Thermal Comfort in Naturally Ventilated Office Under Varied

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European Journal of Scientific Research ISSN 1450-216X Vol.26 No.2 (2009), pp.260-276 © EuroJournals Publishing, Inc. 2009 http://www.eurojournals.com/ejsr.htm Thermal Comfort in Naturally Ventilated Office Under Varied Opening Arrangements: Objective and Subjective Approach Roonak Daghigh Solar Energy Research Institute, Faculty of Engineering and Built Environment University Kebangsaan Malaysia (UKM) E-mail: rdodper@yahoo.com Tel: +603 - 8921 4596; Fax: +603 - 8921 4593 Kamaruzzaman Sopian Solar Energy Research Institute, Faculty of Engineering and Built Environment University Kebangsaan Malaysia (UKM) Tel: +603 - 8921 4596; Fax: +603 - 8921 4593 Jalil Moshtagh Department of Civil Engineering, University Putra Malaysia (UPM) Tel: +603 - 8921 4596; Fax: +603 - 8921 4593 Abstract This paper investigates the thermal comfort level of an office room through various windows-door opening arrangements. To determine the windows-door opening performance 14 opening configurations have been considered and the combination of opening arrangements was carried out in an office at UPM, Malaysia. After conducting objective measurement for each condition, Predicted Mean Vote (PMV) and predicted Percentage of Dissatisfied (PPD) were calculated. The subjective survey involved questions on the thermal environmental perception and indoor air quality for office occupants. Objective data analysis showed that in none of conditions office had thermal conditions falling within the comfort zone of ASHRAE standard 55, and in all of conditions neutral temperatures are higher than ASHRAE standard requirements. Subjective results revealed that staff has higher thermal comfort level as compared to what PMV has predicted. Keywords: Thermal comfort, Subjective approach, Neutral temperature, Natural ventilation, Objective approach, PMV. 1. Introduction Malaysia is a hot and humid tropical country that lies between 1º and 7º north and 100º and 120º east. Malaysia has a yearly mean temperature of between 26ºC to 27ºC [1] and has high daytime temperatures of 29°C to 34°C [2] and relative humidity of 70% to 90% throughout the year. In recent years, Malaysia’s energy consumption has increased and become comparable to larger energy consumers worldwide. In 2002 the energy consumption was 2.8 MWh per capita and projections show a significant increase in the energy demand. Malaysia has one of the fastest growing building industries worldwide, where the corresponding energy demand would significantly increase in the next coming years [3]. Thermal Comfort in Naturally Ventilated Office Under Varied Opening Arrangements: Objective and Subjective Approach 261 The energy demand scenario in buildings can be understood from the experience of developed nation. Malaysia which is on the track towards a developed nation must understand and proactively be prepared for the potential implication. Considering the average temperature for typical towns in Malaysia, it seems that air conditioning during office hours is a must if people living in the hot and humid climate like Malaysia want a thermal comfort in the building space during the day. Nevertheless, wherever possible if air conditioning can be avoided in the residential houses, without compromising thermal comfort that possibility must be explored [4]. Most of the developing nation like Malaysia intends to develop in a sustainable manner. Sustainable development is defined as the development that meets the needs of the present without compromising the ability of future generations to meet their own needs [5]. The task for those who share the intension of sustainable development is to use energy efficiently, intelligently, and wisely. Through the knowledge of thermal comfort behavior of