In the middle and high latitudes of the northern hemisphere, the sun is almost always in the southern sky (north of the Tropic of Cancer, south of the Arctic Circle, northeast at sunrise and northwest at sunset). Sitting in a cube (assuming it faces south) can get sunlight on all sides (except the bottom).
Some places (such as China monsoon region) are also related to the wind direction.
China is located in the mid-latitude and low-latitude areas of the northern hemisphere, which is determined by this natural geographical environment. Houses facing south can attract sunlight in the leeward in cold winter, avoid the dominant wind direction in winter, and avoid excessive heat loss and affect the indoor temperature. In summer, the wind is very cold. Sitting in a house facing south, it is warm in winter and cool in summer, with plenty of light. Even in winter, sunlight can shine into the depths of the room, making people feel bright and warm. In addition, ultraviolet rays in the solar spectrum can sterilize and improve indoor sanitary conditions. In winter, ultraviolet rays are received indoors in all directions, with more in the south direction, southeast direction and southwest direction, and less in the east-west direction, only about half of the south direction. Rooms in the northeast, northwest and north receive less ultraviolet rays, only about one-third of those in the south and southeast. This is because there is little or no sunshine, and only a small amount of ultraviolet rays scattered in the sky are accepted. Therefore, considering the amount of ultraviolet rays received, the range from 45 southeast to 45 west is a better architectural orientation. Moreover, in this living room, in summer, when the sun rises close to the top of the head, the house cannot be exposed to strong sunlight. In addition, the southeast wind can also be blown into the house through windows and portals, making people feel cool and comfortable. Therefore, China's house is mainly located in the position facing north and south, and China people are willing to live in the north room, that is, the house facing south. The order of other directions is roughly southeast, east, southwest, north and west.
Houses facing south are the best choice for other countries in the northern hemisphere, especially Canada, which is located in the high latitude area of the northern hemisphere and is very cold in winter. The house facing south is more suitable for its natural geographical environment.
For the above reasons, sitting north facing south naturally becomes the basic principle of geomantic omen. In geomantic omen, it is often said that there is a dragon on the left and a white tiger on the right. The dragon is auspicious and the white tiger is fierce. This is based on the basic principle of sitting north and facing south. Take the "Kanzhai" with the geomantic omen of Eight Houses facing south as an example. The longevity of Kanzhai and the auspicious position of natural medicine are just on the left Qinglong side, while the desperate situation and disaster are just on the right Baihu side. Sitting in the "out of the house" facing south, Zuo Qinglong is occupied by despair, five ghosts and six evil spirits, and Zuo Qinglong has a long story. Many experts and scholars in geomantic omen believe that only by sitting in the north-south direction can they be called the guardian of Qinglong White Tiger. Other left green dragons and right white tigers only represent left and right positions, not real green dragons and white tigers.