Estimating natural ventilation potential for high-rise buildings considering boundary layer meteorology

The design of energy conservative buildings that incorporates natural ventilation (NV) strategy has become increasingly popular around the world. Natural ventilation is a key solution for reducing energy consumption of buildings and for maintaining a healthy indoor environment. However, the adoption of natural ventilation in high-rise buildings is less common. As rapid population growth and urbanization take place in cities, it is important to explore the substantial energy saving potential of high rises by utilizing natural ventilation. In this study, we have provided the early effort to estimate quantitatively the vertical profiles of NV potential for high rises at major cities from six climate zones in the U.S. (i.e., Miami, Houston, Los Angeles, New York City, Chicago, and Minneapolis), using an in-house boundary layer meteorology model. The diurnal cycle of atmospheric boundary layer (ABL) and local climate characteristics are found to have a great effect on the vertical structure of NV potential. In general, negative vertical gradients of NV hours are observed for all cities except Miami where the vertical distribution is nearly uniform. For example, the annual NV hour decreases from 7258 at ground level to 4866 at 300 m above the ground in Los Angeles. Our analysis shows that outdoor temperature is a key meteorological parameter that determines vertical profiles of NV hours in New York City, Los Angeles, Chicago, and Minneapolis. In contrast, humidity plays a greater role in cities like Miami and Houston where the outdoor temperature is often favorable for using natural ventilation except in the summer. Among studied cities, Los Angeles provides the ideal climate (warm and dry) for utilizing natural ventilation, displaying the greatest NV potential (7258 NV hours or 83% time of the year at ground level), followed by New York City with 3360 NV hours. The remainder of the four studied cities display comparable numbers of NV hours of approximately 2500 at ground level. The methodology and findings from this study are intended to assist architects and policy makers in quantifying the potential energy savings of natural ventilation, and illustrating the importance of considering the vertical variations of elevated thermal environment in high-rise buildings across different climate zones in the U.S.