Ventilation performance depends on room geometry, ventilation method and operating conditions, as well as on the location, source strength, and types of contaminants. A menu-driven ventilation model was developed that can determine the turbulent flow field and time-dependent/steady-state contaminant concentration distributions within an isothermal indoor space. This two-dimensional turbulence model was developed specifically for personal computers. The flow field calculated from the model showed good agreement with results from the commercially available FLUENT code. Ventilation performance was evaluated using the scale, 'Ventilation Performance Index.' Effects of room configurations, operating conditions, and effective diffusion coefficient on ventilation performance were investigated by varying a Peclet number.