Subjective Perception of Thermal Comfort Study in Air-conditioned University Laboratories Academic research paper on "Economics and business"

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ScienceDirect

Procedia - Social and Behavioral Sciences 91 (2013) 192 - 200

PSU-USM International Conference on Humanities and Social Sciences

Subjective Perception of Thermal Comfort Study in Air-Conditioned University Laboratories

Hussin M1,2*

1School of Housing, Building and Planning, Universiti Sains Malaysia, 11800 USM,Penang, Malaysia 2Development Department, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia (*corresponding author; email: hussinm@usm.my; Tel. No.:604-6533301; Faks No: 604-6587688)

M. R Ismail1, M. S. Ahmad2

1School of Housing, Building and Planning, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia Development Department, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia

Abstract

Thermal comfort is the condition of mind that expresses satisfaction with complex thermal factors. There are three main factors that can affect the human comfort, which must be considered by engineers before designing air-conditioning systems; effective temperature, relative humidity and air motion. Present study aims to investigate on the environmental conditions and occupants comfort in teaching and learning laboratories in Engineering Campus and Main Campus of Universiti Sains Malaysia. A study was carried out in order to identify differences in the perception of thermal comfort of laboratory staffs in centralized air-conditioned and 'split-unit' type of air-conditioned laboratories used in Engineering Campus and Main Campus, respectively. American Society of Heating, Refrigerating and Air-conditioning Engineer (ASHRAE) [1] 7-points scale of thermal sensation was used to evaluate thermal sensation of the laboratory occupants. Based on the occupants' perception towards the scale, generally 75% and 55% of the respondents in Main Campus and Engineering Campus respectively voted within the central three categories of thermal acceptibility (-1, 0, 1). Besides that, based on 5-Likert scale on general comfort, 85% and 87% of the respondents from Main Campus and Engineering Campus respectively found to be satisfied with their laboratory environment

Corresponding author; email: hussinm@usm.my; Tel. No.:604-6533301; Faks No: 604-6587688

1877-0428 © 2013 The Authors. Published by Elsevier Ltd.

Selection and peer-review under responsibility of Universiti Sains Malaysia.

doi: 10.1016/j.sbspro.2013.08.417

© 2013TheAuthors. Publishedby Elsevier Ltd.

Selectionand peer-review under responsibility of Universiti Sains Malaysia. Keywordsithermal comfort; laboratory;thermal sensation;air-conditioning type

1. Introduction

Air-conditioned office buildings aims to provide a thermally acceptable environment for human comfort and work that would in turn enable better work productivity and less thermal dissatisfaction [1, 2]. This is the paramount important for buildings in the tropics where air-conditioning of the indoor environment is not uncommon. The first scientific studies about the effect of the thermal environment quality in classrooms on the students' performances began around the middle of 1950. An interesting review of the results of these first studies, lots of them performed as field studies, is given in the work of Pepler and Warner [3]. After this period, the birth of the Fanger theory about thermal comfort based on the results from a fully controlled climate chamber, broke the developing of new field researches on thermal comfort [4]. But the growing interest in the last years about the adaptive theory of thermal comfort has again stimulated researches by field studies aimed at qualifying the thermal environment both objectively (by measurements) and subjectively (by occupants judgements).

Previously, due to the adverse effect of indoor air quality (IAQ), reports on various researches have continued rising, particularly in residences and offices, only in last few years, few studies are concerned with the indoor environment of school buildings [5, 6]. However, there is still very little work reported on classrooms occupied by adult students. Good IAQ in university provide a conducive environment for teaching and learning activities. In a research carried out by Awbi and Pay [5] in the university classrooms which have different capacities, it was reported that the IAQ during occupancy periods were very poor. By means of the basic space and function of educational buildings where teaching and learning are the priority, problems with the IAQ in classrooms are seen to be at risk. In university, many students spend most of their time in classroom, libraries, laboratories, hostels and other indoor environments. Thus giving rise to the need for research into the indoor thermal environment in institutional building. This research is crucial since study has shown that IAQ has a noticeable effect on the intellectual efficiency and the health of the users [7].

This paper attempts to evaluate the thermal comfort in a laboratory by employing subjective assessment. A questionnaire survey (according to ASHRAE 7-Points Scale [1]) was administered to the occupants to determine their thermal comfort sensations and investigate their perception of the degree of comforts in the laboratory.

1.1. Methodology

Subjective Assessment-Questionnaire Surveys

A subjective assessment in the form of a questionnaire survey was undertaken, and 62 respondents which are the technical staffs in the three Engineering Schools became the subject of the survey. In the main campus, 176 respondents from six Science based Schools are involved in this subjective assessment. Laboratories in Engineering Campus and Main Campus used centralized air-conditioned and 'split-unit' type of air-conditioned, respectively. The assessment of the thermal environment was based on the occupants' vote on the thermal sensation and impressions of comfort with regard to air temperature, relative humidity and air movement.

The questionnaire survey based on ASHRAE 7-Points Scale was used in this subjective measurement. Data from the surveys was analysed using statistical package for social science (SPSS).

