Role of Green Roofs for Zero Energy Buildings
Touch of green roofs into the human lives and contributing visual richness by planting were encountered in Hanging Gardens of Babylon founded in B.C. 700’s for the first time. There were also planted areas in the terrace of important buildings and public buildings in Roman Empire in B.C. 1000’s as indicators of richness and luxury. Grass planting was used on the purpose of protection from cold and thermal insulation in Northern Scandinavia in A.C. 600’s as natural coating cover of roofs.
Although many green roofs were intensely applied in many buildings especially in Europe and the United States of America in the beginning of 20th century, efficient usage in trade and industry structures especially in terrace areas started in the 1960’s in Germany. Today, electricity production from solar energy with photovoltaic panels integrated over green roofs as an addition in Europe is adopted as a city policy and it is made to be constructed at a certain area in commercial structures of the countries such as Germany and France.
In our country roof of Küçükçiftlikpark car parking lot built by Istanbul Metropolitan Municipality in 1988 is included among the first applications. Also, Karum Business Center car parking lots roofs built in Ankara in the same years are from garden roofs, which are still alive and made by traditional method.
The roofs of the buildings, which are idle for years, are transformed into comfortable, functional and livable green areas by the development of the technology. The people use roofs and terraces by planting them both on ecological and aesthetic purposes for centuries in many countries of the world. This trend in our country rapidly increased in the latest years and our designers launched natural garden roofs for usage in over-car parking lot, top roof floor of the buildings or terrace floors in many projects such as public, hospitals, hotels, shopping malls, schools, business centers, social – mass housing. Garden roof applications made by gravel, which is a traditional method until 2000’s, replaced applications made by water retention drainage plates with developing technology.
Today green roofs are made systems according to details with greatly developed structure materials in technological aspects. Generally they consist of water repellent and root repellent insulation layer, humectant cover, drainage system, filters, slight garden roof soil, irrigation system and plant layer. Green roof may be created by using shallow or deep eased soil depending on the desire in flat terrace roofs as well as it may be applied both in flat and sloping roofs. 3 types of planted roofs are encountered.
Extensive Green Roof: They are thin, eased soil usage and little intense planted roofs. It consists of sedum type desiring little water and care with a shallow soil layer in the depth of 7-20. The weight of the system is 70-170 kg per m².
Intensive Green Roof: It consists of intense plants, in which thicker and relieved soil layer is used. Applications up to 20, 60 even 150 cm soil depth may be made. More options may be preferred for planting. It is a system appropriate for little tree and bushes with roots going deep. It requires a special irrigation and professional care. Its cost is naturally higher.
Sloping Green Roof: They are applications made with sedum type planting in maximum 10-15 cm soil thickness by using special non-slip covers and soil holder cellular partitions over roof repellant feature of water insulation in roofs with slope between 15–45 degrees. It should be preferentially preferred according to sedum planting grass cover type in terms of caring of sloping roof at a minimum.
So, why should we do garden roof?
Since it transforms into green cover by using rain water, it decreases excessive drainage intensity and waste network water load decreases.
It decreases air pollution and dust particles in the air. It is seen in the tests performed in the regions with less green cover that dust particles in the air is 3-7 times more compared to the regions with intense green.
Oxygen production increases, vapor transmission is high. It increases air quality. It naturally decreases carbon release.
It decreases heat island formation effects in the cities by means of its structure, which has high insulation level and does not do heat radiation. As a result of it, it reduces heating – cooling wastes, it increases urban comfort.
It absorbs noise, it provides sound insulation in urban aspect.
It disposes of greenhouse gases, it purifies heavy metals mixed in the rain water from air by keeping within the soil.
It is a recyclable material. Low energy is used in its application. Human power is sufficient.
It recovers natural soil lost in excavation stage with special mixtures added within as plant soil.
It contributes to increase of biological diversity and urban agriculture on the earth.
It creates architectural concepts with high design and aesthetic richness and integrated with green.
It protects the structure from UV rays, it protects the roof and carrier construction from mechanical damages. It provides fire protection of the structure at maximum with green areas.
While at least 50-60 m² of each 100 m² terrace roof area in Europe is today in a statues to design with green roof and solar energy systems, these rates are at the rate of 20-30 m² at us with incentives and new zoning law yet.
The latest point achieved in green roofs in construction and building materials sector in Turkey is Garanti Bank Technology Campus project, whose construction is completed in 2018; and Turkey leads the way in green roof market by means of soil repellant planted roof system solution applied in amorphous surfaces. This architectural structure is one of the international projects having the most special and specific garden roof applied as length in meters and variable, high slope not only in our country but also in Europe.