Currently, most detached houses in Japan are airtight wooden structures that have a high risk of vapor condensation in the wall cavities. Vapor condensation in insulation material is a primary contributor to mold growth in wall cavities. Indoor mold concentrations depend not only on indoor mold sources, but also on infiltration from concealed spaces, such as beam space and crawl space. The air pollutants infiltrate houses from these spaces by indoor decompression via the ventilation system, and mold that infiltrates through the glass wool used for heat insulation may remain and grow on the material. In order to measure the mold concentrations in glass wool, a new method is required for air cavity sampling. A method using a Teflon tube inserted into thin spaces in wall cavities or crawl spaces is useful for accomplishing this task. The surface of Teflon is very smooth, but mold adheres to it because of friction or static electricity. The objectives of the present investigation were to develop a method to measure mold concentration using Teflon tubes and to characterize the movement of mold spores between heat insulators.
The following conclusions were obtained from this study:
(1) The mean rates of mold retention in 0.3, 0.5, and 1.0 m Teflon tubes, which were washed three times with sterilized physiological salt solution, were 5%, 21%, and 37%, respectively. This indicated that retention rates increase with increases in Teflon tube length, and it was concluded that a useful sampling method for concealed spaces must use a Teflon tube that is about 0.3 m long, given the retention rate. Data from inter-laboratory testing indicated that a Teflon tube that is 1 m long is unsuitable for this sampling method.
(2) The amount of mold spores in the glass wool heat insulator decreased the more it was washed using sterilized physiological salt solution to clarify the movement of mold spores. After the third wash, the desorption rate of mold spores in the glass wool was about 85%, showing that three rounds of washing were required to measure the mold movement.
(3) Measurement of the movement of mold spores inside the heat insulator showed that the quantity of mold spores adhering to the heat insulator decreases exponentially with an increase in length of the Teflon tubes.
(4) In this range of the wind velocity, the movement of mold spores between insulators through the heat insulator is not significantly influenced by wind in the small chamber.
(5) The experimental results indicate that the quantity of mold spores displaced from the heat insulator by air transportation was not significant.