1.2 Results and Discussio

Figure 1 shows the subjective responses to temperature (thermal comfort), ranged from -3 (cold) to +3 (hot). The results show that the 75% of the respondents from Main Campus voted -1 (slightly cool), 0 (neutral) and -1 (slightly warm) sensation. While for Engineering Campus, most of the votes ranged -2 (cool) to 0 (neutral) which consists of 65% of the 62 respondents. The ASHRAE Standard 55-2004 [1] specified that an acceptable thermal environment should have 80% of occupants vote for the central three categories (-1, 0, 1). In this study, only 75% from Main Campus and 55% from Engineering Campus voted within the central three categories showing that laboratories in both campuses were not in thermal acceptable condition. Occupants' perception of the thermal acceptability is shown in Figure 2. It is observed that 80% and 85% of the occupants in Main Campus and Engineering Campus appear to be satisfied with the thermal conditions in the laboratories, respectively. Figure 3 exhibits the distribution percentage of subjective judgement on thermal preference. It can be seen that 60% respondents from Main Campus and 69% respondents from Engineering Campus preferred with the existing environment. While 34% and 26% of the occupants in Main Campus and Enginering Campus want to be coller, respectively. Distribution percentage of subjective judgement on satisfaction of thermal environment is shown in Figure 4. It is clearly shown that 68% respondents from Main Campus and 73% respondents from Engineering Campus satisfied with their laboratory thermal environment.

Figure 5 shows the distribution percentage of subjective judgement on acceptability of air movement. Results indicate that in Main Campus 69% accept the air movement in the laboratories, whereas 31% of the occupants are not satisfied with the air movement condition. While in Engineering Campus, 77% accept the air movement in the laboratories, whereas 23% of the occupants are not satisfied with the air movement condition. Figure 6 exhibits the distribution percentage of subjective judgement on air movement preference. It is apparent that 77% of the respondent in Main Campus preferred to have more air movement in the laboratories, eventhough the current air movement is acceptable for them. While in Engineering Campus, 74% of the respondent prefered to have more air movement in their laboratories. The subjective responses on humidity are presented in Figure 7. It was observed that for the overall votes, the occupants in Main Campus and Engineering Campus were comfortable with the relative humidity, with 81% and 89% voted for acceptable range, respectively. Based on distribution percentage of subjective judgement on humidity preference in Figure 8, it is observed that in Main Campus 59% of the respondent prefer to maintain the relative humidity, whereas 27% prefer to have more moisture in the air and 14% want dried air in the laboratories. Slightly similar trend was observed in the Engineering Campus. Distribution percentage of subjective judgement on general comfort is shown in Figure 9. The distribution of subjective responses on overall thermal comfort showed that 85% and 87% respondents in Main Campus and Enginering Campus voted in the neutral and comfortable categories, respectively. However in the Main Campus, 14% of the respondents voted uncomfortable scale.

Fig. 1. Distribution percentage of subjective judgement on thermal comfort

g 60 <u _

20 10 0

□ Main Campus □ Engineering Campus 85

-- 20

-- 15

-- i i

acceptable not acceptable

Thermal Acceptability

Fig. 2. Distribution percentage of subjective judgement on thermal acceptability

Fig. 3. Distribution percentage of subjective judgement on thermal preference

Fig. 4. Distribution percentage of subjective judgement on satisfaction of thermal environment

Fig. 5. Distribution percentage of subjective judgement on acceptability of air movement

Fig. 6. Distribution percentage of subjective judgement on air movement preference

Fig. 7. Distribution percentage of subjective judgement on acceptability of humidity

Fig.8. Distribution percentage of subjective judgement on humidity preference

Fig. 9. Distribution percentage of subjective judgement on general comfort

1.3 Conclusions

Based on the subjective assessment, following conclusions can be made:

• The results show that 75% of the respondents from Main Campus and 55% from Engineering Campus voted within the central three categories (-1, 0, 1). Based on ASHRAE Standard 55-2004, this showed that the laboratories in both campuses were not in thermal acceptable condition. However 80% and 85% of the occupants in Main Campus and Enginering Campus accepted the thermal conditions in their laboratories, respectively.

• The overall comfort vote indicate that the occupants are satisfied with the general comfort and 85 and 87% of the respondents from Main Campus and Engineering Campus voted to be in the range of '0' (neutral) and '+1 (comfortable), respectively.

• Based on subjective assessment, it is found that centralized air-conditioned and 'split-unit' type of air-conditioned installed in engineering Campus and Main Campus do not give a significant difference in the perception on thermal environment, respectively.

Acknowledgement

The project is sponsored by Universiti Sains Malaysia under Short Term Grant (grant number 304/JPEB/6311008). The support from the Dean and technical staffs from Schools involved in this assessment is highly appreciated.

References

[1] ANSI/ASHRAE Standard 55-2004. Thermal Environmental Conditions for Human Occupancy. Atlanta, GA. American Society of Heating and Refrigerating and Air-Conditioning Engineers Inc; 2004.

[2] Kosonen, R. and Tan, F. Assessment of productivity loss in air-conditioned buildings using PMV index. Energy and Buildings. 2004;36:987-993.

[3] Pepler, R. D. and Warner, R. E. Temperature and learning: an experimental study, ASHRAE Transactions. 1968:74(1): 211-214.

[4] Fanger, P. O. Thermal comfort. Malabar, FL, USA: Robert E. Krieger Publishing Company;1982.

[5] Awbi, H.B. and Pay, A. A study of the air quality in classrooms. In: Proceedings Second International Conference on Air Quality, Ventilation and Energy Conversation in Buildings, Montreal, Canada, 9-12 May 1995, pp. 93-104.

[6] Bako-Biro, Z., Kochhar, N., Clements-Croome, D., Awbi, H.B. and Williams, M. Ventilation rates in schools and learning performance.

In: Proceedings of Clima 2007 WellBeing Indoors, Helsinki 10-14 June 2007.

[7] Singh, J. Health, comfort and productivity in indoor environment. Indoor Built Environment. 1996:5:22-33.