The inclusion of a ventilated airspace within a wall has been shown to improve the moisture transport of the wall assembly. Experimental data describing the airflow within such a cavity are available for a limited range of weather conditions and geometric configurations, but general relationships between the ventilation within the wall and external weather variables are not. Therefore, a series of steady-state numerical models was constructed to explore the influence of weather variables, including wind speed, insolation, and outdoor air temperature, for brick rain screen wall configurations. These configurations included multiple cavity depths and vent sizes. All models were based on a single-story building height with wind perpendicular to the wall. The results were used to develop a number of correlations intended to supplement the accuracy of transient hygrothermal models.