Roofs are large surfaces in the city that can be used to increase biodiversity. Next to aesthetic advantages there are is a major financial plus. German green roof specialist Optigrün has made an analysis of costs and benefits with 10 financial highlights:

1 No extra constructive effort compared with the usual gravel roof
2 Double life span of roof layers (up to 50 years) when protected by vegetation
3 Root protective layers have the same price as  normal water barriers
4 Extra cost for maintanance (12 EUR/m2 vs. 7 EUR/m2 for a gravel roof) is compensated
5 Lower local taxes may apply due to capacity of water retention
6 Intensly planted green roofs save green compensation measures on the ground
7 No rain water retention basin needed due to retention on the roof (saves min. 10 EUR/m2)
8 Green roofs insulate and lower heating costs.
9 6-8% higher revenues in rents or sales of property with green roofs.
10 Subsidies lower investment costs.

Read the entire analysis with more detailed costs and download the pdf (in German only150703 Optigruen-Kosten-Nutzen-Analyse ).