Study on humidity environment in crawl space of dwelling house.

Many houses in Japan have crawl space between the lowest floor and the earth ground which is about 50 cm in height. This is considered as protection against corrosion of wood materials in the floor. Japanese building codes recommend ventilation with outdoor air in this space. In our field research, we found condensation in the crawl space in summer. This is due to low temperature of the ground and high humidity of the outdoor air which is typical of the Asian climate. To prevent this condensation and ensure long-term durability, we estimated the effect of a humidity-controlling soil cover which absorbs moisture into itself and desorbs during the dry season. The estimation is performed by field experiments and numerical analysis based on simultaneous heat and moisture transport process, which is validated by experimental results. The numerical analysis also clarifies the effect of ventilation.