This study presents the results of tests conducted in 2009 and 2010 on experimental sites installed on the roof of the Science and Education Building of the Wroclaw University of Environmental and Life Sciences. The aim of the analysis was to determine the retention capacity of green roofs and the runoff delays and peak runoff reduction during rainfall recorded in Wroclaw conditions.

The research shows that green roofs allow to reduce the volume of runoff stormwater in comparison to conventional roofs, that they delay the runoff in time and influence the reduction of the maximum runoff intensity, and thus may limit the impact of stormwater on the stormwater drainage and combined sewage systems.

The article shows the need to take into account the principles of sustainable development in the field of the revitalization of space, and point out green roofs as a tool in this process. It is presented in the light of the green city concept, and the criteria of the European Green City Index. The article shows the ecological, social and economic benefits of green roofs (starting from the retrieval of green areas in the urbanized space, the reduction of heat island effects, up to the integration function of green roofs), which is illustrated by a few case studies of applying green roofs within revitalization projects. The article indicates also legal incentives, as well as programs directed to the development of green roofs around the world, pointing out a range of factors to consider also for Polish cities.

Green roofs are increasingly popular in both new and modernised buildings. They significantly reduce the outflow of stormwater from buildings and change its composition. Wherever an urbanised area is equipped with a separate sewage system, usually stormwater goes directly to the receiver without treatment, which may affect the quality of water in the receiver. The article presents results of research carried out on the green roof of a building in Lodz, Poland. During rainfall, the flow rate from the roof was measured. With the use of the US EPA software Stormwater Management Model (SWMM) a model of the green roof was created and calibrated using rainfall data from the city’s pluviometric network. Based on the measurements of the roof runoff, as well as SWMM modelling, the degree of outfall reduction was determined. Samples of roof runoff were collected to study the characteristics of rainwater, including pH, electrical conductivity, organic compounds, nitrogen, phosphorus, and suspended solids. The results were compared with the quality of runoff from a traditional roof. Except ammonium nitrogen, values of the examined quality indicators was higher in the case of the green roof but the pollution load of almost all contaminants, except phosphorus, were lower due to a significant reduction in the volume of stormwater outflow (62–91%). The quality of stormwater discharged from the green roof improved with its age.