Green roof ~ green with reference to the general appearance of
plant growths and for being environmentally acceptable. Part of
the measures for constructing sustainable and ecologically friendly
buildings.
Categories ~
- Extensive ~ a relatively shallow soil base (typically 50 mm) and
lightweight construction. Maximum roof pitch is 40^0 and slopes
greater than 20^0 will require a system of baffles to prevent the
soil moving. Plant life is limited by the shallow soil base to
grasses, mosses, herbs and sedum (succulents, generally with
fleshy leaves producing pink or white flowers). - Intensive ~ otherwise known as a roof garden. This category
has a deeper soil base (typically 400 mm) that will provide for
landscaping features, small ponds, occasional shrubs and small
trees. A substantial building structure is required for support
and it is only feasible to use a flat roof.
Advantages ~
- Absorbs and controls water run-off.
- Integral thermal insulation.
- Integral sound insulation.
- Absorbs air pollutants, dust and CO 2.
- Passive heat storage potential.
Disadvantages ~
- Weight.
- Maintenance.
Construction ~ the following build-up will be necessary to fulfil the
objectives and to create stability:
- Vapour control layer above the roof structure.
- Rigid slab insulation.
- Root resilient waterproof under-layer.
- Drainage layer.
- Filter.
- Growing medium (soil).
- Vegetation (grass, etc.)
Examples of both extensive and intensive green roof construction
are shown on the next page.
Green Roofs