A vegetated roof, also known as a green roof, is a roof that is partially or completely covered with vegetation and a growing medium, such as soil or compost. A vegetated roof can help reduce the heat island effect and manage rainwater runoff by providing the following benefits12:
It reduces the surface temperature of the roof by reflecting solar radiation and cooling the air through evapotranspiration, which is the process of plants releasing water vapor from their leaves. This can lower the ambient temperature of the surrounding area and improve thermal comfort for occupants and pedestrians.
It reduces the amount and speed of stormwater runoff by retaining and filtering rainwater in the vegetation and growing medium. This can prevent flooding, erosion, and pollution of downstream water bodies, as well as reduce the demand for potable water for irrigation or other purposes.
It enhances the biodiversity and habitat of the urban environment by providing a space for plants, animals, insects, and microorganisms to thrive. This can improve the ecological health and resilience of the ecosystem and provide aesthetic and recreational benefits for humans.
Other strategies that can contribute to reducing the heat island effect and managing rainwater runoff are:
White cement roof pavers: These are tiles made of concrete that have a high solar reflectance index (SRI), which measures how well a surface reflects solar radiation. White cement roof pavers can help reduce the surface temperature of the roof by reflecting more solar radiation than darker or less reflective materials. However, they do not provide any benefits for stormwater management, as they are impervious surfaces that do not retain or filter rainwater34.
A rainwater collection system: This is a system that captures and stores rainwater from roofs or other surfaces for reuse. A rainwater collection system can help reduce stormwater runoff by diverting rainwater from landfills or incinerators to other destinations, such as irrigation, toilet flushing, or cooling. However, it does not provide any benefits for reducing the heat island effect, as it does not affect the surface temperature of the roof or the surrounding air5 .
Shading structures that include photovoltaic panels: These are structures that provide shade for roofs or other surfaces by blocking direct sunlight. Shading structures that include photovoltaic panels can help reduce the heat island effect by lowering the surface temperature of the roof or the shaded area. They can also help generate renewable energy from solar power, which can reduce greenhouse gas emissions and energy costs. However, they do not provide any benefits for stormwater management, as they do not retain or filter rainwater .