human and energy utilization behavior of buildings, the best strategy can be adopted. A summary of the neutral temperatures and comfort ranges of subjects in the hot-humid regions is shown in table 1. • The main objectives of this study are as follows: • To identify and evaluate the indoor thermal comfort conditions of naturally ventilated office (via objective measurement) through fourteen different windows-door opening arrangements • To investigate occupants’ perception of the level of thermal comfort in office via subjective approach • To determine neutral temperatures in office for each condition, and • To compare with that prescribed by ASHRAE standard 55–92 [6] and ISO 7730[7]. 2. Research Method Experimental work was conducted in an office room at the 5th level of Mechanical Engineering Department office building (block A) Faculty of Engineering at University Putra Malaysia (UPM). The dimension of room was: 4.10 m by 3.80 m by 2.61 m height (Figure 1 and 2). The volume of room was 41 m3 and its surface area was 15.6 m2. The office consists of three interior walls, interior floor and ceiling, and one exterior wall with window area. The office is normally used by one person but with a possibility to have meetings around a small round table with up to four people taking part. Room was fitted with one window area and one door. The dimension of the window area was: 2.11 by 2.45. Two bottom hung windows which were in window area with the dimensions Width × Height =1.1m×0.47m were mounted 10 cm below the ceiling. For these windows and one door at office room, 14 different opening arrangements were carried out, as shown in table 2. 262 Roonak Daghigh, Kamaruzzaman Sopian and Jalil Moshtagh Figure 1: View of office room and BABUCA Window Table 1: Thermal comfort research for naturally ventilated buildings and air-conditioned buildings in Malaysia and the South East Asia Region. Location Bandung Singapore Singapore-HK Singapore Surabaya Malaysia Bankok, Thailand Singapore1 Singapore2 Singapore3 Bankok Malaysia Penang Jakarta, Indonesia Johor Baru Shah Alam Malaysia Bankok Type of Buildings Type of Study Filed Study Filed Study Filed Study Residential N/a2 Filed Study Thermal Chamber Thermal Chamber MSRB2 Offices Factory N/a Factory Classrooms Classrooms Classrooms Filed Study 1100 32 98 35 70 583 50 50 Filed Study 596 18 -75 54 -76 73 70-80 No. of Subjects 16 5211 118 RH%2 Nutrality Value Tn (°C) =Temp. of Comfort 26 26.2 ET1 26.1 ET (30.0 Ta2) 22-25.5 ET 27.4 26.1 28.5 ET(NV2) 25.4 27.6 27.9 28.5 To2 27.4 ET* 33 28.2 26.7 to (NV+AC) 26 27.4 26.27 27.2 at 0.2 m/s 28.3 at 0.5 m/s 30.3 at 1.0 m/s 31.2 at 1.5 m/s N/a 24.6 28.9 28.8 27.6 26.1 Researcher & Year Published (Mom et al., 1947) [8] (Webb, 1952) [9] (Ellis, 1952) [10] (Ellis, 1953) [11] (Santosa, 1988) [12] (Salleh, 1989) [13] (Busch, 1990)1[14] (de Dear et al., 1991a) [15] (de Dear et al., 1991b) [16] (de Dear et al., 1991c) [17] (Busch, 1992) [18] (Zainal, 1993) [19] (Abdul Shukor & Young, 1993) [20] (Karyono, TH, 1994) [21] (zainal & Keong, 1996) [22] (Abdul Rahman & Kannan, 1997)[23] (Zain Ahmed et.al., 1997) (Khedari et al., 2000) [24] (Sapian et al., 2001) [25] (Ismail and Barber, 2001) (Wong et al., 2002) [26] (Wong & Khoo, 2003) [27] (Sh. Ahmad & Ibrahim, 2003)[28] Azah Ahmad et. al (2004) Sabarinah Sh Ahmad, (2006) Kuala Lumpur Malaysia Singapore Singapore Shah Alam Putrajaya klang valley MSRB A/C office MSRB Classrooms Classrooms Office Residential Filed Study Up to 90 40-80 50-54 1. The old ET scale matces DBT at 100% RH,whereas ET* matches DBT at 50% RH. 2. MSRB:Multi-storey residential building.TO: Operative temperature Ta: Ambient temperature N/a: Not available NV:Naturally ventilated RH:Relative humidity Thermal Comfort in Naturally Ventilated Office Under Varied Opening Arrangements: Objective and Subjective Approach 2.1. Objective