This study examines the ventilation function and economic feasibility of a combined air-diffuser ventilation (CAV) system, in which the exhaust air opening and the supply air opening are combined into a single module. A mock-up test and computational fluid dynamics (CFD) were employed to identify the properties of the CAV. The CFD was validated using a benchmark test and then used to investigate the ventilation function of a conventional ventilation system and the CAV using SVE3 and SVE6 for ventilation. The SVE3 and SVE6 results of the CAV were similar to those of the conventional ventilation system. The economic feasibility was assessed based on the duct length and the number of components. In comparison to the conventional ventilation system, the duct length decreased by approximately 68%, the number of dampers decreased by 50%, and the number of diffusers decreased by 40-50% for the CAV.