Recent Advances in Energy, Environment and Development
Thermal Comfort Assessment of a Classroom in Tropical Climate
Conditions
KHADIJAH KAMARUZZAMAN1 and AZIMIN SAMSUL BIN MOHD TAZILAN1,2
1
Department of Architecture
Faculty of Engineering and Build Environment
Universiti Kebangsaan Malaysia,
43600, Bangi, Selangor.
MALAYSIA
2
Solar Energy Research Institute
Universiti Kebangsaan Malaysia,
43600, Bangi, Selangor.
MALAYSIA
[email protected], [email protected]
Abstract: - Thermal comfort is the study of indoor comfort level feel by the occupant in a room. This paper
presents the study of thermal comfort that had been carried out in a classroom on the second floor at a local
school in Bandar Baru Bangi, Selangor, Malaysia. The study was made in 5 days from 2 pm to 6 pm. This
study was carried out to assess their thermal conditions during the students’ lesson hours. Thermal comfort
variables were measured during lesson hours too. Objective data analysis showed that none of the classes had
thermal conditions falling within the comfort zone of ASHRAE standard 55. The result shows the
environmental condition of the class is warm to hot in 7-point ASHRAE scale. The linear regression between
Predicted Mean Vote and Operative Temperature reveals that the maximum acceptable temperature in this field
of study is 26.5ºC.
Key-Words: - Thermal Comfort, Field Study, PMV. PPD, Classroom, Tropical Climate
physical work activity done in classroom, mean
radiant temperature, such as radiant temperature of
the walls, floor, windows and so on. The mean
radiant temperature is a significant factor, especially
in buildings whose envelopes were exposed to a
strong solar radiation. Cold walls or windows may
cause a person to feel cold even though the
surrounding air may be at a comfortable level.
Likewise, warm surfaces may cause a person to feel
warmer than the surrounding air temperature would
indicate.
Several studies in the tropics have been
conducted by various researchers using the
Malaysian climate conditions as case studies. A
field study on the environmental conditions and
occupant comfort was carried out in two schools,
which is a primary and secondary school, and in a
public waiting area in a health clinic in Johor Bahru,
located in the southern region of Malaysia showed
that more than 80% of the respondents found that
their indoor thermal conditions acceptable even
though the thermal sensation votes (TSV) exceeded
those specified by ASHRAE Standard 55 and the
environmental assessments exceeded the standard.
1 Introduction
Thermal comfort is defined by ASHRAE as ‘that
condition of mind which expresses satisfaction with
the thermal environment and is assessed by
subjective evaluation” [1]. The subjective evaluation
of thermal comfort is influenced by the thermal
environment and personal factors influencing the
heat transfer with this environment, but also by
psychological factors influencing the condition of
mind directly [2]. All these factors in thermal
comfort can be altered by behavioral, physiological
or psychological adaptation. Thermal comfort is a
key component of quality of indoor environments
and environmental elements such as heat from
electrical lighting, lack of adequate ventilation, high
humidity levels, and poorly performing building
envelopes can contribute to poor thermal comfort.
Previous studies indicated that thermal comfort
does affect the productivity and learning [3 - 10]. A
student’s perception of thermal comfort is affected
by air temperature in classroom, air movement or
velocity in the classroom, humidity in classroom,
the clothing they worn to lecture, amount of
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Recent Advances in Energy, Environment and Development
The neutral temperature and comfort range were
obtained through linear regression analysis of TSV
and in the Fanger's PMV model [11]. From the
subjective assessment, it was found that the
occupants can accept the thermal range beyond the
ASHRAE comfort zon indicated that the occupants
in the tropic environment such as Malaysia have a
higher heat tolerance and can adapt to the
environment [11].
Another study has been conducted to evaluate
the comfort level of an air-conditioned classroom at
the School of Manufacturing Engineering campus
using objective measurement, subjective assessment
[12]. The results obtained showed that measured
temperature and relative humidity were within the
standard comfort condition by ISO EN7730 (1994)
while air velocity exceeded the standard limit by
ISO EN7730 (1994). The overall comfort vote,
Predicted Mean Vote (PMV) and Predicted
Percentage Dissatisfied (PPD) indices shows that
occupants are comfortable and satisfied with the
classroom comfort level [12].
The primary objectives of this study is to explore
the indoor climate in mechanically ventilated
buildings in Malaysia such as in classrooms of
schools and to investigate occupants level of indoor
thermal comfort in a tropical region. This paper
reports the procedures, data and results obtained
from this study.
2.2 Data collection
The physical data for the indoor environment of the
classroom were measured by the Thermal Comfort
Equipment as shown in Fig. 2. This equipment can
measure ambient temperature, air velocity, radiant
men temperature, relative humidity, noise,
illuminating and CO2. Fig. 2 shows the equipment
designed by the Solar Energy Research Institute
(SERI).
Fig. 2. Thermal comfort equipment in class 2 Lili
2.3 Clothing insulation value and activity
rate.
Clothing insulation is the thermal insulation
provided by clothing. The insulation of clothes are
often measured with the unit "Clo", where 1 Clo =
0.155 m2K/W. Based on the ASHRAE Standard 55,
there is a method for estimating the personal
parameters. By observing the occupants in the class,
the clothing and metabolic rate were estimated
based on the observation made during the survey.