Approach 263 The thermal comfort level of the indoor environment is measured using a measuring physical quantities instrument (BABUCA) that was able to measure air velocity, relative humidity, dry bulb temperature and globe bulb temperature. All measurements were taken at a height of 1.0 m above the floor [29], which represents the height of the occupant at seated level. The instrument was placed at work plane level in the rooms at 1.5 meters from the window. These measurements were carried out at one point at the middle of office. The samples were recorded every one minute interval. In this study, the metabolic rate is set to be 1.2 met [30] which is sedentary activities (office, dwelling, school, laboratory) whereas the Clo-value (thermal resistance) is set to be 0.5 where the males were wearing underpants, shirt with short sleeves, light trousers, light socks and shoes. The females were wearing ‘baju kurong’ which is cotton or silk with light cotton undergarments and a lightweight scarf. BABUCA located inside the office and one sampling location inside the room (the middle of the room) was considered. The sampling location inside the room was at a height of 1.0 m above the floor. The experiment protocol was as follows: at the beginning windows and door were closed, whenever BABUCA started measuring physical quantities, one of 14 different opening arrangements was carried out. The precision of the test method was determined by thermal comfort parameters measurements, 15 times for each condition, the mean coefficient of variation of the 15 duplicated tests for PMV-PPD was 1%. Figure 2: View of office room and BABUCA 264 Table 2: Roonak Daghigh, Kamaruzzaman Sopian and Jalil Moshtagh Variable Conditions of Windows-Door Arrangements for Naturally Ventilated Office Room Windows Positions Two Windows Closed Two Windows Opened Windows No.1 and No.2 Half Opened Window No.1 Fully Opened, Window No.2 Closed Window No.1 Half Opened, Window No.2 Closed Window No.2 Fully Opened, Window No.1 Closed Window No.2 Half Opened, Window No.1 Closed Two Windows Closed Two Windows Opened Windows No.1 and No.2 Half Opened Window No.1 Fully Opened, Windows No.2 Closed Window No.1 Half Opened, Window No.2 Closed Window No.2 Fully Opened, Window No.1 Closed Window No.2 Half Opened, Window No.1 Closed Code Naturally Ventilated Conditions A (Control) U W1 E F1 G H C1 Z V1 M1 N O P Door Position Closed Opened 2.2. Subjective Measurements Subjective thermal comfort data were recorded using a questionnaire; the questionnaire developed for this survey was divided into four main sections: a) Demographic Information, b) Current status of thermal comfort, c) Use of controls, d) Thermal sensation and preferences, and e) Current clothing garment. A sample size of 60 subjects, all staffs, took part in the survey. The staffs were given one hour to answer the questionnaire and to return it. The dominant gender distribution sampled was male (66.6%) The total response rate was 100%. Prior to the survey, the subjects would have been seated at their chairs for approximately 30 min [31], with mostly sedentary activities. Sufficient time for body precondition in each survey was necessary to maintain respondent’s metabolic rate (M) at the same level throughout the study which was estimated to be equal to 1.2 met. 3. Results and Discussions 3.1. Evaluation of Thermal Comfort The thermal comfort parameters and outside air measurements are presented in table 3 and Figures 5 to 18 show Predicted Percentage of Dissatisfied (PPD) as a Function of Predicted Mean Vote for Naturally Ventilated Office. Thermal Comfort in Naturally Ventilated Office Under Varied Opening Arrangements: Objective and Subjective Approach Table 3: 265 Measurements of Thermal Comfort, Outside Air Parameters, Neutral Temperatures (Mean Values) Outside Air Parameters (Mean Values) Relative Humidity (%) Air Temperature (ºC) Neutral Tem. (ºC) Air Velocity (m/s) Neutral Temperature (ºC) 80% Accept. 