The people with unconventional ideas are actually the most creative ones. The original meaning of "window" is "a hole in the wall", but in 1919, someone wanted to expand the glass windows infinitely and even replace the entire wall. This person was German architect Mies van der Rohe, one of the four most famous modern architects in the world in the mid-20th century. In 1921, Mies turned his imaginative idea into a model - the entire outer wall of the building was made of glass, which he called the "Glass Building". He declared that he wanted to merge the window and the wall into one, and the glass outer wall would be both a transparent window and a solid wall.
Mies's "Glass Building" was just a concept. In 1971, the famous Chinese-American architect I.M. Pei finally turned Mies's idea into reality, building the 60-story Hancock Tower in Boston, USA. This entirely transparent building with a mirror-like exterior wall instantly became a sensation in the United States and around the world. The glass outer wall was called the curtain wall, and Mies was hailed as the father of the curtain wall.
However, the good times did not last long. The praise for the Hancock Tower soon turned into criticism. The building's glass curtain wall used 10,344 pieces of 1.4×3.5 meter glass, but more than 2,000 pieces broke within just three years! The beautiful high-rise building was riddled with cracks. This was because the strength of the glass was not enough, and the strength of the steel frame supporting the glass was also insufficient. After five years of renovation, the Hancock Tower finally healed the "scars" on its outer wall.
In recent decades, with continuous improvement, the quality of glass curtain walls has significantly improved: first, "tempering". The glass treated by tempering (heat treatment) has an impact resistance 3-5 times higher than ordinary glass, and even if it breaks, it only breaks into small pieces without sharp edges. Second, "hollow". Making the curtain wall glass double-layered (or even triple-layered) and filling the space between the two pieces of glass with dry air or inert gas can greatly improve the insulation, heat insulation, and soundproofing performance. According to measurements, when the outdoor temperature is -10℃, the temperature in front of a single-layered glass window is -2℃, while the indoor temperature with triple-layered hollow glass is 13℃. It should be emphasized that the air filled in the hollow glass must be dry, to prevent water vapor from condensing on the inner layer in winter and affecting transparency. Third, "double silver". Two extremely thin silver films are coated on the glass. This "double silver glass" can transmit visible light well but reflect solar heat radiation (infrared rays). In the hot summer, double-layered double-silver hollow glass can transmit 90% of visible light and block 90% of solar radiation heat.
The improved glass curtain walls are brand new and very popular, with a "stunning appearance inside and out". From the outside, tall buildings seem to be wearing a beautiful glass coat; when entering the building, the light is transparent, and everywhere is a "big screen", with the scenery outside the window fully in view. During the day, the interior is bright, greatly reducing the use of artificial lighting electricity; at night, the glass curtain wall is transparent, and the building becomes a "crystal palace", with another fascinating view of the city that never sleeps illuminated by lights.
Due to the advantages of glass curtain walls in architectural design, they quickly became popular worldwide. Manhattan in New York, Ginza in Tokyo, Causeway Bay in Hong Kong, and Lujiazui in Shanghai have all become gathering places for glass curtain wall buildings. Although glass curtain walls only entered China in 1984, in just over 20 years, China has become the world's top "glass curtain wall powerhouse": the area of glass curtain walls has soared to 200 million square meters, accounting for 85% of the world's total; China's output of curtain wall glass accounts for 75% of the world's total. In Shanghai alone, there are more than 3,000 buildings clad in gorgeous glass curtain walls.
However, glass curtain walls also have their drawbacks: first, although the quality of glass has greatly improvedHowever, it cannot completely eliminate the phenomenon of self-explosion. To avoid the "glass rain" falling from the sky and injuring pedestrians, green belts are usually set up around glass curtain wall buildings. Secondly, the reflection intensity of glass curtain walls is about 10 times that of ordinary decorative materials, and the resulting "light pollution" can harm human health. Therefore, it is stipulated that residential buildings and school buildings are not allowed to use glass curtain walls.