History of Green Roof
2015-08-11
Green roofs origin from thousands of years ago. The most famous green roofs were the Babylon's Hanging Gardens. They were constructed around 500 B.C and considered as one of the Seven Wonders of the Ancient World. They were waterproofed with layers of reeds and thick tar and built over arched stone beams. Plants and trees were then planted. In ancient time green roofs was made up of cave like structures or sod roofs covered with earth and plants commonly used for agriculture, dwelling, and ceremonial purposes. These early shelters provided protection from the elements, a cool location in the summer, and good insulation during the winter months. Unfortunately, for modern conveniences, these were neither was there any system to keep out unwanted borrowing wildlife or waterproof.
For the purpose of insulation, people used sod to cover their roof tops. In recent times, it kept their homes cool in summer and warm in winter. Modern green roofs may have had their "roots" in ancient time, but technological advances have made them far more efficient and expensive than their ancient counterparts.
Modern green roofs are made of a system of layers placed over the roof to support soil medium and vegetation. This is relatively new phenomenon and was developed sophisticated irrigation and protection against root ingress for rooftop gardens. Green roofs are also becoming increasingly popular in the United States, although they are not as common as in Europe.
Green roofs mainly have two general categories - intensive and extensive. the difference between this two categories include loading capacities, soil depths and their functions. Extensive green roofs have thin soil depths and less number of soil layers, hence they are less in weight, less expensive and require less maintenance. In contrast intensive green roofs have deep soil layers, wide variety of plants are grown which add the weight and also they require high maintenance.
Since extensive green roofs have became subjects in scientific research, additional benefits began to gain importance. At present, ecological benefits such as reduced energy consumption for stormwater retention, heating and cooling, and heat island mitigation are the main reasons for the growing popularity of . Other benefits include habitat restoration, noise pollution reduction, filtration of acid rain and air pollutants, and the therapeutic effects found from being in the presence of nature.
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