Roof gardens are often divided into two categories: extensive and intensive. Extensive roof gardens, which are more common and fewer complicated, are typically constructed to a depth of 6” and are frequently designed to satisfy performance goals. Intensive roof gardens, which may be relatively deep, commonly include large plants, trees, and elaborate gardens that need much maintenance. Key benefits of roof gardens include controlling storm water run-off, mitigating urban heat island effects, and reducing echo and transmission.
Working our high from rock bottom , a typical garden (extensive in our example), commonly includes these important layers (not including the substrate and insulation):
Waterproofing | Roof Membrane: this is often crucial to a garden . Approved waterproofing layers will vary by manufacturer.
Root Barrier: Should be composed of concrete or waterproofing membrane.
Drainage: Often includes plastic sheets, granular mineral layers, or fabric and artificial mats. Gravel or pumice is usually used on the brink of the gutters and scuppers to assist drainage.
Water Filter: Polyester or polypropylene cloth is employed . This layer filters water while keeping the highest layers together.
Growing Medium: the highest two layers are soil and vegetation. Selection varies counting on the specified outcome like run-off control, appearance, accessibility to the general public , and drought tolerance. For the soil, it's important to use a growing medium which will not foster weed or pathogen growth.
Vegetation: to make sure that your plants thrive, use plants that are found in your growing zone or a minimum of are hardy enough to face up to the weather . Also take into consideration the upkeep the plants would require .
Structural Considerations:
Green roofs are heavy, even extensive ones. If installing a garden on an existing structure, you'll got to have the building evaluated first. Consult a roof contractor who can tell you ways much your existing roof can hold and what extra structural support could also be required. the good Lakes WATER Institute of the University of Wisconsin Milwaukee in their green roof project spells call at detail the prices and weight considerations.
Extensive roof gardens have a soil depth of 1" to 6" and may weigh between 15 and 50 lbs per sq ft .
Intensive roof gardens have a soil depth of quite 6" and may weigh anywhere from 80 to 150 lbs per sq ft .
Green roofs are an enormous investment, especially financially. However, the advantages outweigh the value . Not only do green roofs help to combat urban heat island effect, they're energy-efficient and may be quite useful, particularly if they include vegetable gardens and fruit trees.
The benefits of green roofs include:
- Longer roof lifespan
- Improved sound insulation
- Reduced heating and cooling requirements
- Reduced and slowed storm-water runoff
- Capture of gaseous and particulate pollutants
- Alleviation of urban heat island effects
- Increased biodiversity.
Many of those benefits also apply to green walls.
There is also the potential for green roofs to supply carbon sequestration.
Types of Green Roofs
Extensive green roofs
Extensive green roofs have a shallow profile. they supply much of the environmental performance benefits of deeper, intensive green roofs but cannot support general pedestrian traffic . Their shallower profile means less substrate volume to store water and support root growth (although there's still enough to scale back and slow stormwater runoff), and this limits the variability of plant options to people who tolerate environmental stress, especially drought and desiccating winds.
Extensive green roof characteristics
- Shallow growing medium — typically but 200 mm
- Roof structure almost like conventional roof coverings
- Weight 60–200 kg/m2
- Vegetation generally limited to low, shallow-rooting and ground cover plants that are tolerant of drought, windage and temperature fluctuations
- Not suitable for general access
- Relatively economical
- Some thermal and acoustic insulation benefits
- Relatively easy to retrofit on existing roofs
- Low maintenance
Extensive green roofs, often situated in urban areas, require low maintenance vegetation tolerant of warmth , cold, drought and wind. Although there's limited experience in Australia of such roofs, it's likely that a lot of native plants from coastal and arid inland regions are suited to use in such harsh and demanding environments.
Intensive green roofs
Intensive green roof profiles can range from 200 mm to over 1 m deep. This increases the quantity of growing media available for root development and water-holding capacity and greatly extends the variability of plants which will be grown. the extra weight demands a stronger physical roof structure than extensive green roofs but allows for pedestrian traffic . Intensive green roof gardens are often as richly planted and landscaped as ground level gardens. They require an equivalent level of maintenance as conventional gardens.
Intensive green roof characteristics
- Deep growing medium — 200 mm or greater
- Requires stronger roof structure
- Weight 180–500 kg/m2 or more
- Wide range of plantings possible, from ground cover to trees
- Suitable for access and use as garden — wide scope for design and multiple uses
- Relatively expensive thanks to structural requirements
- Substantial thermal and acoustic insulation benefits
- Difficult to retrofit on existing buildings
- Regular maintenance required
In between these types there are semi-extensive (extensive with areas of deeper soil) and semi-intensive roofs (intensive with areas of shallower soil).
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