A green roof is a layer of vegetation planted over a waterproofing system that is installed on top of a flat or slightly–sloped roof. Green roofs are also known as vegetative or eco–roofs. They fall into three main categories—extensiveintensive, and semi–intensive. Although there are no precise definitions of them, an extensive green roof has a shallow growing medium—usually less than six inches—with a modest roof load, limited plant diversity, minimal watering requirements, and is often not accessible. Intensive green roofs have more soil and a deeper growing medium—sometimes several feet—that can support a more diverse plant selection, including small trees. Thus, they have more substantial structural loads and need more frequent maintenance and watering. They are usually accessible. Semi–intensive green roofs include features of both types. The appropriate depth of any green roof depends on the roof structure, the plants chosen, annual rainfall, and stormwater performance requirements.

Better roof durability

Green flora or vegetation is an additional layer on the flat roof that acts as a shield for roofing material. A green roof installation will protect the roof from UV rays, extreme temperature fluctuations, wind, rainwater and environmental pollution – thus prolonging its lifespan naturally. By installing a green cover over your flat roof, you are not just conserving the environment but protecting it from natural elements, too. The need for re-roofing will be less frequent, which means less cost over time.

Improved air quality

Leading cities of Pakistan have been becoming a concrete jungle and mostly lack of vegetation, plants and flora layers. It leads to an increasing level of pollution, and smog in all urban areas, which also increases carbon dioxide and other toxic pollutants. A green roof makes the most of unused space but help improve air quality because plants absorb carbon dioxide and other pollutants and emit oxygen. Green roofs help improve the environment and by installing one, you contribute to air purification.

Some green roofs are installed in one large integrated section, while modular green roofs use small portable planting beds placed together to create a larger green roof. The modular units are often plastic or metal trays filled with growing medium. Modular green roofs can be installed incrementally and are easily removed for maintenance and inspection of the roof layers underneath. Additionally, the modular sections can often be cultivated in a greenhouse and be ‘ready to plant’ on the green roof. Since the plants are already established, there are fewer issues with replacement plants that do not take root or thrive. One drawback however, is that moisture cannot flow between units, increasing the impacts of wet and dry spells on the plants.