Component: Green roofs

Description

Green roofs comprise a multi-layered system that covers the roof of a building or podium structure with vegetation cover/landscaping. The roof is likely to consist of an impermeable layer, a susbstrate or growing medium and a drainage layer (although not all green roofs require a drainage layer).

 

Green roofs are designed to intercept and retain precipitation, reducing the volume of runoff and attenuating peak flows.

 

Advantages and disadvantages

Advantages

Mimic predevelopment state of hydraulics and hydrology Good removal capability of atmospherically deposited urban pollutants Can be applied in high density developments Can be retrofitted (reliant on site specifics) Ecological, aesthetic and amenity benefits No additional land take Improve air quality Help manage urban heat island impacts Insulates buildings against temperature extremes Reduces the expansion and contraction of roof membranes Sound absorption

Disadvantages

Cost (compared to conventional roof) Not appropriate for steep roofs Opportunities for retrofitting may be limited by roof structure (strength, pitch etc) Maintenance of roof vegetation Any subsequent damage to waterproof membrane likely to be more critical since water is encouraged to remain on the roof

 

 

 

 

 

 

 

 

 

 

 

Where component can be used?

Residential:  Yes
Commercial/industrial:  Yes
High density:  Yes
Retrofit:  Yes
Contaminated sites:  Yes
Sites above vulnerable groundwater: Yes

 

Performance

Peak flow reduction:  Medium
Volume reduction:  Medium
Water quality treatment: Good
Amenity potential:  Good
Ecology potential:  Good

 

Maintainence

• Irrigation is needed during establishment of vegetation for some roofs

• Inspection for bare patches and replacement of plants will be required on a regular basis

• Litter removal may be required (depending on setting and use)

 

Read more on:

• Source control

• Green roofs

• Rainwater harvesting

• Pervious surfaces

• Other permeable surfaces