TITLE:
Infiltration of Mould from Crawl Space under the Prefabricated Bathroom
AUTHORS:
Motoya Hayashi, Haruki Osawa, Kenichi Hasegawa, Yoshinori Honma, Hiromi Yamada
KEYWORDS:
Mould, Infiltration, Air Tightness, Crawl Space, Tracer Gas
JOURNAL NAME:
Journal of Environmental Protection,
Vol.5 No.10,
July
30,
2014
ABSTRACT: The indoor mould concentration depends not only on the outdoor mould
source but also on the indoor mould source. The mould source is not only on the
interior surface but also in the concealed spaces: a crawl space, a beam space,
a wall cavity etc. Most detached houses in Japan have crawl spaces under the
first floor. The humidity is high from spring to autumn in crawl spaces.
Therefore the concentration of mould spore is very high in most crawl spaces.
Prefabricated bathrooms called “bath-units” are installed in most Japanese
houses. The authors showed in the previous studies that there are infiltration
routes between bath-units and walls that the routes may lead chemical compounds
from crawl space to indoor space. In this study, the influence of mould
infiltration from crawl space upon indoor mould concentration is investigated using
a test house which consists of a lavatory and a bathroom. The structure of the
house is wooden post-and-beam. The house is airtight and insulated according to
the latest building code for save energy. The mould concentrations were
measured in the crawl space and the indoor spaces continuously using a mould multi-sampling
system with a pump, valves and impingers. Before the measurements, the indoor
mould concentration was made low using an air cleaner. The air flow rates were
measured using tracer gases. After the exhaust fan was switched on, the mould
concentration increased. The number of infiltrated mould was calculated using
air flow rates and mould concentrations. The results showed that mould
infiltration ratio may be one of the important indicators of indoor air
quality.