A holistic approach to natural ventilation studies

Abstract

Natural ventilation in buildings can increase thermal comfort and reduce air-conditioning use. However, it is very challenging today to accurately determine the natural ventilation rate through a building. This paper outlines a method to calculate the wind distribution around a building site from information obtained at a meteorological station miles away. This paper also discusses the influence of surrounding buildings on the wind flow around a target building at the site, and presents various geometrical models. In addition, the use of hour-by-hour wind velocity typically available from a meteorological station may give rise to some errors because of the large time step. A correlation method can be employed to convert the hour-by-hour wind velocity to minute-by-minute velocity. One can then use CFD to calculate the airflow around the building and wind-driven cross ventilation through an apartment simultaneously. However, prediction of single-sided natural ventilation is difficult because of the bi-directional flow at the room opening and the complex flow around buildings. This paper presents an empirical model that can predict the mean and fluctuating ventilation rates due to the pulsating flow and eddy penetration of wind-driven single-sided ventilation in buildings with three types of windows. One must use the correct strategy in a building in order to achieve the maximum benefits of natural ventilation.