"A space dimension often feels different from the actual volume when a person perceives the space. This can be considered because a person is estimating the extent of a space not only from the dimension of a space simply but also from other factors composing it synthetically. This is defined as Spaciousness. Originally Spaciousness is translated the Japanese word "Kaihokan", which means something between the 'feeling of liberation' and the 'sensation of being open'. Much discussion led to the conclusion that 'spaciousness' was the single English word closest in meaning. At first, Prof. Inui introduced Spaciousness in 1970s[1]. The equation for Spaciousness was given from the result of evaluation experiments with scale models. The variables finally adopted to equations were sky luminance, interior illuminance, room size?a ratio of width and depth, and window width. Though there are some studies for Spaciousness since then, it is difficult to apply findings of those to the small space because most of those were about the large space like an open office."