Green roofs are an innovative and environmentally friendly solution for the optimal use of roofs, creating vibrant, functional green spaces
They are made up of various special layer systems, including drainage systems, protective layers with various functions and special substrates that allow the optimal growth of vegetation on the roof, creating a favorable natural environment.
Depending on the requirements and load-bearing capacity of the building, green roofs can be designed to allow pedestrian and vehicular traffic, providing a range of recreational and practical functions similar to those of green areas at ground level. Depending on the characteristics and location of the building, green roofs can be built on any type of roof, regardless of slope or pitch angle. For low slope roofs, no special design is required, but for roofs with a slope greater than 15o, a special anti-erosion system must be included in the structure of the layers to provide secure support for vegetation and substrate, and allow efficient drainage.
The main component of green roofs is the vegetation, which can consist of many plant species. Depending on individual preferences and the load-bearing capacity of the building, vegetation can include succulents (sedums), grasses, perennials, wild flowers or even complex and varied green areas with shrubs and trees. The choice of plant species used in the green roof structure also determines the structure of the further layers, which must be adapted to the needs of the plants. Vegetation is planted in a special substrate, which is the next layer of the structure, that provides a suitable environment for the development of healthy vegetation and is adapted to the load-bearing capacity of the roof, with a low organic matter content.
Underneath the substrate, a layer of geotextile filter fabric is usually installed to prevent fine particles, granules and impurities from the substrate from entering the drainage system. The drainage layer plays an essential role in the efficient functioning of the green roof system, ensuring that rainwater is drained away and stored in special compartments so that it can be absorbed by the plants during dry periods. A protective geotextile is placed under the drainage layer to protect the waterproofing against possible mechanical impacts and damage, both during work and after installation. If the waterproofing is not resistant to root penetration, it is recommended to install a root barrier foil to prevent damage to the building’s waterproofing by invasive plant roots.
Green roofs have deep roots in history, with the first written records dating back thousands of years. These include the famous Semiramis Hanging Gardens, considered one of the Seven Wonders of the World. Although there is no tangible archaeological evidence to confirm their existence, written memories of these gardens continue to inspire and captivate humanity until present days. These gardens are said to have been built in the middle of the desert and were a real oasis of greenery for humans. They were suspended on stone terraces, reaching up to 75 metres high, and benefited from complex drainage systems, water wheels, canals and irrigation systems, which ensured dense vegetation even in extreme desert weather conditions. Vegetation consisted of rare plant species brought from exotic places. Hanging gardens have remained an impressive symbol of beauty and harmony.
Another fascinating historical monument is the Scandinavian green roof, known as the ‘torvtak’, which is frequently used because of its thermal insulation benefits. These roofs were made from moss, grass, turf or natural soil and date back to Viking times. They were extremely resistant to harsh weather conditions and adapted to the local climate. Their main role was to provide thermal insulation and efficient drainage of downpours, while providing an aesthetically pleasing, harmonious and natural appearance in the built environment.
Many types of green roofs were also found in the Middle East, where they were mainly used to provide effective thermal insulation and to cool buildings in hot, dry climates.
Since the 20th century, as humanity has become more concerned about protecting the environment and seeking solutions for a sustainable future, green roofs have gained increasing attention and become popular worldwide. Much research and development has been undertaken to create modern green roofs, and Germany has played a key role in this process. Thanks to extensive research in the 1960s and 1970s, many innovations and improvements were made in the structure and materials used for modern green roofs.
Today, as the need for effective solutions to environmental problems grows, green roofs are gaining increasing popularity due to the many environmental and economic advantages they offer.
Depending on the type and complexity of vegetation and structure, as well as maintenance requirements, several types of green roofs can be distinguished. Each type has its own characteristics and should be selected according to individual needs and the characteristics and location of the building.
Extensive green roof
This type of green roof is the simplest and lightest in structure and weight. It usually consists of succulent plants (Sedum), mosses or grasses. Due to the characteristics of the plants, it requires a thin layer of substrate and occasional maintenance. Although it is a structurally simple system, it can provide a captivating and aesthetically pleasing view due to the brightly coloured vegetation.
Semi-intensive green roof
As the name suggests, this type falls between extensive and intensive green roofs in terms of structure and maintenance requirements. In this type of green roof vegetation can consist of a wider variety of grasses, perennials or even small shrubs. A common example is vegetation imitating meadows with numerous species of wild flowers. The semi-intensive system requires a thicker layer of substrate and more rigorous maintenance than the extensive system. For example, regular mowing and watering may be required to maintain an aesthetic appearance throughout the year.
Intensive green roof
This is the most complex type of structure, allowing the construction of complete green recreational areas, including trees, shrubs and, in addition to the vegetation mentioned above. More diverse and rich vegetation requires a thicker layer of substrate to ensure safe and healthy growth. Due to its specific characteristics, this type requires regular and frequent maintenance, similar to green areas at ground level (watering, irrigation systems, pruning, grass cutting, etc.).
Biodiverse green roof
This is a special type of green roof dedicated to promote biodiversity, including specific native plants that can provide habitat for a wide variety of small animals such as insects and birds. In addition to vegetation, it can also include areas with a variety of materials and textures that contribute to biodiversity, such as gravel, sand, soil, hills and small wetlands. In addition, various natural elements can be used to provide shelter (stones, tree branches, etc.). By combining the biodiverse green roof with Blueroof and/or solar system, the environmental benefits can be maximised.
Green roofs offer a series of environmental, economic and aesthetic benefits, including reduction of negative impact of urban development, reducing pollution, promoting biodiversity and providing a habitat for different animal species.
Also, thanks to the special drainage system and the absorbing capacity of plants, green roofs are able to efficiently drain large amounts of rainwater, facilitating the functioning of often overloaded urban drainage systems. In addition, plants help purify stormwater by retaining harmful substances.
Another important aspect of green roofs is reducing the urban heat island effect, an increasingly common problem in dense urban environments. Green surfaces, unlike concrete and asphalt elements, do not overheat, but form humid and shaded areas, helping to reduce temperatures by evaporating plants. On the other hand, green roofs have a thermal insulating effect on the building, helping to reduce the energy needed to cool and heat the building.
In addition to the many economic and environmental benefits, green roofs also have a positive impact on human well-being, bringing nature closer to people and providing a relaxing atmosphere. Vibrant green surfaces add an aesthetic, harmonious and natural look to an often grey and bland urban environment.