Numerical assessment of night ventilation impact on the thermal comfort of vernacular buildings

Abstract

Night ventilation, is one of the most effective passive cooling techniques that may contribute to the improvement of the occupants thermal comfort conditions. Despite the justified effectiveness of night ventilation, few studies quantified its influence on the thermal comfort of vernacular buildings, especially under warm dominant climates. The aim of this study is the investigation of the impact of night ventilation on the thermal comfort of vernacular buildings under summer dominant environmental conditions. The subjects under investigation was one traditional buildings in the city of Nicosia in Cyprus. In terms of this study numerical analysis regarding the thermal comfort of the investigated buildings was performed by employing Energy Plus and the flow solver of Design Builder. The indoor operative temperature distribution, the indoor air velocity and a thermal comfort related index were identified in selected thermal zones of the examined building using night ventilation. The results of this study quantified the potential temperature decrease that can result on vernacular buildings due to the use of night ventilation and revealed some restrictions with regard to the allowed percentage of the opening sizes towards achieving optimal thermal conditions in space. This study aspires to provide useful insight regarding the importance of humans' behavior in terms of enabling night ventilation to vernacular buildings, as well as to con-tribute to the ongoing scientific discussion on this subject.

A literature review of night ventilation strategies in buildings

“…Their findings showed the possibility of eliminating air-conditioning during the full working period, and depending on which category of comfort is set, the temperature reduction averages 1 °C. The impact of NV on improving internal thermal comfort levels was studied by Exizidou et al [17]. The outcomes of the study demonstrate that the average PMV index for the non-ventilated and night ventilated zones was 2.25 and 1.1 respectively.…”

“…Al-Ain city, United Arab Emirates (BWh) Low-Rise heavy residential buildings Improving NV with a combined wallroof solar chimney [31,32] A full-scale model (EnergyPlus) derived form an experimental model in Arizona [33] Yazd, Iran (BWh) A typical office building with lightweight structure Combined use of PCMs to optimise NV [17] Simulations of EnergyPlus and the flow solver of Design Builder Nicosia, Cyprus (BSh) Vernacular buildings…”

“…Night ventilation (NV) is an effective passive cooling technique whereby the daytime heat gain of a building is released at night-time through the intake of the outdoor cool air. That is, the colder nocturnal air that circulates through the building during night ventilation cools the indoor air and building fabric; afterwards, the consequent cooled structure slows the rate at which the internal temperature rises during the day [12][13][14], thereby decreasing the cooling energy demand [15,16] and improving occupant thermal comfort [17]. Passive cooling is the interaction of all measures acting to decrease heat gains coupled with accessible heat storage and heat sinks [18].…”

The Effect of Climate Change on Weathering: Evidences from Heritage Buildings under Subtropical Conditions

“…Also, through climate modeling over the last decade, it's been demonstrated that the temperature has risen by 1 to 3 C⁰ and it's estimated that by the end of the century, the yearly period of high temperatures (excess of 38 C⁰), i.e. the summer season, will last an additional 2 months, resembling the conditions in cities like Cairo and Bahrain (Exizidou et al, 2017). These temperature fluctuations of cooler nights (25 C⁰) and warmer days showcase a magnitude of difference of around 15 C⁰, that can lead to an excessive rate of deterioration of facades due to the higher thermal stresses developed in the materials (Christoudias et al, 2012).…”

Indoor Air Temperature Distribution and Heat Transfer Coefficient for Evaluating Cold Storage of Phase-Change Materials during Night Ventilation

“…The indoor temperature reduction effect by night ventilation is significantly affected by the heat capacity of the building, the amount of ventilation, and the change in outdoor temperature [6]. Exizidou et al [7] found that thermal comfort levels improved by an average of 26% with the use of night ventilation in vernacular buildings. Geros et al [8] presented the key parameters, which include the effective night-time airflow rate, as well as the indoor-outdoor temperature differential.…”