Summer in Beijing is very hot. Why is the Forbidden City always cool?

Because this is related to the architectural style and building materials of the Forbidden City. The golden roof and purple walls must be the most distinctive ancient buildings in the Forbidden City. If you carefully observe the buildings in the Forbidden City, you will find that these "golden roofs" cover an area much larger than the building itself, and the eaves at the four corners of the roof stand upright like birds with open wings. This design is not just for beauty. The sun at noon in summer will be blocked by the eaves to achieve the purpose of shading and cooling. In winter, oblique sunlight can shine into the palace and drive away the cold. This is because the sun shines at different angles in different seasons.

The roof of the Forbidden City is also very particular about the choice of building materials. The wooden base of the roof of ancient palace buildings is usually covered with a layer of 30 cm thick mud. These mud backs are mainly composed of fender ash, cyan ash, hemp fiber mud and other materials. These materials have good thermal insulation performance, which can absorb a lot of heat from the outdoor and prevent excessive heat from being directly transferred to the indoor.

In the Forbidden City, some important halls also have double-eaved roofs. This structure forms a top floor between the roof and ceiling of the ancient building. This kind of top floor can intercept the direct solar radiation heat on the roof, make the roof become secondary heat transfer and prevent the solar radiation heat from directly acting on the interior of the building. In addition, due to the rising trend of hot air, indoor hot air will rise and accumulate on this raised floor to avoid direct contact with people. On the one hand, the roof blocks sunlight and heat from entering the room directly; On the other hand, because of its good ventilation performance, it can promote the circulation of indoor air and discharge indoor hot air smoothly, which can be described as the best of both worlds.

A good building should not only be well integrated with the external natural environment, but also let the users and residents in the building use and live with confidence.