Laboratory and Mathematical Modeling of Green Roof and Different Color Roofs

Several studies were compiled using data from physical models of green and black surfaces in the lab and the Cooper Union (CU) roof as well as green roof studies of the Javits Green Roof (JGR) measured over a six-year period. Observations were made with weather stations, custom designed draining systems and three partial flumes each equipped with a pressure transducer and weighing lysimeters. An infrared camera was used at the CU and JGR to collect thermal images to determine the effectiveness these roofs had for thermal buffering. A multiple regression curve was calculated relating the lysimeter mass and five independent variables, with the precipitation runoff and retention time being the most important variables. The surface of the black roof was compared to white and green roofs at CU. The temperature was significantly higher (over 70 °C) on the black roof clearly showing the advantage of using a green roof. The ET was calculated on the JGR using the Penman-Monteith (P/M) equations. The runoff hydrograph for the JGR was constant with an increase in precipitation and storage when the hydrograph dropped in response to the precipitation and storage. When the plots (185 square meters at JGR) were irrigated, the dry plots always had higher temperatures (above 15 °C during summer daytime). The ET is the controlling factor for temperature reduction on a vegetated green roof as shown in the JGR data. The relative humidity (RH) was measured in the CU lab and on the JGR and showed similar results. The RH dropped during higher temperatures and recovered at lower temperatures. The results of these studies at CU and JGR clearly show the benefits of using a vegetated green roof.