A green roof is a vegetated surface on a building roof or other architectural element, which provides ecological value, enhances building performance, and reduces stormwater runoff. Green roofs can be intensive (greater depth of planting medium that sustains a larger variety species of plants) or extensive (lower depth of planting that sustains smaller plants such as mosses, sedums, succulents, herbs and certain grasses).
- Compatibility with new or retrofitted rooftops
- Ideally, the rooftop should be relatively flat, with a 30 degree pitch
- The roof needs to be able to hold an increased load due to the added weight
- Requires a legal access point to the roof
- Watering may be required during initial installation stage and growth of vegetation
- Amount of regular watering required will depend on the type of vegetation and installation techniques used
- Inspecting vegetation-free zones, which are usually at perimeter to protect sensitive points, such as roof drains
- Removing litter, sticks, leaves, and other debris, and controlling of weeds as needed
- Checking of moisture level and irrigation system, especially during dry periods
- May require cutting and pruning in the fall
- Installation costs range from $64 to $226 / m² depending on building materials, complexity of design, and local availability of materials. This does not include the base roof cost.
- Annual maintenance is estimated to range from $2.7 to $44/ m²
- Site inspections should take place approximately five times a year and a maintenance company would likely charge $250 per site visit
- The lifespan of a green roof ranges from 10 to 30 years, which is similar to a conventional roof design. After this time, significant work may be required.
(Costs source: An Economic Analysis of Green Roofs by Sustainable Technologies)
- An Economic Analysis of Green Roofs: Sustainable Technologies Evaluation Program
- Green Roof Fact Sheet: Sustainable Technologies Evaluation Program
- Green Roof Policy Brochure: Sustainable Technologies Evaluation Program
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