Thermal Evaluation of Green Roof Systems Containing Bottom Ash Growth Media

This paper presents a study on the use of furnace bottom ash (FBA) as a growth medium in green roof applications. Experimental tests were performed on three different green roof samples, involving FBA as the growth media and three sedum types (kamtchaticum, spurium, sexangulare) matched with it. Theoretical analysis was conducted for modeling the heat transfer through the green roof samples. Temperature readings at the surface center, bottom center, and bottom edge of each sample were recorded for 12 weeks with a data sampling frequency of 15 minutes. The results were compared with roofs without vegetation. These reference roofs are covered with black (EPDM), and white (TPO) roofing membranes. The study showed that green roof samples with FBA yielded better thermal performance compared to conventional roof membranes. However plant survival and coverage could be an issue in green roof systems using FBA if necessary amount of plant maintenance is not performed.