Natural ventilation in buildings can improve indoor air quality and thermal comfort and reduce airconditioning use except for highly polluted area. Traditionally, the inflow boundary conditions for calculating natural ventilation used weather data from a meteorological station that is often in a suburb. The use of hour-by-hour wind velocity from the station may give rise to some errors because of the large time step. This investigation proposed a correlation method for converting the hour-by-hour wind velocity from a meteorological station to minute-by-minute velocity, using data measured on the rooftop of the building of interest. A CFD simulation with the coupled modeling method using the unsteady RNG k-epsilon model was performed to calculate airflow around the building and airflow in an apartment simultaneously. The computed outdoor wind velocity and indoor ventilation rate were compared with the corresponding experimental data. The results showed that the simulations calculated the outdoor wind velocity on the building rooftop and the cross-ventilation rate through the apartment with acceptable accuracy. (C) 2019 Elsevier B.V. All rights reserved.