Green roof of a building is described as roof covered with vegetation partially or completely on growing medium soil etc. Green roof vegetation is planted over water proofing material which is laid on the top of RCC slab to protect roof from dampness or leakage. Additional layers also include a root barrier, drainage and irrigation systems. Green roofs are made by placing layers of water proofing treatment deliberately over the roof to support growing medium and vegetation is relatively new phenomenon.
Go green living-better for health, better for nature
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In some cases containers i.e. pots are placed with green plants on the roof but this is not really a green roof. Painting merely by green color on the top of roof does not refer to green roof. Sometimes the roof having green technology is termed as ‘green roof’ such as water pool with green water, solar panels. Green roof has great effect such as it keeps temperature down particularly in urban areas where building proportion is more greening of the roof which has high impact for maintaining good environment. Green roof improves environment specially city’s, mitigate and storm water problem.
Green roof construction takes 30 to 40 days’ time for development. It includes vegetations, growing medium, drainage; irrigation system, water-proof installation and roof access are installed one by one on the top of roof slab. Depending on the size of green roof and types of plants, vegetations may need one or two growing seasons to be fully grown. The maintenance in built-up system requires regular watering, weeding, cultivation for survival of green roof.
According to cutting-edge research, green roof are divided into four categories as mentioned belows:
Green Roof Modular System
• This system is simple and easy to install.
• In modular system the depth of soil ranges from 3 cm to 15 cm.
• Green roof and maintenance process is very easy.
• This system is light in weight and has 6 to 8 Kg. weight per square feet.
• Growing medium usually contains sand, peat, gravel, organic matter, crushed bricks and some soil.
• It can be installed at any time throughout the year as vegetation is available pre- planted.
• Modular system has overall success in green roof because survival rates of vegetation are higher.
Green Urban Nature- Demand of time
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Green Roof Built In Place System
• This system of green roofing is expensive and even more complicated.
• This type of roofing is typically used.
• This type of roofing needs accurate design planning and is entirely finished before construction begins because green roof installation can not be changed easily.
• Built up in place system green roofing has typically loading ranging from 16-40 Kg. per square feet.
• This type of roofing system is heavier and requires more structural supports.
• Its growing medium is based on soil.
• In this type of green roofing system need more attention in selection of plants and used for public accessability.
Extensive green roof system
Extensive green roof system is designed for their aesthetic and environmental benefits, which is not typically designed for walking on. This type of green roofing systems is planned with low growing plants such as mosses and succulents. This roof system is low in maintenance cost because it is not designed to be on regular basis.
In extensive green roofing
The in extensive green roofing is comparable with roof garden and this is designed to access and therefore to be walked on larger shrubs and trees planted in this system. These require frequent maintenance. Extensive green roof system is typically used by local authorities or by public access organization which are opening their green roofs as a green space for people to visit.
Advantages of Green Roof System
• Green roof keeps temperature down which saves the cost of insulation.
• This roofing system reduces energy cost for maintenance of temperature of building.
• At rainy time, vegetation and plants of green roof observe water and reduce load on storm water system.
• Green roofing also create good environment in surrounding of the building.
• In flat green roofing, the space is used for recreation and meetings etc.
• Also the green roofing system presents economic and environmental benefits in metropolitan cities.
• In case of large building one can get flowers, vegetables etc. from green roofing systems.
Disadvantages of Green Roof
• The weight of soil and vegetation is born by roof slab. For this increased load, more strength of structure of the building is required.
• The maintenance of roof is costly after installation of green roofing system.
• The cost of water proofing system is increased to save the roof from constant watering and root damaging effect by green roofing system.