A green roof is a roof covered wholly or partly with living vegetation, built up from a waterproof layer, drainage, substrate and planting. It combines the protection of an ordinary roof with the benefits of greenery on the building.
Types of green roof
- Extensive green roof — a thin, light layer of sedum, mosses and herbs; low maintenance and suitable for many existing roofs
- Intensive green roof — a thicker build-up with grass, plants and even shrubs or trees; heavier, more maintenance and often accessible as a roof garden
- Blue-green (retention) roof — a green roof also designed to buffer and slowly release rainwater
Advantages
A green roof offers several benefits:
- Water storage — it buffers rainwater and relieves the sewer during heavy downpours
- Insulation — it dampens temperature swings and keeps heat in
- Longer life — the planting protects the roofing membrane from UV and heat
- Biodiversity — it provides habitat for insects and birds
- Cooling — it counters urban heating (heat stress)
Points to watch
Key requirements are good waterproofing, adequate load-bearing capacity of the structure and a reliable root-resistant layer. The extra load from substrate and water must be allowed for in the roof structure.
Related Terms
- Roofing
- Retention roof
- Water storage
- Climate adaptive
- Green facade
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