Sustainability in architecture – green roofs
The use of precast planks as a design option for roofing over our semi-basement garage seems to most as being the one and only option. If the ‘perit’ proposes a reinforced concrete slab design, then he is only doing so to make him pay more money on the total construction costs. But how much of this is true? Is there really a cost factor between the use of precast planks and cast in-situ concrete?
So, where do green roofs come in play ? Green roofs in this sense help by providing a better internal living environment without the need of any additional resources that require further energy to perform. Benefits of green roofs also include:
- Improved air circulation around the building
- Increasing internal energy efficiency – cooling in summer, insulation in winter
- Filtering and cleaning toxins from both air and water
- Reducing carbon dioxide emissions, thus lowering the building carbon footprint
- Reducing urban temperatures and associated smog
- Insulating against sound and noise
- Preserving and enhancing biodiversity
- Providing aesthetic appeal and ‘green space’ recreational opportunities
Types of Green Roofs
Green roofs are generally categorized as either intensive or extensive, depending on the depth of planting medium and the amount of maintenance they need.
Intensive
Roof gardens which require a reasonable depth of soil to grow large plants or conventional lawns and are labour-intensive, require irrigation, feeding and other maintenance.
Typical use: Office buildings & Hotel Roofs
Typical medium depth for lawn: 15 to 35 cm
Example: Chicago City Hall
Extensive
Designed to be virtually self-sustaining and require only a minimum of maintenance, perhaps a once-yearly weeding or an application of slow-release fertiliser to boost growth. They can be established on a very thin layer of “soil” (most use specially formulated composts). Even a thin layer of rockwool laid directly onto a watertight roof can support a planting of Sedumspecies and mosses.
Typical use: Household roofs which are generally inaccessible to public
Typical medium depth for moss-sedum: 2 to 6 cm
Example: Glengarda Children’s Centre
