Green Roof And Roof Gardens

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Green roofs and roof gardens are terms that are often used interchangeably when referring to a roof that supports vegetation. Professionals, however, draw a distinction between the two types (147); roof gardens are installed for the access and enjoyment of people. They are also costly to build, require intensive maintenance and are heavy in weight due to the deep soil profiles. In contrast, green roofs are lightweight with thin soil profiles and minimal maintenance requirements. They are cheaper to construct as they are installed for environmental performance and visual improvement only. The origin of green roofs can be traced back to the vernacular architecture of various regions, while roof gardens have been documented as being built by the …show more content…
Known to exist for centuries, in form of Sod roofs in Scandinavia, vegetated roofs provided extra warmth and insulation in the cold, wet climate (152). However the susceptibility to leaking, extensive maintenance and frequent replacement, lead to eventual rejection of sod roofs in favor of new leak proof construction techniques.
Other vernacular examples have been recorded in the traditional houses of tropical regions of China and Japan. The summer rainfall was often damaging for the region, but increase in summer humidity levels supported the growth of vegetation on roofs. Plant roots helped in bonding and strengthening of the structure (153) and protected the thatch from washing away. Development of modern building materials reduced the number of traditional green roofs as new roof assemblies were cheaper, easy to construct and required less
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Such green roofs provide greenery on the building roof and help preserve biodiversity at that height by providing natural habitat for plants, birds and insects.
Extensive roofs have a narrower range of plant species limited to herbs, low growing grasses, mosses and drought tolerant succulents such as sedum (155). Substrate depths are relatively thin between 0.05 m (2”) to 0.15 m (6”) which are significantly lower than intensive roofs (156). Saturated weights for extensive green roof system are approximately in the range of 48.8 – 170.9 kg/m² (10-35 lb/sq ft). Extensive green roofs do not require regular input of resources like water, labor as required by an intensive roof and can be designed for steeper slopes (greater than 2:12) (155).
These systems can often be installed on existing buildings without additional structural costs and alterations, but an engineering analysis of the structure must be performed. Careful selection of plants and growth medium ensures the success of a green roof