Study on Performance Evaluation of Mechanical Ventilation Systems for Occupied Houses

In the first phase of the current project, the ventilation rates of occupied houses in the northern region of Japan were investigated from 2001 to 2005. It was revealed that, despite installing mechanical ventilation system, low ventilation rate was found in many houses. The causes were believed attributing to lack of cleaning of grills, filters and insect protection meshes. The second phase of the project was to investigate the causes and resolve the problems. This project was started in 2005 and 12 houses installed with mechanical ventilation system were investigated. The investigation included measurement of airflow rates at inlet/outlet by using airflow meter, observation of dust conditions in filters and questionnaire survey about the condition of usage and maintenance of the ventilation system. This study found that some of the ventilation systems were not properly operated and airflow rates were insufficient in almost all houses because the dust was accumulated on the filters as airflow rate at inlet/outlet increased after the filter was cleaned. Only very few occupants cleaned the filters regularly as reported in questionnaire survey. The investigation confirmed that airflow meter is a convenient and efficient method to measure airflow rate, particularly for the occupied house. It is thus recommended that periodic measurement using airflow meter should be carried out to monitor the airflow rate