Abstract
The term "hour shadow" in the title means an area bounded by a shadow curve of n-hours and a portion of walls of a building. In this paper the author deals with two problems of "hour shadow". One is the relation between the plan of a single straight block and the critical height of the block. The critical height of the building means the following; An increase of height of the building produces an enlargement of the area of "hour shadow" up to a certain point, beyond which any further increase produces no further change in the area of "hour shadow" upon the ground. Another is the relation between proportions of the building and the area of "hour shadow". In any case dealt here, the long axis of a single straight block runs north and south, or east and west. Moreover, the shadow curves in this study are made from shadows cast by a building at the winter solstice in Tokyo (Lat.35°41'N). The results are as follows. (1) The critical height of the building is decided by aspect ratio of the plan. (2) The area of "hour shadow" of the building is decided by both aspect ratio of the plan and ratio of slenderness of the elevation.
