It is very important to keep indoor air quality good in order to avoid health problems such as Sick House Syndrome occurred in Japan. It is also very important to ventilate indoor spaces efficiently to reduce energy consumption and CO2 emission. Ventilation efficiency indexes have been proposed as means to evaluate the efficiency of ventilation systems and these indexes have been taken into account in ventilation design. The previous paper proposed the effective ventilated volume, hereafter EVV, as a ventilation efficiency index and showed a definition of EVV based on the volume integral with a weighting function. The meaning of EVV depends on the selected weighting function, therefore three types of weighting function were examined. In this paper, several case studies on the EVV based on computation fluid dynamics (CFD) are demonstrated. In the cases of office models and factory models, mixing ventilation and displacement ventilation are compared with EVV results. In the house kitchen models, the ventilation efficiency is examined with various positions of supply opening of outdoor air. In the house models, two conditions are studied. EVV is evaluated when 24 hour ventilation system is operated and when the kitchen exhaust system is operated. In the clean room models, the position of exhaust openings is examined. When the exhaust openings are installed at ceiling, calculated EVV is much higher than that in the case of wall exhaust openings.