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.