Germany: state where green roofs are becoming part of architectural traditions
A green roof, or rooftop garden, is a vegetative layer grown on a rooftop. A green roof system is an extension of the existing roof which involves a high quality water proofing and root repellant system, a drainage system, filter cloth, a lightweight growing medium and plants. Green roofs can be installed on a wide range of buildings, from industrial facilities to private residences. They can be as simple as a 2-inch covering of hardy groundcover or as a complex as a fully accessible park complete with trees.
Today, in Europe about 10,000,000m² of new green roofs are being constructed each year. Germany is the country with the most green roofs in the world and it is the country with the most advanced knowledge in modern green roof technology. Sod roofs are frequently found on traditional farmhouses and farm buildings in Iceland. Switzerland has one of Europe's oldest green roofs, created in 1914 at the Moos lake water-treatment plant, Wollishofen, Zürich. Its filter tanks have 30,000 square metres of flat concrete roofs. To keep the interior cool and prevent bacterial growth in the filtration beds, a drainage layer of gravel and a 15-cm layer of soil was spread over the roofs, which had been waterproofed with asphalt. Through 2005, there were approximately 200 greenroof projects in Switzerland, totally about 10,000,000 - 15,000,000 m2. The cities of Basel, Zürich, and Luzern, for example now require that every new flat roof be planted per building code. As of the end of 2005, approximately 20% of the flat roofs are green roofs within Basel in the city of Basel in a year there will be around 80. This equals about 80 city projects totaling 480,000 m2, with the outlying countryside projects also around 80, estimated at 500,000 m2. In the United Kingdom, intensive green roofs are sometimes used in built-up city areas where residents and workers often do not have access to gardens or local parks. Extensive green roofs are sometimes used to blend buildings into rural surroundings.
The benefits of green roofs include:
- Reduced energy use: Green roofs absorb heat and act as insulators for buildings, reducing energy needed to provide cooling and heating.
- Reduced air pollution and greenhouse gas emissions. By lowering air conditioning demand, green roofs can decrease the production of associated air pollution and greenhouse gas emissions. Vegetation can also remove air pollutants and greenhouse gas emissions through dry deposition and carbon sequestration and storage
- Improved human health and comfort: Green roofs, by reducing heat transfer through the building roof, can improve indoor comfort and lower heat stress associated with heat waves.
- Enhanced storm water management and water quality: Green roofs can reduce and slow storm water runoff in the urban environment; they also filter pollutants from rainfall.
- Improved quality of life: Green roofs can provide aesthetic value and habitat for many species.
- Increased agricultural space
- Protection from ultraviolet rays: using reflective properties, green roof protects structure from ultraviolet rays and harmful electromagnetic radiation
- Reduced noise level: green landscape creates a good sound isolation, reducing the level of noise in the room up to 40 decibels.
Green roofs are one way to help mitigate the effects of climate change arising from the built environment, and are increasingly being seen as an important part of making cities less damaging.