| Summary: | Maintaining IAQ (Internal Air Quality) and thermal comfort of occupants in buildings have been a challenge to overcome satisfying the two ends: criteria for sustainability and cost effectiveness. Although there was a movement for mechanical ventilation systems in the recent past, in addition to the cost involved, they are found to not deliver the desired air quality, lead to social consequences such as sick building syndrome, contribute to environmental consequences related to ozone-depleting substances with increasing energy consumption, generate noise and having difficulties in cleaning and maintaining. These consequences compelled research on natural ventilation systems, which were used in ancient buildings. Although it has been found that natural ventilation of buildings can become a substantial architectural design tool that leads to “breathing architecture,” fluctuations in indoor temperature and air quality makes depending entirely on natural ventilation less effective. The combination of natural and mechanical ventilation, the hybrid ventilation or mixed-mode ventilation, systems utilizes advantages and eliminates drawbacks from both mechanical and entirely dependent natural ventilation systems. Hybrid ventilation systems, which have been utilized in historical buildings, with less investment cost and reduction of energy usage have been found to be a solution to provide acceptable standards of IAQ and thermal comfort through natural air circulation in buildings. This research study was carried out to verify the effectiveness of a hybrid ventilation system in an auditorium built around 60 years back for its effectiveness as a provider of thermal comfort to its occupants. Computational Fluid Dynamic (CFD) modeling was carried out on a Finite Element (FE) model owing to its capability of offering a wide range of flexible analytical solutions, lower realization time and comparative cost effectiveness to experimental methods of modeling. This verification of the system has revealed that hybrid ventilation systems could provide effective thermal comfort in buildings designed specifically to allow circulation of air through the system. The results of the study were in agreement with measured data and the expected flow of air through the building when the thermal load due to metabolism of occupants was not included in the analysis. In addition, the expected results complied with similar studies on natural/hybrid ventilation systems. With the addition of the thermal load, as a uniform heat flux from the flow of the auditorium, it was observed that the conditioning of the air throughout the space was better than the without thermal load scenario. In the case modeling people as cylinders, with a convective heat flux, it was observed that the air flow direction changes and the seating level of the auditorium do not get sufficient air flow to maintain a comfortable air quality. Ineffective simulation of the inlet louver was assumed to be the primary reason for this scenario and other reasons such as the seating arrangement modeling too could have effects on the result. As conclusions of the study it was found that the whole building system properties have to be selected, as the control component to produce operating commands, to circulate air through the building in accordance with the air flow: both velocity and patterns, required to maintain thermal comfort of all occupants. Air inflow could be through windows as acquisition components to collect indoor and outdoor climatic parameters and air outflow could be mechanically controlled through exhausted fans turning on or off as the operating component in the system. The result of the study ensures the method of solutions through CFD to be utilized to provide effective and less costly path to verify systems such as natural or hybrid air flow systems through buildings. The whole system studied could be applied with suitable contextual modifications to any new location, with similar cost effective modeling, to produce less fuel consuming building systems leading to sustainability of built environment.
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