This paper presents a study of room cross-ventilation airflow. A simplified model is developed using scaling analysis, experimental correlations, and computational fluid dynamics. The model distinguishes two regions in the room, the main jet region and the recirculations, and models relevant flow features that are essential inputs when predicting heat and pollutant transfers as well as indoor thermal comfort conditions. The results of the model are a set of formulas that predict the airflow rates and characteristic velocities in the jet and recirculation flow regions. The formulas clearly display the first order effects of room geometry on cross-ventilation airflow characteristics. Simple examples of application of the model to cross-ventilation design are presented.