Thermal Comfort and Occupant Satisfaction of a ...

Computing in Civil Engineering 2015

139

Thermal Comfort and Occupant Satisfaction of a Mosque in a Hot and Humid Climate Gulben Calis1; Berna Alt1; and Merve Kuru1 1

Department of Civil Engineering, Ege University, 35100 Bornova, Izmir, Turkey.

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E-mail: [email protected]; [email protected]; [email protected] Abstract Mosques are distinguished from other types of buildings by having an intermittent operation schedule. They are partially or fully occupied five times a day and the maximum occupancy is expected to occur on Friday prayers. As buildings with intermittent occupancy may not perform the same thermally as typical commercial and residential facilities, thermal comfort conditions and perception of occupants have to be investigated. This paper presents the results of a study monitoring indoor environmental conditions of a mosque in order to assess thermal comfort conditions. A historic mosque, which is located in a hot and humid climatic region of Turkey, was selected as a test building and thermal comfort conditions were monitored during two Friday prayers in August and September. Indoor air temperature, relative humidity and air velocity were collected via data loggers. The predicted mean vote (PMV) and predicted percentage of dissatisfied (PPD) indices were calculated and evaluated using the ASHRAE 55-2010 standard. In addition to this, a questionnaire based on Fanger’s seven-point scale was conducted to understand the thermal sensation and preference of occupants. A comparison is provided to highlight the difference between the calculated and perceived satisfaction of occupants. Keywords: Thermal comfort; PMV; PPD; Mosques

INTRODUCTION Thermal comfort is a key factor that might affect comfort, health, and occupants’ performance (Mendes et al, 2013). It is influenced by a range of environmental and individual factors, both objective and subjective, including air temperature, the temperature of the surrounding surfaces, the air movement, the relative humidity, and the rate of air exchange (Ormandy and Ezratty, 2012). Conventional thermal comfort theories are generally used to make decisions, whereas recent research in the field of thermal comfort clearly shows that important effects are not incorporated (Peeters et.al, 2009). As the conventional theories of thermal comfort are set up based on steady state laboratory experiments, they might not represent the real situation in specific types of buildings such as mosques and churches, which have intermittent operation schedules. A recent study on indoor environmental conditions in mosques indicates that thermal comfort cannot be correlated with ISO 7730 and ASHRAE 552004 standards (Al-Ajmi, 2010). Moreover, occupants can adjust their clothing and activity in response to thermal stress in their environment in typical buildings. However, this adjustment is to a certain extent in mosques due to predefined clothing ensembles and activities.

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Investigation of indoor thermal comfort with respect to thermal performance, problems and possible remedies in mosques has received little attention by researchers. Saeed (1996) conducted a research in the dry desert region in Riyadh, Saudi Arabia, measured thermal comfort in a mosque at Friday prayers during the hot season and evaluated occupant satisfaction by Fanger’s model. The results indicate that occupants attending Friday prayer would prefer a cooler climate than the one recorded in the survey. Al-Homoud et.al. (2009) monitored energy use and thermal comfort in mosques in hot-humid climates of the eastern region of Saudi Arabia. The results show that the relatively high energy use does not guarantee thermal comfort in mosques and enhancing building envelopes with insulation and changing HVAC operation strategies can contribute to thermal comfort. Budaiwi and Abdou (2013) developed a guideline to improve thermal and energy performances of mosques. However, there is still a lack of research on indoor thermal comfort in mosques. The main objective of this study is to investigate thermal comfort conditions and satisfaction of occupants in a naturally ventilated historic mosque in a hot-humid climate. The following sections of the paper describe the experimental design and test site. Then, findings and conclusions are presented. EXPERIMENTAL DESIGN In order to obtain quantitative data on the prevailing actual conditions, the following data collection methods were used: (1) a physical measurement of certain parameters that influence the thermal comfort conditions and (2) a questionnaire as the subjective measurement. Field measurements of the indoor environmental parameters Measurements were taken every minute at a height of 1.1 m from the ground level as advised in the prescriptions of the ASHRAE Standard 55-2010 (ASHRAE, 2010). Indoor air temperature (Ta), relative humidity (RH) and air velocity were measured via the TESTO Thermo-Anemometer Model 435-2. All equipment was calibrated before each experiment to ensure reliability and accuracy in the readings recorded during the field studies. The main characteristics of the measurement system employed in this work are shown in Table 1. Table 1. Main characteristics of the measurement system Parameter Operation range Accuracy Temperature Relative humidity Air velocity

-20 to 50 0C 0-100 % 0-20 m/sn

±0,3 0C ±2 % ±0,03 m/sn scale, +2% reading

Data was collected for an hour with 5 minutes intervals. These parameters were then used to calculate the PMV and PPD indices, in accordance with Fanger’s model. PMV and PPD indices based on Fanger’s model are widely used to understand occupant perception and satisfaction in buildings. Fanger (1970) defined the PMV as the index that predicts, or represents, the mean thermal sensation vote on a standard scale for a large group of persons for any given combination of the thermal environmental variables, activity and clothing levels. The index provides a score that corresponds to the seven point ASHRAE thermal sensation scale, which is presented in Table 2. The PMV should be kept zero with a tolerance

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of ±0.5 scale s units in i order to ensure a coomfortable indoor i envirronment acccording to thhe internatioonal standarrds. The PP PD is an inndex that predicts the percentage of thermallly dissatisfieed people and a is expreessed as a function fu of the t PMV byy Fanger. The T functionnal relationshhip between n the PMV and a PPD inddices are illu ustrated in Figure F 1. As can be seeen from the Figure, 5% of the occuppants are stilll dissatisfied d at the PMV V neutral (0). Table 2. 2 Seven poiint thermal sensation sccale


Scale Sensation n

-3 Cold

-2 Cool

-1 Slightlyy cool

0 Neutrall

+1 Slightlyy warm

+2 Warm m

+3 Hot

Fig gure 1. The relationship p between the t PMV an nd PPD indices he PMV mo odel has beenn validated bby the majorrity of studiees as an accu urate predictor Th of occupaant perceptioon in differeent climatic conditions (Fanger, ( 20002). Fanger’ss PMV moddel is based on theoreetical analyssis of hum man heat exxchange by steady staate laboratorry phreys and Nicol, 20022). The meaan experimeents in Nortthern Europpe and Ameerica (Hump radiant teemperature (T ( r) used in PMV calcullations was estimated ussing the regrression moddel shown in n Equation (1) ( as a fun nction of thee indoor airr temperaturre measured d proposed by b Nagano (2004) ( underr a determinaation factor of 0.99. ×Ta-0.01, R2=0.99 Tr =0.99×

(1)

he operativee temperatuure (To) waas determineed from thee indoor airr temperatuure Th measuredd (Ta) and the mean radiaant temperatture (Tr), as seen s in Equaation (2). Ta +(1-A) ×T Tr To = A×T

(2)

w), as follow ws: where thee weighting factor (A) depends on aiir velocity (w f w