90% Accept. Thermal Comfort Parameters (Mean Values) Relative Humidity (%) Mean Radiant Temp. (ºC) Dry Bulb Temp. (ºC) Air Velocity (m/s) Tn + 2.5 A U W1 E F1 G H C1 Z V1 M1 N O P 30.4 26 31.4 30.6 30.4 30.1 32.9 30.2 25.9 29.2 26.0 30.4 29.8 30.5 57.7 61 57.6 66.2 57.4 60 54.1 58.9 60.4 56.3 63.2 65.3 67.3 65.4 0.03 0.21 0.05 0.06 0.08 0.08 0.1 0.03 0.34 0.11 0.09 0.05 0.12 0.08 34.8 29.8 32.7 32.5 33.2 31.5 34.7 33 27.6 31 30 32.1 30 32.1 31.7 25.6 31.7 31 31.3 30.8 32 31.6 24.6 30 26 30.8 29.1 30.7 73.6 62 62.2 71 60.1 65.4 60 63.5 61 72.3 65 71.8 71.2 74.1 0.3 0.65 0.61 0.31 0.12 0.29 0.20 0.28 0.79 0.43 0.35 0.49 0.51 0.40 27 25.7 27.3 27.1 27 26.9 27.8 27 25.6 26.7 25.7 27 26.8 27.1 24.5 23.2 24.8 24.6 24.5 24.4 25.3 24.5 23.1 24.2 23.2 24.5 24.3 24.6 29.5 28.2 29.8 29.6 29.5 29.4 30.3 29.5 28.1 29.2 28.2 29.5 29.3 29.6 23.5 22.2 23.8 23.6 23.5 23.4 24.3 23.5 22.1 23.2 22.2 23.5 23.3 23.6 30.5 29.2 30.8 30.6 30.5 30.4 31.3 30.5 29.1 30.2 29.2 30.5 30.3 30.6 3.1.1. Data Analysis Based on Simulation with Reference to the ISO 7730 and ASHRAE 55-92 [32] This analysis resulted from the measurement in the middle of December, 2006 from 9.00 a.m. to 17.00 p.m. (working hours). From the analysis using InfoGap and Microsoft Excel, the Microclimate Indexes Calculation in Moderate Environment shows that the ranges of predicted mean vote (PMV) for naturally ventilated office for 14 conditions was between -0.8-2.8 as shown in Table 2. The comfort range was taken to be the conditions when the PMV has the values between –1 and +1, Results showed that the office is not within the comfort range during working hours for most of all conditions in naturally ventilated office, except for these conditions: Z, U and M1. Figure 3 shows the variations of thermal comfort parameters and air exchange rate during this period of time as a sample graph for control condition (A). The ASHRAE Standard 55-1992 states that the comfort zone for summer conditions in cold countries air temperature to be between 23ºC to 26ºC and relative humidity between 20% to 60 %. Results showed that the office is not within the comfort range during working hours for all conditions in naturally ventilated office. Tn + 2.5 Code Tn - 2.5 Tn - 2.5 266 Roonak Daghigh, Kamaruzzaman Sopian and Jalil Moshtagh Figure 3: Variation of Thermal Comfort Parameters and Air Exchange Rate vs. PMV for Control Condition 3.1.2. Discussion Based on ASHRAE 55 – 1992 using Psychometric Chart Figure 4 shows that the office is not within the comfort range during working hours for all of conditions in naturally ventilated office. Figure 4: Thermal Comfort Range Based on Psychometric Chart – ASHRAE 55 for All Conditions – All Conditions 3.1.3. Discussion With Respect to Neutral Temperature Numerous climate chamber and filed studies have been conducted in hot humid South East Asian and the surrounding regions since the 1930s. In all studies, the proposed neutral temperatures are higher than 24.5ºC recommended by ASHRAE Standards 55. For the indoor design conditions, the comfort Thermal Comfort in Naturally Ventilated Office Under Varied Opening Arrangements: Objective and Subjective Approach 267 range for all studies have higher maximum values, some at 4ºC higher than the recommended range (23ºC to 26ºC) for air-conditioned buildings. For naturally ventilated buildings, the neutrality temperatures 26.1ºC and 27.4ºC for Malaysia ([23] and [1]), found earlier correspond well to 27.4ºC ET* obtained in Thailand and 28.5ºC in Singapore [17]. In this study the neutrality temperatures for 14 conditions are between 25.2ºC -27.5ºC. Based on [32]' equation, for 90% acceptability for thermal comfort suggested is Tn ± 2.5 K and 80% acceptable for comfort