Green Roofs Introduction
What are Green Roofs (1)
“A roof garden is an area of largely ornamental planting whose substrate is isolated from the natural strata”
•Hanging Gardens of BabylonHanginggardens
•Recent increased application
•Legal requirement in areas of Germany & Switzerland
- Utilisation of the fith facade (Roof)
- Helps with the problem of polluted air in urban locations
- Helps to reduce the visual and environmental impact of development in the countryside.
Green Roofs Intensive Roofs
- Intensive roofs are designed to accept all forms of human activity
- The equivalent to a normal recreational garden like the Canary Wharf Estate.
- They contain a deep growing medium which contains a full range of plants, trees, play areas.
- Intensive roofs can be referred to as Roof Gardens.
- Have public access
- Deep soil (>200mm)
- Mechanical irrigation
- 0 - 2percent slope of the roof
Intensive roofs have a diverse utilisation.
The considerations at the design stage are:
Plants and trees will need to be selected that are suitable to go on a roof
There needs to be further insulation installed in the roof so that it protects the building from leaking, also intensive roofs help insulate the building.
Depending on the type of plants used will depend on the medium of the green roof.
Static load bearing
The depth of the extra growing medium require extra loading requirements within the holding structure. In order to carry the extra weight.
The Structure will require a complex irrigation system for maintenance and will need regular maintenance.
This type of green roof is generally quite costly and require extra structural design to the building.
Green Roofs Extensive Roofs
This type of roof is
- plants growth is slow.
Extensive Roofs require little or no maintenance (Yearly for weeding)
- roof decks that are lightweight
- roofs that are Inaccessible to reach
- Roofs that are required to be landscaped to comply with planning consent (fit within Landscape)
- There is no public access to extensive roofs
- There is a thin soil/growing medium (<200mm)
- The growing conditions are harsh due to growing medium layer.
- there is little or no need for mechanical irrigation.
- Moss, herb and grass species.
- 0 - 30 percents slope of the roof.
Due to having a thin growing meduim
The roof will not require as much extra load bearing
this is because they have a low meduim and may not need maintence deping on plants used.
They are left to grow which allows them to be untouched.
Act as a thermal buffer to the roof
helps to retain heat in the building.
Key Considerations for Green Roofs
Improves the utilisation of land (more green)
Helps to cool the air (heat Island effect)
Controls of air humidity (plants can absorb carbon dioxide release oxygen and encourage wildlife)
Cost of construction & maintenance
Load bearing? (extra design to carry weight)
- Intensive 2+ tonnes per sq metre
- Extensive 650kg per sq metre
- Ordinary roof 100kg per sq metre
Key Considerations for Green Roofs
Helps retention of Rainwater
- likley hood of local flooding
- delays runn-off during times of heavy and prolonged precipitation.
Gives protection of weather proofing from ultra violet rays
Reduce the Reduction of Temperature extremes
- green roofs buffers roof membrane
- life of roof is increased
- thermal insulation can be increased by up to 10%
Protection from heat and noise (noise insulator)
Popularity of Green Roofs
Uk has an high interest but low take up,
10,000 km2 of green roofs constructed in the uk
3,500,000km2 of green roofs constructed in the Germany (money insentives)
1/5th commercial premises in Nottingham City have flat roofs
Popularity in Germany
New buildings must provide a replacement value or provide compensation.
this encourages inceresed flexiblity between sensible land use and encouraging development