Development of simple semiempirical models for calculating airflow through hopper, awning, and casement windows for single-sided natural ventilation

Natural ventilation is a promising approach to reducing building energy use if designed properly. Most of the previous design models for calculating airflow due to single-sided natural ventilation have been based on the assumption of simple openings. Since, most windows are not simple openings, but rather can create flow obstructions when opened; the impact of window structure on ventilation needs to be accounted for in order to accurately predict the ventilation rate in buildings. This paper presents an experimental and numerical evaluation of the impact of three types of windows - hopper, awning, and casement - on airflow in the case of single-sided natural ventilation. Semiempirical models for predicting the ventilation rate were developed for these window types and validated by both large-eddy simulations and full-scale measurements. In general, the predictions agreed with the measured results within an error of 25%, and the new models can be used for the design of natural ventilation systems.