An ancient Japanese well-known essayist, named Kenko, a Buddhist priest, wrote the “Essays in Idleness,” which is called “Tsurezure-gusa” in Japanese. Section 55 of these essays says, “ A house should be built with the summer in mind. In winter it is possible to live anywhere, but a badly made house is unbearable when it gets hot.” Even in modern days, this section is often referred to since it eloquently describes the unbearable hot and humid climate of Japanese summer as well as the Japanese housing conditions. In short, the Japanese traditional houses had such characteristics as having long eaves to prevent sunshine of summer from coming into rooms, or being equipped with large open passages with sliding-wooden-doors for cross-ventilation utilization. However, there is less outdoor wind blowing into the building due to increased density of buildings in urban areas in Japan and Southeast Asia over the past several years. As a result, there is no sufficient amount of wind in the indoor. Additionally, due to concerns of security and privacy, houses with many or large size of openings are difficulty to be built. Despite the above mentioned factors that discourage utilization of cross-ventilation, residents still desire to have more natural airflow in the house based on the results from questionnaire survey (see Sects. 4.2 and 4.3 for details). Therefore, it is important to develop a design that improves amount of airflow. Shiraishi et al. (2002) demonstrated that the cross-ventilation flow