A review of green roof incentives as motivators for the expansion of green infrastructure in European cities

City development for residential, commercial and transportation purposes contributes to the disappearance of green areas. Only in Austria, 15–25 ha of land are sealed every day (Pendl, Hüfi ng, Muerth, Tributsch & Jäger-Katzmann, 2009). The urban sprawl tendency only enhances this phenomenon. The development of biologically active areas leads to the loss of recreation areas and potential habitats. The biodiversity of the given land decreases and the proportional share of specifi c elements in the water and heat balance become distorted. According to the World Health Organization (WHO), the minimum green areas should be 50 m2 per urban agglomeration resident (Russo & Cirella, 2018). However, the reality is different. In many European cities, urban areas do not provide adequate space for green infrastructure. As a result, building green roofs, which are one of the green infrastructure solutions, is becoming increasingly perceived as an action with a benefi cial infl uence on the urban environment. Apart from the possibility to recreate biologically active areas in cities (partly, e.g. 50% in Poland), numerous studies confi rm the capacity of green roofs to retain rainwater and delay runoff, as well as to reduce the amount of pollutants in air, improve the microclimate and positively infl uence the urban heat island effect (Shafi que, Kim & Rafi q, 2018; Burszta-Adamiak, Stańczyk & Łomotowski, 2019). Another factor that is increasingly appreciated in cities, is the fact that green roofs provide friendly, green leisure spaces and improve the aesthetical values of buildings (Sutton, 2014). Other argument that supports their construction is the possibility to reduce carbon footprint in cities (Ugai, 2016) and direct water footprint (Fialkiewicz et al., 2018). Green roofs can also be included in the “smart city” Scientifi c Review – Engineering and Environmental Sciences (2019), 28 (4), 641–652 Sci. Rev. Eng. Env. Sci. (2019), 28 (4) Przegląd Naukowy – Inżynieria i Kształtowanie Środowiska (2019), 28 (4), 641–652 Prz. Nauk. Inż. Kszt. Środ. (2019), 28 (4) http://iks.pn.sggw.pl DOI 10.22630/PNIKS.2019.28.4.58