A wetland roof is a special type of extensive green roof. The roof is evenly planted with wetland or marsh plants, which will be regularly irrigated on a daily basis. Besides the aesthetic aspect, this particular type of roof may also offer significant functional advantages.
Wetland roofs are natural air-conditioning systems. During the spring and summer months, the heat of the rooms below will be eliminated by the evaporation and plant transpiration of the water. When it becomes colder in autumn or winter, a wetland roof is, due to its additional heat insulating effect, an excellent protection against an extensive heat loss.
"There is increasing interest worldwide in the decentralized treatment of grey water. Since ground-level areas are generally costly, grey-water treatment can also be carried out using helophyte mats on the roofs of buildings as an alternative. Alongside the water treatment itself, this process also has a positive effect on the indoor climate in the building. In a test carried out under realistic conditions, it was shown that a helophyte mat with a root-layer depth of 0.1 m and with hydraulic loads per unit up to 15 L m−2d−1 is suitable for treating typical grey water from a residential building."
At the Helmholtz Centre for Environmental Research (UFZ) in Leipzig, Germany, a research green roof is currently under construction (2019), consisting of a reference area of gravel, an extensive green roof, a wetland roof and an evaporation-intensive green roof (80.5 m² each).
Further information can be found at www.ufz.de/forschungsgruendach (In German)