Air quality, climate change, water supply, soil protection, biodiversity,
and the natural scenery are subject to public protection. These natural
resources are irreplaceable in terms of enhancing the quality of life,
and common urban architecture does not always address these issues adequately.
Local authorities and city councils have realized the dilemma and, hence,
promote Green Roof projects in compensation for the increasing exploitation
of natural resources.
Direct financial incentives, reduced stormwater taxes, density relief and regulatory measures, are some of the many greenroof-policies which can be used to encourage Green Roofs and promote the fast expansion of the Green Roof market. In particular, Germany has done a lot of pioneering work in supporting roof greening with various innovations over the last 20 years.
Some city councils and local authorities grant direct financial support for Green Roof projects. In many cases the financial subsidies vary between 10€ and 20€ per m2. Other communities pay a fixed sum for the entire Green Roof, which varies between 25% and 100% of the material and installation costs. In general, the support programmes fix certain quality criteria for the Green Roof build-up. This guarantees that the installed Green Roofs fulfill all of their ecological functions.
Many towns in Germany have introduced special stormwater taxes. The division of stormwater and sewage taxes, in effect, promotes natural rainwater management. For example, large sealed surfaces like car parks of big shopping centres or industrial areas often stress the local sewerage systems with very high rainwater run-off; and based on the causation principle, stormwater taxes make the responsible parties participate in the disposal costs. On the other hand, Green Roof areas with high water retention capacity are rewarded with fee reductions up to 50%. In the case that no stormwater is drained-off from the property into the sewerage system, the bonus can reach even 100%.
Green Roofs can mitigate damage to nature and landscape caused by sealed development areas. This mitigation parallels the Federal Nature Protection Act, which requires, that development should avoid any unnecessary damage to nature and that any unavoidable damage should be compensated for, preferentially, on site. There is no doubt about the compensatory effects of Green Roofs for damages in the natural balance of water, soil, air, climate, flora and fauna.
Some local authorities make Green Roofs mandatory within new development areas. The positive effects, for both the community and the inhabitants of the modern estates, are striking. Besides the broad range of private and public benefits, the sewerage system and water reservoirs within the development area can be designed on a smaller scale due to the evaporation and high water retention capacity of Green Roofs. This leads to lower public expenses for the construction and maintenance of the sewerage system and, consequently, lower stormwater taxes for the general public.