature change per point of
sensation scale. Comfort temperatures using the Griffiths' method
were calculated using the expression:
Tc ¼ T þ (0 TSV)/a (2)
where Tcomf is the comfort temperature (C), T is temperature (C),
and a indicates Griffiths' constant.
For a, we tested three different constant values (0.25, 0.33, and
0.50), as previously employed by Nicol et al. [34], Rijal et al. [35],
and Mustapa et al. [16], respectively. For most locations, the mean
comfort temperatures calculated using these values were higher
when a smaller constant was used (Table 10), with the exception of
data collected under FR mode in Japan. Given the similar climatic
conditions in Japan and Malaysia at the time of the study, the range
of measured indoor operative temperatures was relatively narrow.
Using 0.25 and 0.33 as a, comfort temperatures were least consis-
tent with the measured range. On this basis, we concluded that 0.50
was the most appropriate coefficient. This is in line with the study
of Nicol and Humphreys [36], who found that the actual value of the
constant must be 0.40.
The results also showed that mean temperatures based on the
three conditions were almost identical for each location (Table 11).
Furthermore, estimated comfort temperatures using a Griffiths'
constant of 0.50 resulted in values closest to neutral temperatures.
Using 0.50 as the Griffiths' constant, the mean comfort operative
temperature under FR mode in Japan (25.1 C) was lower than that
in Malaysia (26.8 C). In contrast, students under CL mode in Japan
had a mean higher comfort temperature (26.2 C) than those in
Malaysia (25.6 C). These results could mean that Japanese students
are more sensitive to thermal changes caused by different venti-
lation modes operated during the summer; however, the differ-
ences are very small (1 C) and may not be significant. This gap
could be affected by the insulation of clothing worn by students in
Japan, which was considerably lower than that of clothes worn by
students in Malaysia (see Table 7). Additionally, it might also be
caused by the fact that the Japanese sample was predominantly
male, compared to the Malaysian sample, in which the numbers of
students of each gender were almost equal. This supports findings
Fig. 7. Linear regression (solid black line) through thermal sensation vote (TSV) vs. indoor operative temperature (Top) under cooling (CL) mode in (a) Malaysia and (b) Japan. Dashed
black line denotes the predicted mean vote (PMV).
Table 9
Regression equations under cooling (CL) mode.
Country Mode Equation n R2
S.E. p
Malaysia CL TSV ¼ 0.332Top 8.8 872 0.06 0.044 0.001
Japan CL TSV ¼ 0.426Top 11.2 284 0.09 0.083 0.001
n: number of votes; R2
: coefficient of determination; S.D.: standard deviation; S.E.:
standard error, p: significance level.
TSV: thermal sensation vote; Top: indoor operative temperature.
Table 10
Comfort operative temperatures based on the Griffiths' method.
Country Mode n a ¼ 0.25 a ¼ 0.33 a ¼ 0.50
Malaysia FR 106 28.6 (3.7) 27.7 (2.8) 26.8 (1.9)
CL 872 27.0 (4.7) 26.4 (3.6) 25.6 (2.4)
Japan FR 152 24.9 (5.1) 25.0 (3.9) 25.1 (2.6)
CL 284 27.3 (4.3) 26.8 (3.2) 26.2 (2.1)
Values in brackets denote one standard deviation around the mean; a: Griffiths'
constant value employed.
FR: free-running, CL: cooling.
n: number of votes.
S.A. Zaki et al. / Building and Environment 122 (2017) 294e306 301

9. from previous studies [37e39], that gender differences could affect
thermal sensation.
While students in Malaysia showed predictable results: higher
comfort temperature in FR mode compared to CL mode, students in
Japan have reversed results. During summer season, Japanese
government recommends the temperature setting for cooling at
28 C [40]. Generally, buildings with FR mode have low tempera-
ture condition and people find that temperature is comfortable.
Meanwhile in CL mode, people set high temperature based on the
government's suggestion and people find that temperature is
comfortable. These results were concluded in several studies in
Japan, based on field survey during summer season in offices [16],
[30] [41], as well as houses [29], [42].
