The purpose of this research is to clarify psychological effects of windows and to confirm the way they compensate other interior elements. Many elements were introduced in an underground experimental space, then postoccupancy evaluations came into effect by the subjects studied there. 1) The transition of wind or light, and outside information such as the time or weather, are more important for recreational purpose rather than for research activities. 2) Principal psychological effects of windows are pleasantness, including recovery of mental fatigue, reduction of monotonousness, creating a good atmosphere, and connection with the outside world. There is a good possibility that the effects of windows are compensated by other elements too. 3) It is possible that a space without a window makes the occupants feel more at ease and improves concentration for their research activities than a space with a window.
