Green roof performance towards the cooling of buildings in tropical climate

Abstract

Due to the rapid urbanization, greenery is being rapidly destroyed. Urban Heat Island is one of the major adverse effects of lost flora. Green roof systems can be effectively used to control this issue" with a well planned urbanization. Green roof acts positively not only upon the climate of the city and its region but also upon the interior climate of the building beneath it. This will be very useful in the contest of saving energy required for providing thermal comfort for occupants in tropical climatic condition. This study investigated effects of extensive green roof on cooling of buildings. The main objective of the study was to investigate thermal performance of model buildings due to an extensive green roof. Naturally ventilated building and air conditioned building were represented by a model building “With cross ventilation condition” and “Without cross ventilation condition” respectively. A model building was constructed using flat cement fibre sheets as both roofing material and wall panels. The model building was exposed to direct sunlight throughout the daytime. Roof top was prepared for plant growth. Monitoring of indoor and outdoor temperature has been started in parallel with monitoring of plant growth. The vegetation coverage jvas quantified by using photographic technique. It was found that green roofs can be effectively used for the cooling of buildings. When the green coverage is increased the difference in the temperature between the indoor and outdoor also increases. With 77% green coverage, the extensive green roof cools center of the model building with cross ventilation by 1.75°C and that without cross ventilation by 2.0°C.