The results could also indicate that students in Malaysia are
acclimatized to their environment, allowing those under FR mode
to be comfortable at higher temperatures and vice versa. Compared
with the other three thermal indices (Tci, Tcg, and Tcmrt), mean
comfort operative temperature was similar for all locations (Fig. 8).
For all of these results, it is important to note that the students in
the KU classrooms with different ventilation modes were the same
group of people, since the buildings employed changeover mixed-
mode ventilation [43]. In contrast, classrooms in Malaysia were
designed to use either FR or CL mode, meaning that the re-
spondents for each ventilation mode were different groups of
people.
Previous studies of thermal comfort in classrooms have shown
Fig. 8. Comfort operative temperatures for different thermal indices based on a Griffiths' constant value (a) of 0.50 in (a) Malaysia under cooling (CL) and free-running (FR) mode,
and in (b) Japan under the CL and FR modes.
Table 12
Comfort temperatures from different studies.
Ref. Year Country Mode Sample size To (
C) Thermal index Tcomf (
C)
[45] 1998 Hawaii, USA FR 1052 24.0e33.0 Top 27.4
[14] 2003 Singapore FR 506 26.2e30.0 Top 28.8
[44] 2006 Taiwan FR 362 23.1e30.5a
Top 26.2
[15] 2014 India FR 121 14.5e33.0 Top 26.5
[16] 2016 Japan FR 81 3.5 28.0 3.6 Tg 26.7 (1.9)
Current study Malaysia FR 106 29.9 Top 26.8 (1.9)
Current study Japan FR 152 25.3 Top 25.1 (2.6)
[45] 1998 Hawaii, USA CL 703 24.0e33.0 Top 26.8
[44] 2006 Taiwan CL 932 23.1e30.5a
Top 25.6
[46] 2011 China CL 82 24.5e30.0 Top 26.8
[47] 2015 Indonesia CL 90 3.7 25.6e32.9 3.8 Ta 24.9
[18] 2016 Malaysia CL 1114 31.2 Top 25.6 (2.2)
[16] 2016 Japan CL 222 3.9 28.0 3.10 Tg 26.6 (1.6)
Current study Malaysia CL 872 31.4 Top 25.6 (2.4)
Current study Japan CL 297 25.4 Top 26.2 (2.1)
FR: free-running; CL: cooling.
To: outdoor air temperature.
Top: indoor operative temperature; Ta: indoor air temperature; Tg: indoor globe temperature.
Tcomf: comfort temperature; values in brackets denote one standard deviation around the mean.
a
Temperature obtained from http://www.weatherbase.com/.
Table 11
Mean temperatures for selected TSV, TP, and OC.
Country Mode TSV ¼ 0 TP ¼ 0 OC 3
Malaysia FR n ¼ 39 25.0 (0.4) n ¼ 67 25.0 (0.4) n ¼ 60 25.1 (0.5)
CL n ¼ 288 24.4 (0.9) n ¼ 454 24.3 (0.9) n ¼ 174 24.1 (0.9)
Japan FR n ¼ 61 25.4 (0.8) n ¼ 83 25.3 (0.7) n ¼ 59 25.3 (0.7)
CL n ¼ 101 25.3 (0.7) n ¼ 166 25.1 (0.7) n ¼ 117 25.1 (0.7)
TSV: thermal sensation vote, TP: thermal preference, OC: overall comfort; values in brackets denote one standard deviation around the mean; n: number of votes.
FR: free-running, CL: cooling.
S.A. Zaki et al. / Building and Environment 122 (2017) 294e306
302

10. various results. In both tropical climates and in temperate climates
during the summer season, most comfort temperatures have been
found to be high (Table 12). In the current study, the comfort
temperatures of students under FR mode in Malaysia were found to
be slightly higher than those in university classrooms in Taiwan
[44] and India [15]. In contrast, studies in primary schools in Hawaii
[45] and Singapore [14] have shown even higher results (although
the latter study combined the comfort temperatures of students
and teachers). Postgraduate students in Fukuoka [16] were also
found to have a higher comfort temperature compared with the
Japanese students in this study who were under FR mode.
