These days, green roofs are being used as an oasis to the dense urban environment. The fast growth of urban settlements and the advancement of technology have widened the gap between human beings and nature. Green roofs are one of the pathways back to nature.
A green roof is a roof in which its outer surface is covered with vegetation. Green roofs often include a growing media which varies from a thin compost layer to a thick soil layer and a waterproofing membrane beneath the growing media. Green roofs can also have drainage and irrigation systems integrated into them. There are mainly three types of green roofs categorized according to the depth of the planting medium, the need for maintenance and accessibility. The three types of green roofs are
Extensive green roofs mostly tend to be self-sustaining and require minimum maintenance. Mostly, extensive green roofs are constructed with a very thin layer of soil. Most of the time, they are accessed only for maintenance purposes.
Intensive green roofs on the other hand, are able to grow shrubs, vegetables and even small trees. Unlike extensive green roofs, intensive green roofs need a reasonable depth of soil.
Green Roofs vs Roof garden
A roof garden is very different from a green roof, although the two terms are often and incorrectly used interchangeably. A roof garden is an area that is generally used for recreation, entertaining, and as an additional outdoor living space for the building’s resident(s). It may include planters, plants, dining and lounging furniture, outdoor structures such as pergolas and sheds, automated irrigation systems and lighting systems. A roof garden re-establishes the relationship between man and nature that can be lost in urban environments whereas a green roof is usually constructed to cover a large area in the most economical and efficient means possible with an emphasis towards improving the insulation and/or improve the overall energy efficiency of cooling and heating costs within a building.
In general, green roofs are very useful for the inhabitants of the building and the environment in many aspects. The roof, being directly exposed to the sun, is usually responsible for most of the heat gain in a building. Green roofs reduce heat gain by adding mass and thermal resistance value for the inner roof. It is believed that the collection of green roofs in the urban area can also reduce the city’s average temperatures during the hot season.
Green roofs can also filter out carbon dioxide and other pollutants from the surrounding air. Some studies in this regard have shown that this air filtering by green roofs helps lower rates of diseases such as asthma.