National survey on ventilation system and occupants’ health in japan

The indoor environment and occupants’ health of approximately 5,000 residential buildings were investigated by a questionnaire covering entire Japan. The purpose of this survey is to clarify the association between indoor air pollution and adverse health effect, and to study effective ways of keeping indoor air clear with ventilation systems in house. Questionnaires were distributed to 7,812 occupants living in a house with a mechanical ventilation system across 47 Prefectures in Japan on February 2012 using internet survey web site. The questionnaires were completed and returned within 5 days by occupants. The contents of the 50-question survey addressed the indoor environment, installed equipment, the type of ventilation system, occupant behaviour, shelter performance of the building, occupant characteristics, health related QOL (SF8 Health Survey Japanese version provided by Institute for Health Outcomes & Process Evaluation Research) and health problems such as respiratory symptoms, allergic diseases and chemical sensitivities. As a result, the total number of respondents was 5,265 and the response ratio was 67.4%. Also the actual conditions of both the perception of thermal environment, dryness, wetness and air quality and house characteristics such as thermal performance on envelopes, heating system and ventilation system have been clarified, and several problems related to using ventilation systems have been grasped.  
This paper described the outline of investigation and the results obtained from the questionnaire survey. In particular, the features of the home environment and occupants health conditions with health related QOL were shown and the association between indoor dampness such as mould growth and ventilation system were discussed through a multivariable regression analysis. This survey revealed the ratio of the type of an installed ventilation system and the pattern of using it in Japan and the possibility of the association between adverse health effect and indoor environmental factors such as inadequate ventilation.