The comfort temperature of students under CL mode in Malaysia
was identical with the results of previous studies of postgraduate
students in Malaysia [18], as well as of university classrooms in
Taiwan [44]. Other studies in tropical countries showed various
results, including lower comfort temperatures in university class-
rooms in Indonesia [47], and higher ones in primary school class-
rooms in Hawaii [45]. Similarly, the comfort temperature found in
this study for Japanese students under CL mode was similar to the
results from postgraduate students in Japan [16]. A study based in
China under a temperate climate during summer season resulted in
a slightly higher comfort temperature (26.8 C) [46].
3.5. Comparison with standards
The comfort temperatures in each location were also compared
to adaptive models from existing standards, including Comit
e
Europ
een de Normalisation (CEN) Standard EN15251 [26] and
ASHRAE Standard-55 [25] for FR mode, and the Chartered Institute
of Building Services Engineers (CIBSE) guide [48] for CL mode
(Fig. 9). All of these standards have thermal comfort models based
on outdoor temperatures. The CEN Standard EN15251 and the
CIBSE guide use running mean outdoor air temperature (Trm),
which is the weighted mean of outdoor air temperatures of seven
sequential days prior to the day of survey [26]. The ASHRAE
Standard-55 uses monthly mean outdoor air temperature (Tom),
which is calculated from mean daily outdoor air temperatures (Tod)
for all days in each month [25]. The ASHRAE standard (2004) [49] is
Fig. 9. Comparison of the results with existing standards: a) Comit
e Europ
een de Normalisation (CEN) Standard EN15251, b) American Society of Heating, Refrigerating and Air-
Conditioning Engineers (ASHRAE) Standard-55, and c) the Chartered Institute of Building Services Engineers (CIBSE) guide. Filled circles denote data from Malaysia, while open
circles denote data from Japan. Black dashed lines denote the upper and lower limits of the corresponding standard. Recommended temperature settings based on local regulations
in each country are illustrated using horizontal lines (continuous grey line for Japan and dash-dot grey line for Malaysia).
S.A. Zaki et al. / Building and Environment 122 (2017) 294e306 303

11. based on the monthly mean outdoor temperature. The modified
ASHRAE standard (2013) [25] indicated the prevailing mean out-
door temperature, which is based on mean daily outdoor air tem-
peratures. However, the regression coefficient and constant are the
same for the original and revised version of the standard [25,50,51].
The results from FR mode were consistent with both relevant
standards (Fig. 9a and b); however, more points fell within the
highest comfort zone category of the ASHRAE standard than in that
of the CEN standard. While most of the comfort temperature results
from Malaysia and Japan were within category I of the CEN adaptive
thermal comfort model, some points fell below the lower limit
(Fig. 9a). In contrast, all students' comfort temperatures under FR
mode in Malaysia were compatible with the ASHRAE standard's
90% acceptability level. Only one point from the FR mode in Japan
was situated between the upper limits of acceptability (80% and
90%; Fig. 9b). Most results from under CL mode in both countries
were situated within the CIBSE guide comfort zone (Fig. 9c). Since
the classrooms in Japan are situated in change-over mixed mode
building, the data from both FR and CL modes were also combined
and compared with both ASHRAE and CEN standards as shown in
Fig. 10 a and b.