suggested Tn ± 3.5 K. 80% and 90% acceptability for each condition are given in Table 3. Figure 5: Condition A- PPD as a Function of PMV. (ISO 7730) P P D (% ) -3 -2 -1 100 90 80 70 60 50 40 30 20 10 0 0 PMV 1 2 3 Figure 6: Condition U- PPD as a Function of PMV. (ISO 7730) 100 90 80 70 60 50 40 30 20 10 0 -3 -2 P P D(% ) -1 0 PMV 1 2 3 Figure 7: Condition F1- PPD as a Function of PMV. (ISO 7730) 100 90 80 70 60 50 40 30 20 10 0 -3 -2 P P D (% ) -1 0 PMV 1 2 3 268 Roonak Daghigh, Kamaruzzaman Sopian and Jalil Moshtagh Figure 8: Condition W1- PPD as a Function of PMV. (ISO 7730) 110 100 90 80 70 60 50 40 30 20 10 0 0 PMV 1 2 3 -3 -2 Figure 9: Condition G- PPD as a Function of PMV. (ISO 7730) PPD (% ) -1 100 90 80 70 60 50 40 30 20 10 0 -3 -2 P P D (% ) -1 0 PMV 1 2 3 Figure 10: Condition H- PPD as a Function of PMV. (ISO 7730) 100 90 80 70 60 50 40 30 20 10 0 -3 -2 P P D (% ) -1 0 PMV 1 2 3 Figure 11: Condition C1- PPD as a Function of PMV. (ISO 7730) 100 90 80 70 60 50 40 30 20 10 0 -3 -2 P P D (% ) -1 0 PMV 1 2 3 Thermal Comfort in Naturally Ventilated Office Under Varied Opening Arrangements: Objective and Subjective Approach Figure 12: Condition Z- PPD as a Function of PMV. (ISO 7730) 269 100 90 80 70 60 50 40 30 20 10 0 -3 -2 P P D(% ) -1 0 PMV 1 2 3 Figure 13: Condition V1- PPD as a Function of PMV. (ISO 7730) 100 90 80 70 60 50 40 30 20 10 0 -3 -2 PPD(%) -1 0 PMV 1 2 3 Figure 14: Condition M1- PPD as a Function of PMV. (ISO 7730) 100 90 80 70 60 50 40 30 20 10 0 -3 -2 PPD(%) -1 0 PMV 1 2 3 270 Roonak Daghigh, Kamaruzzaman Sopian and Jalil Moshtagh Figure 15: Condition O- PPD as a Function of PMV. (ISO 7730) 100 90 80 70 60 50 40 30 20 10 0 -3 -2 P P D(% ) -1 0 PMV 1 2 3 Figure 16: Condition N- PPD as a Function of PMV. (ISO 7730) 100 90 80 70 60 50 40 30 20 10 0 -3 -2 PPD(%) -1 0 PMV 1 2 3 Figure 17: Condition P- PPD as a Function of PMV. (ISO 7730) 100 90 80 70 60 50 40 30 20 10 0 -3 -2 P P D (% ) -1 0 PMV 1 2 3 Thermal Comfort in Naturally Ventilated Office Under Varied Opening Arrangements: Objective and Subjective Approach Figure 18: Condition E- PPD as a Function of PMV. (ISO 7730) 271 100 90 80 70 60 50 40 30 20 10 0 -3 -2 P P D(% ) -1 0 PMV 1 2 3 3.2. Subjective Assessment Assessment of thermal comfort in the office was based on responses to a questionnaire survey, which was administered simultaneously with the physical measurements in each condition. A total of 60 respondents participated in the survey for each condition, out of which 40 were female and 20 were male. They were from different offices. The basic demographic data of the respondents are summarized in table.4. Table 4: Demographic data of respondents Age (Years) Male Female Total Below 20 20-30 3 27 30 30-40 9 15 24 Above 40 6 6 Total 12 48 60 3.2.1. Type of Clothing Worn Figure 19 shows the type of clothing of staff in the office during working hours. 90% of female and 100% of male were wearing baju kurong and long pants and short sleeve shirt. In respect to afore mention, equivalent Clo-value is set to be 0.5. Figure 19: Type of Clothing Worn 100 80 (% ) 60 40 20 0 Baju Kurung Long Pants & Long Sleeve Shirt Long Pants & Short Sleeve Shirt 272 Roonak Daghigh, Kamaruzzaman Sopian and Jalil Moshtagh 3.2.2. Analysis of Votes on ASHRAE Scale Figure 20 shows the profile of Thermal Vote cast on the ASHRAE scale for office room at all conditions. From the relative frequency of votes in each category, it can be seen that in the most conditions the thermal vote centered around 1 (slightly warm). Figure 20: Relative Frequency of ASHRAE Thermal Votes Analysis of Votes on ASHRAE Scale 100 90 80 70 60 50 40 30 20 10 0 -3 -2 -1 0 1 2 3 P e rc e n ta g e o f V o te s (% ) ASHRAE Thermal Sensation Scale A U W1 E F1 G H C1 Z V1 M1 N O P 3.2.3. Adaptive Behaviour Figure 21 explains the list of adaptive actions commonly occurred in office