A garden roof incorporates the micro-ecosystem of a garden into the roofing structure of a building. A garden, complete with growing medium and water delivery system, is integrated into the roofing system to create an organic space that supports flowers, grasses, herbs and vegetables. Garden roofs benefit the environment and are particularly beneficial in the urban landscape.
Local Temperature Control
Concrete, steel and glass make up a large part of urban landscapes. These materials attract and retain heat and in the densely built cities, this creates what is known as the urban heat island effect. Temperatures are higher in the city than in the outlying areas.
Clusters of garden roofs atop city buildings reduce those temperatures. Through the process of transpiration, the plants cool down the surrounding air. They absorb the heat, and release cooled air, thereby reducing localized temperatures.
Interior Temperature Control
Roof gardens also reduce the interior temperature of the buildings on which they reside. The plants and surrounding growing medium, such as soil, absorb heat and use it in the localized eco-system that is the garden. The building roof is no longer a heat-trapping receptacle that transfers heat into the interior. It is now a sunlight-processing garden that uses the heat to make plants grow.
Gardens provide food and shelter for local insects, birds and butterflies. Garden roofs, particularly urban garden roofs, not only provide these necessities, but also attract these life forms to an environment that would otherwise prove hostile.
Without local organic food and shelter, these environmentally beneficial creatures either seek out new habitats or die out. Cities displace wildlife, thereby disrupting local eco-systems. Roof gardens partially alleviate that displacement.
The density of cities, in terms of people, buildings and modes of transport, creates concentrated clouds of pollution. The employment of numerous methods is necessary to reduce localized pollution. Garden roofs are one of these methods.
Plants produce oxygen and remove carbon dioxide from the air. The elevation of garden roofs is advantageous in that clusters of these gardens within an urban environment can act as "scrubbers" to clean localized air. While garden roofs alone cannot remove all pollutants, their presence in large numbers would prove beneficial when taken in conjunction with other pollution reducing measures.
Garden roof technology is expensive, but owners of commercial buildings benefit from tax incentives as well as resale value from the installation of garden roofs. As the trend to go green becomes integrated into local building codes and tax incentives become more common, buildings already equipped with roof gardens prove salable in the market, attracting conscientious buyers willing to pay for environmentally friendly buildings.