Commercial wind towers have been the focus of intensive research in terms of their design and performance. There are two main forces which drive the flow through these devices, external wind and buoyancy due to temperature difference. This study examines the relationship between these two forces and the indoor ventilation rate achieved. The work uses computational fluid dynamics (CFD) modeling to isolate and investigate the two forces and draw comparisons. The study found that as expected the external driving wind is the primary driving force providing 76% more internal ventilation than buoyancy driven flow, which is deemed secondary. Moreover the study found that the effect of buoyancy is insignificant without an external airflow passage other than the wind tower itself. The addition of an external airflow passage such as a window in combination with buoyancy force increased the indoor ventilation by 47%. Therefore the careful positioning of windows in conjunction with internal heat source has the potential to overcome the lack of external wind driven forces in dense urban environments. (C) 2011 Elsevier B.V. All rights reserved.