Green roofs are becoming increasingly popular in urban areas. These roofs offer several benefits for the urban ecosystem. A green roof is simply beautiful compared to the alternative black tar roof.
Urban development has altered how water travels through the landscape. As impervious surfaces increase, water is forced to evaporate or run off. In the heart of a city where there is 75 percent to 100 percent impervious surface most of the rainfall becomes runoff and infiltration is less than one-third of what it was prior to development. A green roof can reduce, delay and cool stormwater runoff.
A green roof can reduce the urban heat island effect. As plants transpire, they create a cooling effect, lowering the temperature on the roof. The building is cooler, reducing the need for air conditioning and therefore reducing building energy costs.
A green roof can increase the longevity of the roof by protecting it from ultraviolet rays.
A green roof can be a sound barrier for buildings located near an airport, a highway or industry.
A roof can be used to create a garden where ground space is not available. This rooftop space can be used to produce food in an urban food desert and provide needed green space in a concrete jungle for humans, birds and pollinators.
The type of plants used depends on the type of green roof. There are two types, extensive and intensive. An extensive green roof has a soil depth of 1 to 5 inches and utilizes drought-tolerant plants such as sedums and short grasses.
An extensive green roof is typically used on a rooftop that is not accessible by humans. The roof needs to be constructed to withstand the additional 15 to 50 pounds per square foot of weight from the soil.