Table 1 shows estimated clothing insulation value
and activity rate for class 2 Lili students. It is
compulsory to all students in this school to wear the
school uniform which were white sleeve shirts and
straight long dark blue trousers for male, and dark
blue pinafore or ‘baju kurung’ (light blouse) and
dark blue a-line skirts and hijab for female. Fig. 3
illustrates the standard school uniform in Malaysia.
2 Methodology
2.1 Field study description
Sekolah Kebangsaan Jalan 3 was opened on the first
of July in 1995. Located about 10 km from Bandar
Kajang, the total gross area of this school is 4.75
acres or 38,000 square meters. The school name was
taken from where the school site is located which is
in a residential area of Section 3, Bandar Baru
Bangi. Currently there are 55 classes, 1969 students,
95 teachers and 8 employees in this school. Fig. 1
shows the location map of SK Jalan 3.
Table 1. Estimated clothing insulation value and
activity rate
Clo Met
Estimated value baesd on ASHRAE 0.6 1.3
Fig. 1. Location map of SK Jalan 3.
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Recent Advances in Energy, Environment and Development
Fig. 3. Standard school uniform in Malaysia
3 Classroom setup
The field study was carried out for a week from
Monday, May 7th 2012 to Friday, May 11th 2012 the
equipment was setup in class 2 Lily that was located
on the second floor. The classroom is located on a
3-storey building and the building was also designed
for naturally ventilation and each classroom is also
mechanically ventilated by three ceiling fans. The
measuring instruments were read at about 1 meter
above the floor level and were set at the back of the
class in order to prevent from disturbing the pupils
in class. The structure, design and measurement of
all classes in block C are the same. This also applies
to the types of furniture inside the classrooms. Each
class is equipped with wooden tables and chairs.
However, the amount and arrangement of furniture
in each class are different. Fig. 4 shows the students
in class 2 Lili located on the second floor of block
C. Fig. 5 shows the layout plan of classroom and
location of the Thermal Comfort equipment.
Fig. 5. Layout plan of class 2 Lili
4 Results and discussions
The environmental data was collected for about 5 to
6 hours a day for 5 days straight. Fig. 6 represents
the calculated Predicted Mean Vote (PMV) from
2pm to 6pm over 5 days in a week. The PMV in all
days were above 2.
Fig. 6 Predicted mean vote for 5 days
Fig. 7 illustrates calculated PMV versus Percentage
of Predicted Dissatisfied (PPD). According to 7point ASHRAE scale, the environment of the
classroom is from “warm” to “hot” while 80% to
100% of occupants feel dissatisfied.
Fig. 4. Field study in class 2 Lili
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Recent Advances in Energy, Environment and Development
References:
[1] ASHRAE
Standard
55-2004,
Thermal
environmental
conditions
for
human
occupancy, American Society of Heating,
Refrigerating
and
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Engineers,2004.
[2] P. O. Fanger, Thermal Comfort. Analysis and
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[3] J. Van Hoof, M. Mazej, J. L. M. Hensen,
Thermal comfort: Research and practice,
Frontiers in Bioscience, Vol. 15, No. 2, 2010,
pp. 765-788.
[4] EN ISO 7730:2005 Ergonomics of the Thermal
Environment - Analytical Determination and
Interpretation of Thermal Comfort Using
Calculation of the PMV and PPD Indices and
Local Thermal Comfort Criteria, ISO
International Standardisation Organisation
Geneva, 2005.
[5] ANSI/ASHRAE Standard 55 - Thermal
Environmental
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for
Human
Occupancy ASHRAE American Society of
Heating, Refrigerating and Air-Conditioning
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[6] EN 15251:2007 Indoor Environmental Input
Parameters for Design and Assessment of
Energy Performance of Buildings Addressing
Indoor Air Quality, Thermal Environment,
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[8] Z. Li and J. Yao, An investigation of thermal
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Fig. 7. PPD versus PMV
Fig. 8 shows the trend of PMV versus Operative
Temperature (OP). The maximum acceptable
temperature is 26.5ºC where the PMV is 1.
Fig. 8. PMV trend versus OP for 5 Days
5 Conclusions
According to the direct measurement of thermal
comfort at classrooms, most classrooms do not
provide a thermal comfort environment and
satisfaction for teachers and students. The study
field concludes that the environment of class 2 Lili
is from “warm” to “hot” in 7-point ASHRAE scale.
Hence, the improvements of thermal environment at
this classroom have to be carried out. The air
ventilation systems of the classroom have to be
improved. Based on the layout plan of the class, the
seats in of classroom also have to be modified. Due
to over capacity of pupils, the arrangement of desk
and chairs are too close together. It is recommended
that the class only have around 30 pupils per class.
Human body provides heat transfer or heat loss. If
the seats are too close or too near with each other,
the pupils will feel more discomfort or hot.
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[12] Z. A. Zailani, R. Hamidon, M. S. Hussin, M. F.
M. A. Hamzas and H. Hadi, 2012, Classroom
comfort ability assessment: A case study,
International
Review
of
Mechanical
Engineering, Vol. 6, No. 3, 2012, pp. 339-345.
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