While much green roof research has been directed towards commercial and industrial buildings, less is known about the sloped roofs of residential buildings. The purpose of this study was to evaluate a pitched residential green roof system and determine its ability to retain stormwater runoff. In order to do this, 18 shingled roof models were constructed on three slope angles – 1°, 20° (5/12 pitch), and 40° (10/12 pitch) of which 9 were randomly fitted with a modular green roof system across three replications. The 42.1% mean stormwater runoff retention for the green roof systems of was significantly greater than the 18.3% for shingled roof decks. A residential product (Steep Paks®) performed within the conventional range of previous stormwater retention studies. The residential green roofs effectively reduced stormwater runoff during periods of light precipitation compared to periods of heavy precipitation. No difference was found in percent stormwater runoff retention between the three residential green roof slope angles.
The effects of roof age and plant coverage on insect communities were investigated between three green roofs located on the campus of Southern Illinois University Edwardsville. Insect collections were made using pitfall traps on green roofs that were established between 0.5 month and five years prior to insect collection. The green roof with the greatest insect collection rate was the oldest but intermediate in size and percent plant coverage. The oldest green roof had similar collection rates as a nearby ground-level rain garden; however measures of species diversity and evenness were greater in the rain garden.