الفهرس 
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Abstract
At present, indoor air quality studies are considered crucial for the SARS-CoV-2 pandemic, and approximately half of the energy consumed in the building sector is employed to maintain thermal comfort conditions. However, thermal comfort and indoor air quality are decisive keys that affect the psychological and physiological conditions of occupants as well as their activity level and working efficiency. Therefore, passive solutions with less energy and low carbon emissions are recommended by international organizations to provide comfortable and healthy indoor conditions. In this context, this study deliberates three factors that impact the thermal comfort and the indoor air quality in buildings, with more focus on mosques. To begin with, quantifying the impact of occupancy levels and periods on thermal sensation and CO2 concentrations. In addition, comparing the thermal performance of domed roofs. Furthermore, measuring ventilation rates using the exhaled CO2 tracer gas.
To achieve these objectives, a mosque located in Bahrain named (Al-Hekma mosque) was selected. The readings of air temperature, humidity, air velocity, and CO2 concentration were recorded during real several occupancy levels and periods during the summer season. Then, a numerical comparison was conducted between domed and flat roofs to investigate their impact on thermal comfort using the geometry of Al-Hekma mosque. The recorded data in measurements campaign were inputted to acquire its indoor air conditions and validating the numerical model. Eventually, ventilation rates were estimated using the tracer gas technique for the same mosque. Exhaled CO2 concentrations were traced for different occupancy levels and periods, i.e., 20–200 worshippers during ½ h, 1-h, and 2-h periods. The three known methods of tracer gas technique, namely build-up, steady-state, and decay methods, were examined with respect to measured ventilation rates.
The measured findings of the predicted mean vote (PMV) and predicted percentage dissatisfied (PPD) metrics indicate that the social distancing between worshippers, during the SARS-CoV-2 pandemic, causes a feeling of coolness under the existing cooling system. Meanwhile, the two-hour occupancy period produces a 75% increment of CO2 concentration, 55% during one-hour occupancy, and 20% during half an hour occupancy.
The comparison between domed and flat roofs confirms that under mechanical cooling conditions, the flat roof offers a lower indoor temperature than the domed roof by 0.4 oC and 0.1 oC for open and closed doors, respectively. Similarly, the air velocity is lower by approximately 0.01 m/s for both door modes. The overall PMV values of the flat roof are also lower by 0.07 and 0.01, while the PPD values are lower by 0.20 and 0.34 for open and closed doors, respectively. Based on these small differences, it can be concluded that the thermal performance of both roofing systems behaves similarly in conditioned spaces, however, the air patterns are substantially different.
Tracer gas tests show that a ½ h occupancy period results in a poor correlation between exhaled CO2 concentrations and occupancy levels, which means it misleads estimating ventilation rates in mosques. In contrast, the 1-h and 2-h occupancy periods show a strong correlation. The steady-state, build-up and decay methods show an overestimation of ventilation rates by 10%, 58% and 68% respectively.
Key words:
Thermal comfort; Indoor air quality; Computational fluid dynamics (CFD); CO2 Tracer gas; Predicted mean vote (PMV); Predicted percentage dissatisfied (PPD); Domed roof.