The city of Rotterdam has turned more than 100 acres of rooftop green over the past decade. A green roof has a top layer of soil and vegetation that captures rain and reduces the amount of water that flows onto streets and stormwater systems. It may also have additional layers for waterproofing, root aeration and irrigation.
BENEFITS OF A GREEN ROOF
REDUCES STORMWATER RUNOFF: By holding rainwater like a sponge, green roofs ease street flooding and pressure on aging and increasingly overwhelmed stormwater systems. Retaining water allows excess moisture to evaporate or slowly drain out via gutters.
This orchard and community garden is actually on the roof of an old train station in Rotterdam, the Netherlands.
COOLS URBAN AREAS: Green roofs provide shade, remove heat from the air, and reduce indoor and outdoor temperatures. They moderate urban “heat island” effects by adding pervious, moist surfaces in areas dominated by streets, parking lots, conventional roofs and other hard, dry surfaces. Green roof temperatures are typically 30–40°F lower than those of conventional roofs. They can reduce the surrounding area’s ambient temperatures by 5°F.
REDUCES ENERGY USE: By reducing removing heat from the air and acting as insulators for buildings, green roofs can cut energy use by 7 percent in summer and 3 percent in winter.
CREATES HABITAT: Green roofs offer an oasis for plants, insects and birds in urban areas where natural spaces are limited.
PRODUCES FOOD: From vegetable gardens and fruit trees to chicken coops and bee hives, green roofs can accommodate a variety of food-growing enterprises.
INCREASES ROOF LIFESPAN: A green roof can cut down on roof maintenance and replacement costs by decreasing the hard inner roof’s exposure to storms, temperature fluctuations and sun damage.
A rainbow forms as rain falls near a rooftop garden in Rotterdam, the Netherlands.
