In this study, the houses in the northern region of Japan had been investigated. The investigation included the measurement of the ventilation rate using three different methods, via the constant concentration method, measurement of airflow at inlet/outlet and PFT method. This paper shows the relationship between the measurement results of ventilation rate via these three measurement methods. It is found that the amount of outdoor air introduced was insufficient in many houese and some ventilation systems are not operated properly. The relationship between the measurement results of ventilation rate via the three different measurement methods is clarified in this study.