for condition A as a sample graph and their percentage of people who choose to employ them for this condition. For control condition the environmental control by turning on the air-conditioner and opening the windows (in absence of air conditioner) is highly preferred by staff with 100 to 93.3%, respectively. Other favoured adaptive actions are opening the door and going out to cooler places with 66.6% and 53.3%, respectively. Getting a drink constitute 46.7%. The least favourable action was changing clothes which showed only 13.34%. The usage of fan in office showed the percentage of 0% as office had no fan. Figure 21: Adaptive Behavior for condition A Curtains Door Adaptive Actions Clothing Drink Window Air Cond. Go Out Fan 0% 10% Always 20% 30% 40% 50% Often 60% 70% 80% 90% 100% Most Likely Seldom Very Unlikely 3.2.4. Assessment of Air Quality The main types of complaint from the staff for control condition are stagnant air; humid and dusty, details are shown in Figure 22 reflects the opinions of the staff on the air quality in the office room for control condition. Thermal Comfort in Naturally Ventilated Office Under Varied Opening Arrangements: Objective and Subjective Approach Figure 22: Complaints from staff on physical parameters (Control condition) 273 Breezy Types of Complaint (Physical Parameters) Hot Dry Humid Still Draughty Smelly Dusty 0 10 20 30 40 50 60 70 80 90 No. of Complaint, (% ) In control condition 80% of staff claimed that the air was still. It is most likely believed that still air inside office was due to the low mean air velocity (0.03 m/s) and the outside (fresh) air provision to the premises was insufficient as determined from the ventilation analysis. It is in connection to what have already been found in this study. As a sample graph, Figure 23 shows the opinions of staff on the air quality in the office for 14 conditions. Figure 23: Distribution of Air Quality for Naturally Ventilated Office A U W1 E F1 G H C1 Z V1 M1 N O P 100 (%) of respondents 80 60 40 20 0 Acceptable Air Quality Unacceptable In most conditions staffs were almost satisfied with the air quality, therefore, air quality in the office room was within tolerable limits for staff, although in most conditions only relative humidity fulfills ASHRAE-62 requirements. 4. Discussions Results obtained from complaints from staff on physical parameter in some conditions especially when the windows and door are closed consistent with the fact that most of staff expressed that the air was 274 Roonak Daghigh, Kamaruzzaman Sopian and Jalil Moshtagh still showed that the office had an unacceptable air exchange rate. This is due to the low mean air velocity in these cases, and the outside (fresh) air provision to the premise is insufficient. Inadequate ventilation will give rise to a poor indoor air quality. In most conditions staffs were satisfied with the air quality, so the subjective assessment showed that air quality in the office room was within tolerable limits for staff, in spite of in most conditions could not fulfill ASHRAE-62.1-2004 requirements. The calculated PMV and PPD indices by BABUCA indicating that the occupants perceived the room is warm in most of conditions, but adaptive behavior allows the occupants to control their own local thermal environment by adjusting and doing adaptive action. Results obtained from the survey showed that in the most conditions the thermal vote centered around 1 (slightly warm) and by equating the central three categories of the ASHRAE scale with the notion of acceptability, some of the occupants are assumed to be satisfied with the thermal condition in their office. There are people who vote beyond the center three category and yet find their environment acceptable. Results of these study suggest a wider thermal comfort range for Malaysian than that proposed by