Effects of opening to wall ratio (OWR) on indoor thermal comfort of praying hall in urban Mosque, Kuala Lumpur

Abstract

Opening design and Opening to Wall Ratio (OWR) have significant effects on the thermal comfort level of a building. The design of façade openings in the mosque usually focuses on aesthetic consideration as opposed to work as a mechanism to control indoor thermal comfort. Nowadays, the majority of the mosques improve the indoor thermal comfort by installing air-conditioning systems. The mosques are primarily used daily at prayer times including Friday prayer. The usage of air-conditioning increases the energy consumption and electricity cost since the mosque deals with intermittent occupancy. Most of that time, the mosque is unoccupied. Therefore, the usage of air-conditioning systems for thermal comfort incur the unnecessary increase in energy usage and cost. Literature review in this research focuses on urban mosque, façade design and thermal comfort. The definition of urban mosque and façade openings identified in this research is significant to identify the typology and criteria of OWR of urban mosque. Moreover, the research uses a quantitative approach by means of Urban Mosque Façade Design (UMFD) based on OWR Inventory and computer simulation on thermal analysis of air temperature. The UMFD-OWR inventory is significant to determine the configurations of OWR of UMFD for thermal analysis, while computer simulation is used to investigate the effects of OWR on indoor thermal comfort in praying hall. The term opening adopted in this research are operable doors, fixed and operable windows and opening such as arch, void and etc. The OWR also focuses on middle section of the façade form of both North-West Façade (NWF) and South-West Façade (SEF). The final samples selected for thermal analysis are OWR M1, OWR M2, OWR M3 and OWR M4 on UM model for thermal simulation. The highest opening ratio is OWR M2 and the lowest is Base Case Model (OWR BM) which acts as a reference and comparison between the other models. All the models are simulated in ECOTECT and analysed based on Hourly Temperature (HT), Annual Temperature Distribution (ATD) and Passive Adaptivity Index (PAI). The research found that the indoor temperature for HT recorded in ECOTECT is within the comfort range for naturally ventilated building (23.6?C -30.7?C) during Subuh and Isya’ on the hottest day, and Subuh, Maghrib and Isya on the coolest day. OWR BM (lowest opening ratio on UMFD) recorded highest comfort percentage (ATD) and better PAI compared with others models. All the findings on thermal analysis in ECOTECT showed that the variations of opening ratio influenced the heat gain through radiation and internal load (number of occupancies) and heat loss through the outdoor air movement (cross ventilation and stack effect). The comparison on OWR M2 between ECOTECT and IES-VE, IES-VE predicted lower indoor temperature reading in the praying hall. The accuracy of the results can be further investigated through field measurement in further research. Thus, further research is also encouraged to explore more on façade design strategies without specific on certain design (i.e. opening) in reducing the indoor temperatures in an urban mosque in order to fulfil the indoor design conditions.