3.6. Adaptive behaviour
Thermal comfort is greatly affected by adaptation. In this study,
students were asked to declare any adaptive action they had un-
dertaken to adjust to the indoor thermal condition in the class-
room. Under both FR and CL ventilation modes, most students in
Japan did nothing to adapt themselves because lectures lasted only
90 min. The most common adaptive activity in Japan was drinking
water or juice (15%), perhaps reflecting the easiest way for students
to respond to the existing thermal environment without inter-
rupting learning activities (Fig. 11). While there could be other
reasons for students to be consuming beverages, the questionnaire
specifically asked them to choose any activities they did in order to
overcome thermal discomfort. In Malaysia, the most common ac-
tion was changing the temperature setting of the AC (27%), which
was more popular than ‘did nothing’. This is in line with the results
of previous studies in Malaysia, Indonesia, and Japan, which found
that office building occupants in Malaysia tended to use AC systems
more than those in the other two countries [18]. Another study in
Chongqing [52] found that respondents under FR mode in class-
rooms tended toward other behavioural adaptations (e.g. adjusting
clothes, operating ceiling fans, and consuming beverages). These
results are also in agreement with a similar study conducted in
Fukuoka [16], where most students under CL mode declared that
they ‘did nothing’ to adapt, while students under FR mode tended
to overcome thermal discomfort by drinking water, switching on
fans, and/or opening windows and doors. Therefore, these results
show that in less energy intensive environments, such as FR mode
Fig. 10. Comparison of results from change-over mixed mode ventilation in Japan, with a) CEN standard, and b) ASHRAE standard.
Fig. 11. Adaptive actions taken by survey participants to alter their thermal environment in: a) Malaysia and b) Japan.
S.A. Zaki et al. / Building and Environment 122 (2017) 294e306
304

12. in Japan, more adaptive actions are taken by occupants to remain
thermally comfortable. Conversely, by encouraging active partici-
pation by occupants in maintaining their thermal comfort, it is
possible to encourage energy savings from reduced HVAC use.
4. Conclusions
In this study, thermal comfort in university classrooms in
Malaysia and Japan was investigated. Based on the results, a
number of conclusions were drawn. While 70% of respondents
voted within the three central TSV points, within the comfortable
range, those who admitted to feeling thermally uncomfortable
were usually cold, except in FR mode in Japan. This points to some
degree of overcooling in university classrooms in the locations
investigated, which is endemic to other mechanically cooled loca-
tions investigated in Malaysia and Japan, both in classrooms and
workplaces.
Using the data from this study, it was calculated that mean
comfort temperatures under FR and CL mode were 26.8 C and
25.6 C in Malaysia, and 25.1 C and 26.2 C in Japan, respectively.
These results are consistent with those from previous studies in
Malaysia and Japan and show that comfort temperatures could be
affected by geographical factors. However, other factors such as
gender characteristics and clothing insulation might be affecting
this result, due to the dominance of male respondents in the sample
in Japan and higher insulation of clothing worn by respondents in
Malaysia. Additionally, results from FR mode in Malaysia and Japan
were compatible with both CEN and ASHRAE standards. This shows
that it is possible to apply these standards in hot-humid climates,
despite having been developed for temperate climates.
Most comfort temperature results from CL mode in Malaysia
and Japan were within the CIBSE comfort zone guidelines, but a
number of points from both countries fell above the upper limit.
This might point to overcooling when using existing guidelines,
which could contribute to excessive energy consumption. Addi-
tionally, the current guideline for HVAC buildings might also un-
derestimate occupants' thermal preference in hot-humid climates,
where a greater degree of heat tolerance could be found in the
general population.
Most respondents in this study did not perform any thermal
adaptations over the observation period. However, the majority of
positive responses were from CL mode in Malaysia, where the
highest proportion of students reported adjusting AC systems to
alter their thermal environment. This is mainly due to both the
widespread availability of AC, the ease and effectiveness of this
adaptation method, and the fact that the students themselves are
not responsible for the bills incurred for AC use.
Funding
This research was supported by a Grant-in-Aid from the AUN/
SEED Net Collaborative Research Program (grant number 4B155) of
the Japan International Cooperation Agency (JICA), a matching
grant (grant number 00M44), and a research university grant (grant
number 11H67) from the Universiti Teknologi Malaysia.
Acknowledgements
We would like to thank all participants in the survey, as well as
the management and staff of the Universiti Teknologi Malaysia,
Universiti Teknologi MARA, and Kyushu University. Our sincere
appreciation is extended to Nur Atikah Shaari for her huge contri-
bution to data collection and Norakmal Affif Norizan for his help
during data processing.
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