An innovative control strategy for a naturally ventilated (NV) swine finishing building was evaluated. Extensive monitoring of an existing NV-controlled swine finishing building indicated that the building temperature control was .3.C of set-point for less than 50% of the time, with 20% of the time greater than .6.C. Based on the experience gained from this monitoring, the building was modified to accommodate testing and development of a new NV control logic. Using the improved NV control logic, the building temperature was .2.C of the set-point for 91% of the time, and, .3.C for 97% of the time for a wide range of cold and mild weather conditions with no supplemental heater use. A routine using inside relative humidity feedback was used to preserve indoor air quality levels through a series of purging routines.