Computational Fluid Dynamics numerical analysis is performed to investigate the ventilation performance and the internal thermal environment of naturally ventilated buildings. Several alternative scenarios are generated by varying the size of openings with different configurations of orientation and solar shading. Modifications have been made among different models based on revisions of windows' wall ratios of inlets and outlets to identify the most effective window design that maximizes wind-driven natural cross-ventilation. The study further investigates the feasibility and usage period of natural ventilation to reduce the buildings' cooling energy demand in hot humid climate. In general, the results show that cross-ventilation may offer significant potential to improve the indoor thermal environment and comfort conditions to acceptable levels. During the summer season, high outdoor air temperature and the low wind conditions may not be adequate to provide internal air movement to satisfy all the cooling requirements and to ensure thermal comfort, but indoor temperature reductions of 4–8°C are possible. Data also show that the airflow rate and the indoor temperature are directly proportional with the size of inlets and outlets. Higher flow rates occur with large inlets and outlets that have proper orientation as regards prevailing wind.