Adaptive thermal comfort in university classrooms in

Building and Environment 122 (2017) 294e306

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Building and Environment journal homepage: www.elsevier.com/locate/buildenv

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 Faculty of Environmental Studies, Tokyo City University, Yokohama, Japan Interdisciplinary Graduate School of Engineering Science, Kyushu University, Fukuoka, Japan d Faculty of Mechanical Engineering, Universiti Teknologi MARA, Shah Alam, Malaysia b c

a r t i c l e i n f o

a b s t r a c t

Article history: Received 19 February 2017 Received in revised form 7 June 2017 Accepted 7 June 2017 Available online 9 June 2017

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 University, 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 Europe en de Normalisation (CEN) and American Society of Heating, mode were compatible with Comite 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.

Keywords: Thermal comfort Classrooms Air conditioning Free-running Adaptive behaviour

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 energy 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

* Corresponding author. E-mail address: [email protected] (S.A. Zaki). http://dx.doi.org/10.1016/j.buildenv.2017.06.016 0360-1323/© 2017 Elsevier Ltd. All rights reserved.

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 decisions, and occupants' well-being. As a result, more complete information about the standards that guide the design of AC systems

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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.

and associated comfort in educational buildings is needed. Previous studies have been performed in educational institutions 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 developing countries, it is necessary to understand occupants' adaptive -vis those in developed behaviour and thermal preferences vis-a 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 classroom 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.

2.2. Study buildings Three universities participated in this study: Universiti Teknologi 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 classrooms were selected in the Interdisciplinary Graduate School of Engineering Science (IGSES) buildings of KU. For reference purposes, 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 purposes; 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

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 southwest 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 €ppen world climate classifithroughout the year) based on the Ko cation of Kottek et al. [20]. Fukuoka's climate is categorized as humid subtropical, with mild winters and hot humid summers.

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

3 040 N, 101 300 E

5/3/2013e21/5/2013 (29 days)

Faculty Mechanical Engineering

FR

63 207 85 68 83 171 106

CL

CR1, CR7, CR8, CR9

A

FR CL

CA1, CA2 CA1, CA2, CA3

B

FR CL

CA4 CA4

W Isolated room W S W W W W W W W E E E N N

677

UiTM, Shah Alam

CR1 CR2 CR3 CR4 CR5 CR6 CR2, CR3, CR4, CR5, CR6

Japan

KU, Chikushi

6 530 S, 107 360 E

24/2/2013e12/3/2013 (13 days)

Total 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.

302

196 86 260

449

66 37 1428


of up to 40 students (Fig. 2c). The two buildings contained a split type air conditioning system. Despite the availability of air conditioning, these classrooms were operated on a changeover mixedmode basis, and for the purpose of this study, they were classified 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. Fig. 1. Facade of investigated buildings in: (a) Universiti Teknologi Malaysia (UTM), (b) Universiti Teknologi MARA (UiTM), and (c) Kyushu University (KU).

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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: outdoor temperature (To), indoor air temperature (Ta), indoor globe temperature (Tg), indoor air velocity (Va), and indoor relative humidity (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 temperature 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. Questionnaires were distributed before the class started and students were asked to answer questions at the end of the class. Because all respondents 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 female respondents generally having smaller bodies than male respondents. The ratio of female to male respondents was approximately even in Malaysia, while there were more male respondents in Japan (93.5%). The mean clothing insulation of


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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 Globe temperature Air movement Air movement

T&D, USA

External sensor

T&D, USA Kanomax, Japan TSI, USA

External sensor Needle probe 6542-2G Straight probe 960

0.1 C 1% RH 0.1 C 0.01 m/s 0.01 m/s

±0.5 C ±5% RH [at 25 C, 50%] ±0.3 C [20 Ce80 C] ±(2% of reading ± 0.0125) m/s [0.10e30.0 m/s] ±3% of reading

Thermo recorder TR-52i Hot-wire anemometer VelociCalc 9565

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.)

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.

298


temperature since it is used to determine comfort ranges in international standards (i.e. ASHRAE [25] and CEN [26]). 3.2. Subjective evaluations

Fig. 4. Thermo recorders and sensors attached to a stand and held 1.1 m above the floor.

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, regardless 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 velocity (