Natural ventilation has generally remained the preferred choice for improving thermal comfort and saving energy related to the built environment. To best represent the performance of natural ventilation, the style of windows used to exchange indoor and outdoor air become rather important. However, the knowledge of real window behavior is still extremely limited, especially in terms of natural ventilation driven by the combination of buoyancy and wind forces. Therefore, this study investigated single-sided natural ventilation driven by buoyancy and wind through variable windows. The Reynolds-averaged Navier-Stokes (RANS) model and k-omega turbulence model were applied to solve airflow characteristics inside and outside the building, and the ventilation rates for various windows produced by the combined forces were compared using computational fluid dynamics (CFD) and proper orthogonal decomposition (POD) methods. The results revealed that the ventilation rate generally increased with increasing wind speed, except for several specific windward conditions where buoyancy and wind presented as counteracting forces. The dominant force in the combined buoyancy and wind-driven ventilation was highly impacted by wind speed and direction. According to the comparison of indoor thermal profiles for various window cases, natural ventilation driven by different forces presented obvious differences although the open areas of windows were identical. Therefore, recommendations are provided for implementing specific window configurations that are compatible with different weather conditions in practice. (C) 2018 Elsevier B.V. All rights reserved.