Variability of wind effects on natural ventilation and pollutant transport in buildings

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1605091 Lo, Liang Chung J.With expanding energy consciousness in the building sector, architects and engineers have been increasingly using natural ventilation as a means to reduce energy expenditures. While natural ventilation has been used for thousands of years in various culture worldwide, the current modern method of designing for natural ventilation is simplistic and assumes steady flow, thus misestimating actual natural ventilation rates and their associated energy and indoor air quality impacts. The key reason behind such difficulty is the inherent unsteadiness of the wind in both its direction and magnitude. Unlike mechanical ventilation, which is driven by fans with well-tuned control, the wind's effect on ventilation is wholly unpredictable given the current approach. Such lack of knowledge may result in unintended consequences in energy consumption, human comfort, and even the overall health and wellbeing of the occupants. To better understand the consequences on building airflow and occupants of wind variability, this research project will analyze quantitatively, for different building forms and locales, the impacts of wind-driven natural ventilation flow in terms of ventilation effectiveness, energy consequences, and indoor air quality.These goals of the research project will be accomplished by: 1) Researching the ideal formulation of a probabilistic transient wind effect framework that describes wind's variable impacts on buildings, as well as researching what minimum time scale that metric should operate on; 2) Simulating wind-building interactions in the nine National Oceanic and Atmospheric Administration (NOAA) established climate zones in the contiguous United States for a selections of building types from Department of Energy's representative building stock in the U.S., using both computational fluid dynamics (CFD) methods and quasi-steady state approximations; 3) Investigating a broad spectrum of factors of the impact of the framework, such as ventilation effectiveness, energy impacts, and indoor air quality and occupant productivity and health. The research is anticipated to impact the building design process by allowing engineers to properly design for the wind harnessing potential, rather than considering natural ventilation solutions as an afterthought as in most existing building designs. This improvement would result in more energy efficient buildings, higher occupant productivity, and lower absenteeism rates.