In Taiwan, the indoor environment of factories can be classified into precisely controlled environments, austere environments, and eclectic environments. Compared with the precisely controlled environments of the electronics/medicine industries, eclectic environments of such traditional industries as footwear, textiles, or light metal processing generally use forced ventilation instead of HVAC systems to improve indoor thermal comfort. In this study, the design strategies of negative pressure fans in a large-span factory were studied, and 0.6-3.0 m/s was defined as the effective wind speed range via thermal comfort index for evaluating improvement. We first carried out an experimental study to determine an effective distance of fans, and the results were used to validate simulation via computational fluid dynamics. A simulation study was then carried out to study the design strategies of fan installation in factories with 30 m spans. The results showed that the simulation model fit the experimental data well in the first stage and that 15 m was the best distance for installing an auxiliary fan in all cases with various inlet wind velocities. In the simulation studies, the results demonstrated that the effective wind percentage can be improved 40%~60% through proper design, which provides significant potential for energy-saving and thermal comfort in traditional factories.