Impact of green roof on human comfort level and carbon sequestration: A microclimatic and comparative assessment in Dhaka City, Bangladesh

Abstract

Abstract The study determines the impact of rooftop greening in an urban residential area in the microclimate context in Dhaka City Corporation, where the level of carbon sequestration from a green roof of an existing building and it s ability to reach the human comfort zone is focused. The study showed the nature of temperature variation between the green-roofed and bare-roofed buildings. Ten stations were chosen from the study area, where 20 buildings were studied, taking two neighboring buildings (a green- and a bare-roofed) from each station. Air temperature, relative humidity, and air velocity were collected from all floors and rooftops of the selected buildings. The Discomfort Index and Robaa Index have been measured to detect the human comfort zone. Annual carbon sequestration by the plants of the green rooftops was assessed. Findings revealed a significant difference (1o\xa0~\xa03.5\xa0°C) of the air temperature between the adjacent bare-roofed and green-roofed buildings. The thermal difference was significant during diurnal hours. The Discomfort Index and Robaa Index were lower in the green-roofed buildings than those of bare-roofed buildings. The annual carbon sequestration in the green roofs ranged from 20.6 tC/ha to 125.4 tC/ha, whereas the equivalent CO2 ranged from 84 to 460\xa0t/ha.