Decision-Making Support in Early Design Stage for High Performance Naturally Ventilated Buildings
AbstractWhile a lack of design decision-making support for natural ventilation evaluation in the early stage is noticeable, the interest in high performance naturally ventilated buildings has been rapidly growing in recent years. As a response, the target of this dissertation was to develop a design decision-making support system, including a new index and a calculation procedure, to help designers make better informed decisions in the early stage by taking natural ventilation into account.
To achieve this goal, the objective of this research had to be defined first. This meant defining the index to be used when evaluating natural ventilation in the early design stage. The study began by reviewing current practices of natural ventilation evaluation in the literature and identifying the problems of current indices. Considering the precision criterion was special for this stage and the available design information was limited, a new index had to be developed. A Design-Based Natural Ventilation Potential was proposed as the evaluation index of natural ventilation, especially for the early design stage.
After defining the objective, a procedure for calculating the natural ventilation evaluation index was developed. The calculation procedure study consisted of two main parts, outdoor wind environment simulation and indoor natural ventilation calculation. For the outdoor wind environment simulation, an automatic process of computational fluid dynamic (CFD) simulation was suggested to provide a wind pressure coefficient database on the facade, including the influence of weather conditions and the urban context. Results would be used as boundary conditions for the indoor natural ventilation calculation. For the indoor calculation, a simplified calculation method was proposed as the solution to complete a quick natural ventilation evaluation during the early design stage. To achieve the simplified calculation method, similarity analysis was conducted, and then CFD simulation was employed to perform numerical experiments. Simplified calculation equations were built by regression of the numerical experiment results and were validated. The equations provided similar results to CFD simulation, but with much less time. Cross-ventilation was used to illustrate development of the simplified calculation method. In the end, a practical way to evaluate the Design-Based Natural Ventilation Potential was found using the automatic outdoor wind environment simulation and the simplified indoor natural ventilation calculation.
Lastly, a case study was employed to illustrate the possibility of this decision-making support system for natural ventilation evaluation in the early design stage. The design decision-making support system was embedded in the architectural modeling software to provide quick feedback on the design. Scripts were developed to carry out the natural ventilation evaluation calculations in Grasshopper. A building form optimization study was conducted based on the potential for natural ventilation evaluation in the early design stage, showing the advantages of this support system for designers.
In conclusion, a comprehensive and practical natural ventilation evaluation to help with decision-making in the early phase of design was developed in this research. This innovation enables better informed design decisions early in the design process.
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