Laskari, M; (2008) Analysis of thermal comfort in a complex atrium under current and future climatic conditions. Doctoral thesis , UCL (University College London).

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Abstract

Because of their multiple functions atria have become very popular among low-energy buildings. In terms of energy efficiency their most significant function is probably their ability to induce stack ventilation and act as a buffer zone for surrounding offices. The purpose of this study was to investigate the thermal performance of a naturally ventilated case study atrium under current and future climatic conditions and their impact on thermal comfort. Thermal comfort conditions under current climatic conditions was estimated through field measurements of Dry Bulb Temperature ( C) and Relative Humidity (%) while possible impacts of global warming were estimated through analysis of dynamic simulation results from TAS with the help of a DSY (Design Summer Year) weather file. In order to understand better the effect of several design characteristics on the thermal performance of the atrium, different simulations were run in TAS initially including and afterwards lacking those design characteristics. The characteristics found significant to be studied in the certain way involved the large internal gains occurring from the basement plant room and the protection border around the cafe area. Conclusions on the effect of the cafe entrance on thermal conditions in the atrium were drawn from a single simulation as it was allowed to do so by its operation schedule. What occurred from this study is that the cafe area of the atrium space does overheat and this tendency will increase significantly in the future. To the overheating, the gains occurring from the plant room have the most critical contribution. However, even though ambient temperatures might seem high, the corresponding dry resultant temperatures that are closely related to thermal comfort, are reduced by the enhanced air flow resulting from the excess heat gains from the basement plant room. Their existence helps maintain internal temperatures higher than external during hot spills thus maintaining the stack for longer. In reducing overheating in the cafe area the protection border also contributes positively. The stack and therefore air flow are strong because of the excess gains of the plant room and the large air intake, but the protection border manages to prevent warm buoyant air from the basement to enter the cafe area. Also, the cafe entrance, when opened, provides an extra air flow into the atrium space that increases the cooling capacity of ventilation. During heating season the buffer zone formed by the atrium space is responsible for maintaining internal temperatures over the often very low external temperatures. In fact, the heat gains from the plant room provide heating to the unconditioned atrium that not only make thermal comfort conditions bearable in the cafe area but also help reduce heating energy demand for the surrounding offices. However, the protection border of the cafe prevents the weak warm buoyant air flow from entering the cafe area and provide heating effectively.

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