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BCIT Thesis and other Required Graduate Degree Works
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- Assessment of natural ventilation design and efficacy in a net-zero energy house
- Achieving acceptable indoor environmental quality and thermal comfort in buildings can be difficult without relying on energy intensive mechanical equipment. When the climate conditions permit, natural ventilation could potentially help minimize the reliance on mechanically conditioned air; however, natural ventilation is rarely engineered. Houses are typically designed as fully enclosed climate systems in which the connection with the outdoor environment is rarely planned. Unlike in commercial or specialized buildings, houses are not designed with many energy conservation measures in mind. Reconnecting them with the outdoors has a great potential to increase thermal comfort and reduce reliance on mechanical systems. With such a connection to the dynamic weather conditions of the outdoors, it is difficult for architects to choose beneficial design elements to be included in the construction of their houses. Knowing which elements work and to what extent under particular conditions can potentially achieve increased thermal comfort using little or no energy. This research aims to offer a thorough assessment of a case study house and determine the effects of the design choices made by the architect of the house. This research may help architects know the risk factors affecting natural ventilation design in a systematic manner; and in doing so, enable quantifying the benefits of natural ventilation to meet the design goals of maintaining satisfactory indoor conditions without the use of air conditioning, particularly in the summer. A constructed net-zero case study house located in the Pacific marine climate of Canada was used to develop the proposed research. The house had been designed by an architect to rely solely on natural ventilation for cooling during the summer and much of the spring and fall. The house was instrumented and its indoor environment was monitored for a period of several months in 2014 to collect data to evaluate the effectiveness of design choices made, including the effect of a large atrium and the air flow characteristics of the windows intended by the architect to deliver most of the ventilation. Recorded data showed the house performed commendably and this was confirmed through evidence from the home owners. To aid in the understanding of the dynamics of the Harmony House, whole-building, multizone air flow network modeling and computational fluid dynamics (CFD) modeling of the house was developed and calibrated with monitored data and testing. The models were used to assess the indoor air quality and further quantify the natural ventilation of the house, as well as test hypothetical situations that were once considered for the house. Simulations revealed some additional insight into the design choices that were implemented in the house and showed that further technologies intended to increase ventilation were unnecessary and some instead, reduced ventilation through the house.
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- Assessment of natural ventilation using whole building simulation methodological framework
- Natural ventilation is a passive alternative to provide both indoor air quality and thermal comfort for the building’s occupants with low energy use. But at the same time, it is challenging for the building designers to implement natural ventilation strategies due to its complexity and highly dynamic behaviour, especially when it is compared with the mechanically ventilated buildings. Nevertheless, the use of naturally ventilated buildings is increasing along with the use of passive strategies, but depending on the complexity of the project, the designer still use rules of thumb for the implementation of natural ventilation strategies instead of a more comprehensive simulation-based approach. In theory, whole building simulation models (WBSM) are becoming viable tools to support natural ventilation design, particularly in the early stages of the project where the impacts of measures to implement a natural ventilation strategy are magnified. However, the only “evidence” of such level of support comes from individual case-study projects. Nevertheless, there is a lack of validation through measurement of the effectiveness of natural ventilation design in real buildings. This research will shed light into the “inner-workings” of natural ventilation models in WBSM to answer fundamental questions such as the following: How is wind data processed? How are envelope openings characterized? How are internal openings modelled? When and how is air buoyancy modelled in spaces? How are the coupled thermal and fluid mass transfers modelled to reflect the dynamic thermal responses of constructions and airflows? Therefore, a methodological framework is developed in order to provide the necessary knowledge for natural ventilation assessment. This framework is based on simulation (WBSM) and field testing. The proposed framework is tested in an existing landmark building in Vancouver. A WBSM of that building is developed, calibrated, and used to analyze how different factors that compose an integrated natural ventilation strategy (like the building shape, window shading, thermal mass, indoor spaces functionality and connectivity, and local climate) influence the thermal comfort of its occupants., Natural ventilation, Thermal comfort, Adaptive model, Whole building simulation models (WBSM)