The majority of green roofs consist of Sedum-based plantings (hereafter referred to as Sedum) which are non-native to where they are widely deployed. Sedum has time and again been shown to outperform grasses and wildflowers (hereafter referred to as non-Sedum) in survival and cover on extensive green roofs. However, some studies have found that Sedum is unable to perform green roof functions as well as some non-Sedum plants. The growth in peer-reviewed literature on green roofs in the last few decades has prompted this meta-analysis to assess Sedum relative to non-Sedum performance. Here, we compare the standard effect sizes of Sedum to non-Sedum performances for three criteria on extensive green roofs: i) survival, ii) roof cooling, and iii) stormwater management.
Results/Conclusions
A total of 90 studies out of the 186 studies that were reviewed examined survival, cooling, and/or stormwater management of green roof plants. A large proportion of studies were conducted in North America (46%) and Europe (37%), only 18% were conducted elsewhere. We found that Sedum does survive better than non-Sedum on extensive green roofs, but there was no pattern in roof cooling and stormwater management. A lack of consistent metrics and methodologies when measuring green roof functioning is what future researchers and industries can work together to standardize.