Natural ventilation comprises various systems such as infiltration and exfiltration (for example, through cracks, leakages), window ventilation, as well as shaft ventilation. A considerable number of buildings rely exclusively on natural means for ventilation. This underscores the importance of natural ventilation systems for indoor air quality. Nevertheless, few generally accepted design rules and codes are available to assist the designer in the task of dimensioning and control of natural ventilation systems. The successful performance of most natural ventilation systems rely on occupants' behavior. However, the computer-aided simulation of the performance of these systems could support the designer in creating the necessary framework for appropriate behavioral patterns. This could be achieved through properly dimensioned, constructed, and located window and shaft systems while responding to specific geometrical configurations and climatic situation of the building as well as to the health- and comfort-related occupancy requirements. Based on mathematical modeling and long-term empirical studies of residential buildings in Austria, a simulation model was developed to predict the air flow rates and, thus, the air exchange rates between indoor rooms and exterior environment. The comparison of the field measurements with the corresponding simulation results showed an encouraging correlation.