Benefits of Green Roofs
Quality of Life
- Well-being is widely acknowledged to be enhanced by green spaces and interaction with nature.
Stormwater Management
- Green roofs can significantly reduce the water runoff volumes and also delay the time at which runoff occurs, resulting in decreased stress on sewer systems.
Reduction of Heat Island Effect
- Through the daily dew and evaporation cycle, green roofs are able to help to cool surrounding areas and reduce the heat island effect.
Air Quality
- Airborne particles and pollutants are filtered from the atmosphere by the substrates and vegetation on a green roof.
Energy Efficiency
- The greater insulation offered by green roofs can reduce the amount of energy needed to moderate the temperature of a building. Roofs are the site of the greatest heat loss in the winter and the hottest temperatures in the summer.
Noise Insulation
- The combination of soil, plants and trapped layers of air within green roof systems can act as a sound insulation barrier.
Biodiversity
- Green roofs create biodiversity, encouraging wildlife, such as birds, butterflies and insects, to remain within urban areas.
Green roofs are engineered systems that incorporate vegetation above traditional roofing. Over 90% of the roof at the Cowichan campus is covered by a green roof.
There are two types of green roofs:
- Extensive Green Roofs
- 3-6" of light weight growing medium.
- Low-maintenance ground-cover plants.
- Desert grasses and succulent plants (after one year, they do not require watering).
- Require annual spring weeding of tree seedlings & weeds - brought in by birds and wind.
- Intensive Green Roofs
- 8-12", or more, of growing medium.
- Fully landscaped roof top garden.
- Require regular maintenance.
- Diverse plants and trees can be planted.
- Can sustain walkways, benches and trees.
The layers of a green roof must, like any roof, accommodate drainage and protect the building from the elements with a waterproof membrane. But they also must create a growing area and potentially provide support, irrigation and root protection barriers while staying as light as possible.
Specific plant species are chosen based on their performance and suitability for roof conditions, and are mainly native/adaptive species. By varying this green roof with extensive and intensive planting, we are able to optimize the green roof benefits.
Over 90% of the roof at the Cowichan Campus is a green roof.