Green roofs are one of the most effective ways to reduce the ambient air temperature in urban areas. During summer the temperatures in cities are approximately 5-7°C higher than in the countryside due to buildings and roads heat absorption and the temperature on the traditional roof can be up to 40°C higher compared to the green roof.
A major advantage of green roofs is the reduction of storm water runoff, which leads to a decrease of the burden on sewer systems by 50-90% in summer, depending on the green roof design and local climate. Green roofs have influence on cost reduction due to low or no need for raincatching cisterns and similar equipment which is usually used for storm water management. Rainwater retention capability helps to limit accidents caused by heavy rainfalls.
Through natural bio-filtration, green roofs prevent contaminants and toxins from reaching streams and waterways.
Green roofs help to reduce the amount of CO2 in the air, which is considered one of the most important causes of global warming. 1m2 of a green roof can absorb 5kg of CO2 yearly. Additionally, due to reduced energy consumption there is a further impact on carbon dioxide reduction by 3.2kg yearly. As a perspective, 1m2 of green roof can absorb the same quantity of CO2 as a regular car would emit during a 80km drive.
The plants on green roofs can also capture airborne particles such as smog, heavy metals and volatile organic compounds from the local atmosphere which has a positive effect on air quality and health of inhabitants. Researchers estimate that 1m2 of a green roof can help to absorb 0.2kg of airborne particles from the air every year.
As urbanisation increases, ensuring biodiversity is one of the key requirements for local councils. Green roofs can provide a habitat for various species and restore the ecological cycle disrupted by urban infrastructure.