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As times goes on, more and more countries are urbanizing and this becomes a worldwide phenomenon. Cities are growing bigger in developed countries, and especially for developing countries with a huge number of population.
Trees and Animals are disappearing from our lives because of our violation to the environment. In order to replace the losing green environment, somebody come up an idea to plant vegetations on top of the buildings . This environmental technology is called the Green Roof.
The Green Roof is an environmental technology first founded in Germany in 1960s, and spread to other countries later. It covers the roof of a building with vegetation planted over a water-proof membrane with a design includes, as a minimum, a root repellent system, a drainage system, a filtering layer, a growing medium and plants. The picture shows below layers of a typical green roof.
There are 2 types of Green roofs – intensive and extensive. Intensive green roofs can support a variety of plants and growth but are more labour-intensive. They are more park-like areas which may also be used as recreation space.
The extensive green roofs, in contrast, require less maintenance (about once a year) and are designed to be self-sustainable.
There are lots of benefits to have a green roof. It serves several purposes for a building, such as absorbing rainwater during peak rates in storm, lengthen the roof life 2 to 3 times potentially and negate acid rain effect. It also acts as an insulator of heat so that the demand of winter heat decreased. A new habitat is made for wildlife while reducing the amount of CO2 and toxin in the atmosphere. As a result, there is a reduction in city “heat island” effect and low the urban temperature, therefore reduces summer air conditioning costs.
The main disadvantage of green roof is its high initial cost. ($8 per square foot is a minimum amount which includes materials, work costs and installation whereas values around $12 to $24 per square foot are the most common, and may even cost more for the traditional built-up roofs) Some green roofs have ongoing maintenance cost and thus enterprises may not want to put it in practice. Nowadays, there’s about 10% have been “greened” in Germany. (wikipedia) Besides Europe, green roofs are very popular in countries like United States, Canada, and Australia etc.
In Toronto, there’s a Eco-Roof incentive Program promoted by the City of Toronto to fund the green roof projects for industrial, commercial and institutional buildings. For more information, click the link below: http://www.toronto.ca/livegreen/greenbusiness_greenroofs_eco-roof.htm