What is Green Roof
Green roof refers to a system of roofing that uses plant life for roof covering instead of traditional covering materials. The system of green roofing dates back to the 1960’s but only in recent years it has became a popular alternative to the traditional roofing due to its environmental benefits and savings for heating and cooling. The plants that cover the roof provide an excellent insulation to the building reducing energy consumption significantly but they also act as a natural filter for rainwater which means that they significantly reduce the amount of rain drainage. The plants absorb over 50% of rainwater which would otherwise run into sewage system. The water that is absorbed by the plants on the rooftop then evaporates back into the air. But the benefits of green roof technology do not end in reduction of rainwater.
Green roofing has become increasingly popular in cities because it creates additional green spaces that bring some nature in the concrete and steel jungle. Green roofs in larger buildings and often mimic parks and include rich vegetation that does not only provide an additional green space but also attracts wildlife including butterflies, honeybees and other insects as well as birds that can be otherwise rarely seen in urban areas. In addition, green roofs are visually appealing and create an attractive contrast to concrete and steel, while many people take advantage of possibility to grow their own fruits and vegetables as well as flowers on rooftops. Some even have a nice set of childrens garden furniture and a garden parasol to get the best of the sunshine.
As already mentioned earlier, green roof is covered with plants, most often vegetation that is resistant to weather effects and requires little or no irrigation. Native, hardy, pest- and disease-resistant, and fireproof plants that grow fast and are not invasive are ideal for green roofs. In addition to collecting rainwater, plants on rooftops also absorb the heat which keeps the building warmer during cold winter months, while the growing medium helps keep building cooler during hot summer months. Green roofs have been shown to reduce the costs for cooling and heating for as much as 50 percent offering major financial benefits to building owners. Another major advantage is green roofs over conventional roofing is absorption of air pollutants including carbon dioxide by the plants which helps lower the temperatures in the urban area and reduce the heat island effect.
Green roofs are always created in several layers which besides plants include a growing medium, filter cloth, drainage, insulation as well as waterproof membrane. The construction of a green rooftop as well as selection of plants for roof covering depends on several factors including the size of the building and the type of the roof. Both flat and slopped roofs are appropriate for green roofing but creation of park-like roof systems remains limited to larger buildings as accommodation of large plants and trees is too heavy for houses and medium-sized buildings.
According to plant selection, there are three main green roof types called intensive, semi-intensive and extensive. Intensive green roofs refer to rooftops that accommodate large plants including trees, full lawn, etc. This type of green roofing requires a significant depth of soil as well as lot of maintenance, similar to maintaining a park or large garden. Semi-intensive green roof involves roof covering with plants of moderate size and requires less maintenance. Extensive green roof is the most convenient of all types of green roof systems and involves roof covering with a thin layer of growing medium and vegetation that requires minimal care and maintenance.
Green roof technology is the most environmentally friendly roofing system and has one disadvantage only. The initial costs for green roof are much higher than for traditional roofing due to higher costs for construction works. Despite that it is more cost-efficient than the cheapest roofing systems because green roof technology provides significant savings for heating and cooling. According to some estimations, green roof lowers the costs for heating and cooling for over 50%. In addition, green roof systems are extremely durable. It can last as long as 50 years and requires virtually no repairs like many other roofing systems. Green roofs combined with other green technology such as solar thermal collectors and solar photovoltaic panels can further reduce the costs for heating and cooling as well as help combat the global warming.