Green roofs are an ecological approach to building construction, offering numerous environmental, energy, and economic benefits. Since 2012, the New Building Regulation has promoted the concept of “planted roofs,” encouraging their creation in new constructions or existing buildings with the incentive of height allowance. Specifically, according to the regulation, the maximum allowable height of a building can be increased by 1 meter if planting covers 50% of the roof. Additionally, the construction of main use spaces, with a maximum area of 35 square meters, is permitted if 80% of the roof is planted (roof space ratio of 1 to 5).
Despite the countless benefits of constructing such a space, there are some “myths” related to this topic.
Myth: A green roof will cause moisture problems in the building.
The special installations made on the roof will prepare and waterproof the roof surface before planting, preventing water infiltration. Contrary to common concerns, a green roof not only does not cause moisture issues in the building but can also protect the roof from potential erosion due to extreme weather conditions, while also improving the runoff of rainwater. During heavy rainfall, the flow of water is slowed down, and the green roof can retain up to 3/4 of the water volume, stabilizing groundwater levels and reducing the risk of flooding.
Myth: The cost of such a construction is exorbitant.
The cost varies depending on the type of green roof that will be created. Specifically, if the extensive type of green roof is chosen (lighter and less deep than the intensive type), the required installations are simpler and more economical, and frequent maintenance is not necessary. Additionally, in the medium term, the initial construction cost is fully offset, as the building’s residents benefit economically from the insulation provided by the green roof and from the extended lifespan of the roof due to the prevention of erosion (without needing further repairs). Lastly, the “Exoikonomo” program can subsidize up to 75% of the insulation work for the construction (planting is not subsidized).
Any work carried out must always comply with the structural study issued by the responsible engineer. Nevertheless, the type of construction chosen is crucial, as there are many innovative drainage materials and planting substrates that are very lightweight. Additionally, the protection from extreme weather conditions provided by a green roof significantly extends the building’s lifespan.
