Assessment of year-round wind-driven ventilation by an integrated ventilation model

Abstract

This study integrates a physical model for cross ventilation and empirical formulae for single-sided ventilation to predict wind-driven ventilation of buildings. The prediction model uses reduction factors to account for the different effects of wind direction, window type, nearby buildings, and building length. The predicted ventilation rates are validated by the results of wind tunnel experiments, a CFD model, and the airflow network model in the EnergyPlus model. The integrated model is then utilized to realistically assess the natural ventilation of a residential building under varying wind speeds and directions throughout a year. The simulation results demonstrate that double-sided cross-ventilation can achieve a ventilation rate roughly 20 times larger than single-sided ventilation under the same wind speed and opening area. In addition, the EnergyPlus model underestimates the annual average ventilation rate by neglecting the shear-induced ventilation when the prevailing wind direction is parallel to the building openings. The change of prevailing wind direction in different seasons can have a substantial effect on the ventilation rate, especially when the external openings of the building are limited to certain sides. Thus, the assessment of natural ventilation of a building must take into account the building orientation and seasonal variation of natural wind conditions.