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| Central Shanghai, 2010. |
A recent article in the China Daily relates a disturbing new phenomenon in several Chinese cities directly related to the rapid pace of growth. Due to deficiencies in the manufacturing, installation, or maintenance of glass curtain wall systems, some glass has been reported to shatter and fall, sometimes from great heights. These 'glass bombs' have injured and killed several people, and in the case of Shanghai, they have led to an outright banning of the extensive use of glass curtain wall systems in the city. Ones first reaction may be to wonder whether that's going too far given the ubiquity of glass as a modern building material. In fact how would this affect the look of the city?
While the Newtonian embodied energy of glass may be on display in the spontaneous shattering of windows, the energy embodied in glass by the process of manufacturing may be a more compelling—if hidden—reason to limit it's use. While not the highest embodied energy material (this distinction goes to steel and aluminum, which are also required elements in a curtain wall), the manufacturing of glass requires roughly 10 times as much energy as one of the most common construction materials in China: concrete. The figure comes out to about 12-25 giga-joules of energy for 1 metric ton of glass. (1 joule = 2.7778×10-7 kilowatt-hours)
