Field Survey on Air-tightness, Ventilation Rate and Indoor Air Quality of 77 Houses in Japan

In order to determine the causes of SHS (Sick House Syndrome), a field survey on indoor air quality and health conditions of occupants has been conducted for 8 years in 77 detached wooden houses in Japan. The result of this survey had been reported partly in the proceedings of Indoor Air 2008 (Yoshino et al., 2008). In most these houses, we have measured the level of air-tightness and ventilation airflow rates. For some houses, the air-tightness level and ventilation rate were measured several times within a few years. This paper reveals the relationship between the level of airtightness, ventilation rate and indoor air quality in buildings. The results found are: 1) equivalent leakage area of the buildings distributed from 0.4 to 12 cm2 per unit floor area; 2) It is thought that the major causes of that the level of air-tightness is different between houses are the buildings completion year and the age of house. About the year of completion of the house, the air-tightness tends to be higher for new houses. For the age of house, as the buildings becomes older, air-tightness of house tends to be lower; 3) In some houses, the formaldehyde and TVOC concentration were decreased after either, installing a new mechanical ventilation system or increasing the airflow rate by changing to higher fan speed mode of the existing ventilation system; 4) In many houses with equivalent leakage area of less than 5 cm2/m2, the concentration of HCHO was higher than the guideline value. But in the houses with 0.5 air change rate provided by mechanical ventilation system, the concentration in most houses was lower than the guideline level.