international standards, i.e., ASHRAE Standard 55, which indicates that Malaysian are acclimatized to much higher environmental temperatures. The result of this study is also in accordance to other studies in Malaysia and surrounding regions ([17]; [14]; [23 and [1]). Therefore adopting the international standards for interior comfort conditions for the Malaysian hot and humid tropical climate may lead to overcooling and energy waste. The result of this study is also in line with the current revisions to ASHRAE standard 55 that will include a new adaptive comfort standard (ACS) that allows warmer indoor temperatures for naturally ventilated buildings in warmer climate zones. It can be observed that the state of temperature for naturally ventilated office in most of conditions are far from the thermal comfort of 26°C from the guideline given by Malaysian Energy Efficient Guideline[34], thus hard to achieve thermal comfort during office hours from natural ventilation according to [33]. The Department of Standards Malaysia [34] recommended indoor design temperature range from 23ºC to 26ºC. Indoor thermal comfort can be improved significantly by controlling window-door opening appropriately in accordance with the temporal variations of indoor and outdoor climates. Results of this study showed that, when outside air velocity is more than inside,hence with opening windows and door, inside air velocity will be increased, then thermal comfort is increased. If the staff is dissatisfied with the uncomfortable condition they prefer take some corrective actions, which can be classified in general as personal and environmental adjustments. Personal adjustments such as: getting more drink, changing cloths and environmental adjustments are active controls such as opening windows, door, etc. From this research, it is revealed that when windows-door opening arrangements applied if the outdoor temperature is lower than indoor temperature thermal comfort indices and staff satisfaction enhance. Staff prefer to control environment via opening windows-door rather than personal adjustment such as adjust their clothing. 5. Conclusions • • • The comfort range was taken to be the conditions when the PMV has the values between –1 and +1, based on ISO 7730-94. Thermal Comfort study of the office showed that in most of conditions, PMV and PPD indices for office had no falling within these ranges. Thermal Comfort study of the office showed that in all of conditions, the office had no thermal conditions falling within the comfort zone of ASHRAE standard 55-92, as expected, in most conditions, naturally ventilated office was warm. In this study the neutrality temperatures for 14 conditions are between 25.2ºC -27.5ºC.Occupants of naturally ventilated office expressed satisfaction with indoor climate conditions well outside of the boundaries set by the ASHRAE standard’s comfort zone. Occupants found temperature range beyond the comfort zone acceptable. This study shows that the acceptable temperatures, implying that the ASHRAE standard 55–92 is not applicable in the naturally ventilated office in hot and humid climate. Results of this study suggest a wider thermal comfort range for Malaysian than Thermal Comfort in Naturally Ventilated Office Under Varied Opening Arrangements: Objective and Subjective Approach 275 • that proposed by international standards, which indicated that Malaysian are acclimatized to much higher environmental temperatures. The information obtained from questionnaires show that the air quality has some problem in naturally ventilated office. They claimed that the air was still. This problem was solved in conditions which air movement was improved by opening windows or door. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] Sabarinah, S.H., Ahmad (2006). 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