Investigation of Hygrothermal Control and Architectural Measures to Reduce Mold Risk in RC Detached Houses in Hot and Humid Regions

Mold growth poses health hazards such as allergies and respiratory diseases, making it a major environmental risk in the built environment. In hot and humid regions where high temperatures and humidity persist year-round, substantial indoor-outdoor temperature differentials caused by air conditioning lead to summer condensation and subsequent mold occurrence. For these reasons, the need for humidity control measures in hot and humid regions is increasing. Okinawa Prefecture is the only region in Japan characterized by a hot and humid climate throughout the year. This study proposes methods to mitigate high humidity during the rainy season in highly ventilated reinforced concrete (RC) detached houses located in Okinawa considering "occupant behavior" and "architectural measures." For each proposal, we examined changes in temperature and humidity within the bedroom using multiple room temperature and humidity analysis simulations. We evaluated the mold suppression effect using a mold index and calculated the power consumption of the air conditioner and dehumidifier. Regarding occupant behavior, two approaches to reducing relative humidity were examined: increasing temperature using heating, and lowering absolute humidity using dehumidifier operation. It was demonstrated that both methods reduce the risk of mold growth. Furthermore, it was found that operating heating and a dehumidifier for three hours reduced the risk of mold growth to a similar level, and heating consumed less electricity than the dehumidifier. From the architectural perspective, thermal insulation and airtightness retrofitting is proposed. This proposal significantly reduced the risk of mold growth and lowered power consumption compared to heating operation or dehumidifier use.