The purpose of this study is to investigate operable controls and energy saving potentials of an 100% outdoor air system integrated with indirect and direct evaporative coolers in eleven major cities in South Korea. It was assumed that three zones in a university campus building are served by the two different HVAC systems; a variable air volume system(VAV), and a 100% outdoor air system integrated with indirect and direct evaporative coolers. After establishing operable control strategies, energy saving potentials of each system were estimated using a simulation model representing each HVAC system. It was found that the proposed system can reduce the cooling and heating coil loads over 30% to 60% annually compared with the VAV system. It was also found that the energy saving potentials of the evaporative cooling based 100% outdoor air system is not very sensitive to the regional weather conditions.