What is an Eco-Roof?

An eco-roof consists of a water proofing membrane, a growing medium, like soil, and vegetation overlying a traditional roof.

There are two types of eco-roofs, extensive and intensive. Extensive roofs are relatively inexpensive to install and are mainly used for environmental benefits. Extensive roofs have a thin layer of soil and plants that can survive in harsh weather conditions such as succulents. Intensive roofs allow for a greater variety and size of plants, and are usually more expensive to install and maintain.

An eco-roof  here in downtown Portland
Benefits from eco-roofs include: improved water quality due to reduced storm water runoff, increased habitat promoting biodiversity, improved air quality, urban heat island reduction, and reduced energy consumption.

Storm water runoff: excess storm water runoff can cause a number of problems, like damaging water quality by sweeping debris into local bodies of water. In older cities storm drains are typically combines with sanitary sewers, large volumes of storm water can cause combined sewer overflow and lead to untreated sewage being discharged into rivers and lakes. Eco- roofs can reduce the frequency of combined sewer overflows and can reduce roof runoff by up to 65%.

Air quality: The vegetation on these eco-roofs can remove air pollutants like carbon dioxide and carbon monoxide. The eco-roof’s effectiveness at removing pollutants depends on the types of plants gown.

Urban heat islands: Urban heat islands are highly built up areas that are usually warmer than surrounding suburban areas due to the absorption of solar radiation by building and non plant surfaces, such as side walks and roads. Eco- roofs absorb less sunlight than traditional roofs, and cool the air around them.

Reduced Energy Consumption:Eco-roofs can help reduce energy consumption through the process of evapotranpiration. Evapotranpiration is the process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration, the process where plants absorb water through the roots and then give off water vapor through the pores in their leaves.