What are glass curtain walls made of?
Shining, modern and beautiful glass buildings are a sight in big cities. Who invented the exterior walls of buildings like this?
Whimsical people are actually the most creative people. The original meaning of window is "a hole in the wall." In 1919, someone wanted to expand the glass window infinitely, or even replace the entire wall. This man is the 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 made a model of his whimsical idea - the entire building's exterior walls were made of glass, calling it the "Glass Building." He claimed that the window and the wall would be combined into one, and the glass exterior wall would be both a transparent window and a solid wall.
Mies's "Glass Building" was just an idea. In 1976, the famous Chinese-American architect I.M. Pei turned Mies's idea into reality and built the 60-story Hancock Tower in Boston, USA. This is a skyscraper with a glass exterior wall. This novel building, which is completely transparent and has a mirror-like exterior wall, is eye-catching. It immediately caused a sensation in the United States and the world. The glass exterior wall is called the glass curtain wall, and Mies is known as the father of the glass curtain wall.
However, the good times did not last long, and the praise for the Hancock Tower quickly turned to criticism. In just 3 years, more than 2,000 yuan has been shattered! Beautiful tall buildings are riddled with holes. That's because the glass isn't strong enough, and neither is the steel frame that supports the glass. After five years of renovations, the "scars" on the outer wall of the Hancock Building were finally healed.
In recent decades, through continuous improvement, the quality of glass curtain walls has been significantly improved: First, "tempered". The impact strength of tempered (heat-treated) glass is 3 to 5 times higher than that of ordinary glass, and even if it breaks, it only breaks into small pieces of glass without sharp angles. The second is "hollow". Making the curtain wall glass double-layered (or even triple-layered), and filling dry air or inert gas between the two pieces of glass can greatly improve the thermal insulation, heat insulation, and sound insulation properties. According to measurements, when the outdoor temperature is -10°C, the temperature in front of the single-layer glass window is -2°C, while the indoor temperature using triple-layer insulating glass is 13°C. It should be emphasized that the air filled into the insulating glass must be dry to prevent water vapor from condensing on the inner layer in winter and affecting the transparency. The third is "double silver". Two extremely thin silver films are coated on the glass. This "double silver glass" can transmit visible light well but reflect the sun's thermal radiation (infrared rays). In the hot summer, double-layer double silver insulating glass can transmit 90% of visible light and block 90% of solar radiation heat.
The improved glass curtain wall has a new look and is very popular, with "infinite scenery inside and out". From the outside, the high-rise building seems to be wearing a beautiful glass coat; when you walk into the building, the light is transparent, there are "big screens" everywhere, and you can have a panoramic view of the infinite scenery outside the window. During the day, the interior is bright, which greatly reduces the electricity consumption for artificial lighting; at night, the glass curtain wall is completely transparent, and the building becomes a "Crystal Palace", giving you another charming view of a brightly lit city that never sleeps.
Because of these advantages in architectural design, glass curtain walls quickly became popular all over the world. Manhattan in New York, Ginza in Tokyo, Causeway Bay in Hong Kong, and Lujiazui in Pudong, Shanghai have all become places where glass curtain wall buildings gather. Although glass curtain walls only entered China in 1984, in just over 20 years, China has become the world's number one "glass curtain wall country": the area of glass curtain walls has soared to 200 million square meters, accounting for 85% of the world's total; China's curtain wall glass production accounts for 75% of the world's. Shanghai alone has more than 3,000 buildings with gorgeous glass curtain walls.
However, glass curtain walls also have shortcomings: first, although the quality of glass has been greatly improved, it cannot eliminate the phenomenon of self-explosion. To prevent "glass rain" from falling from the sky and injuring pedestrians, green belts are usually set up around glass curtain wall buildings; second, the reflection intensity of glass curtain walls is about 10 times that of ordinary decorative materials, and the resulting "light pollution" will cause harm to human health. Therefore, it is stipulated that residential buildings and school buildings shall not use glass curtain walls.
