MEASUREMENT ON INFILTRATION OF CHEMICALS FROM CONCEALED SPACES IN WOODEN DETACHED HOUSES

Abstract

The aim of this study is to keep indoor air quality well considering the infiltration of chemicals from concealed spaces in detached houses. The building standard law was revised to prevent sick house syndrome in 2003. The use of continuous ventilation systems, the prohibition of chlorpyrifos, the control of the emission rate of formaldehyde and the countermeasure toward the infiltration from the concealed spaces like the ceiling space have been regulated after this revision. In this study, the infiltration characteristics of VOCs from the concealed spaces, were investigated using the measurement data of 8 new wooden houses with exhaust ventilation systems or exhaust and supply ventilation systems in Saitama prefecture. The structurer and building materials of these houses are general in Japan. The structures of these houses were wooden post and beam structures. The floor is made with plywood and flooring. The wall is made with plasterboard and vinyl cloth/plaster finishing. The ceiling is also made with plasterboard and vinyl cloth/plaster finishing. The results showed the followings. 1. The indoor emission rates and the infiltration rates from the concealed spaces can be calculated from airtight levels of houses, ventilation rates, VOCs concentrations when the ventilation system is used and when the air is exhausted. 2. The equivalent leakage area of houses were 0.5～3.0 (cm2/m2). The decompression levels were -5.3～6.0 (Pa) when the ventilation systems were used and 9.7～60.3 (Pa) when the air is exhausted. 3. The indoor VOCs concentrations when the air is exhausted were higher than the VOCs concentrations when the ventilation systems are used in most houses. 4. The infiltration rates were significantly higher than the indoor emission rates not only in houses with the exhaust ventilation systems but also in houses with the exhaust and supply ventilation systems. 5. The indoor VOCs concentrations increases with the indoor decompression level. These studies showed that the indoor VOCs concentrations depend on the infiltration rates from concealed spaces in new houses in Japan. Therefore, the countermeasure toward the infiltration from the concealed spaces and the control of air quality in the concealed spaces, are still important.