Desempenho do sistema de telhado verde como estratégia de condicionamento térmico passivo no semiárido alagoano

Abstract

In tropical countries such as Brazil, the roofing is responsible for part of the heat transferred to the internal environment, due to the large amount of solar radiation that falls on it. Controlling this incident radiation through the characteristics of the materials used in the roof may favor better conditions of comfort to the user. In this context, green roofs are an alternative, because part of the radiation is used by plants and not directly in the heating of the structure. In addition, they promote thermal inertia and evaporative cooling for buildings, bioclimatic strategies indicated for constructions in the city of Arapiraca, Alagoas. Thus, the objective of this dissertation was to analyze the performance of green roofs system as a passive termal conditioning strategy for Arapiraca (Brazilian semi-arid), studying the following aspects: the thermal performance of the green roof and a cover composed only of bare soil compared of conventional systems (slab, ceramic tile and fiber cement); the influence of the plant species and the presence/absence of vegetation in this performance; and the impacts of irrigation on the hygrothermal performance of the green roof. The method used was the monitoring in test cells of hourly data from temperature and humidity, internal and surface. The results showed the green roof with thermal amplitudes is lower than the bare soil and the conventional roofs, furthermore, higher values of external surface moisture and relative humidity of the internal air, especially in the daytime. Bare soil and green roof showed similar performance in the monitored variables due to their thermal transmittance values being close. They even reduced approximately 5.0ºC in the internal surface temperature, when they were compared to the waterproofed slab. The absence of vegetation on the green roof allowed greater thermal amplitudes in surface temperatures, reaching 4.0ºC higher than the amplitude of the external surface temperature founded in the green roofs. Comparing the species Zoysia japonica, Callisia repens and Desmodium triflorum, no significant differences in temperature and relative humidity of the indoor air were found. Regarding irrigation frequency, the differences in the hygrother mal performance of the test cells with daily, weekly irrigation and total suspension of irrigation were small and close to the precision of the equipment. For the semi-arid climate of the city under study, the green roof was efficient in avoiding the high thermal amplitude in the internal environment, an important aspect for obtaining thermal comfort. Above all, these structures could be used in buildings with daytime operation. Beyond that, the influence of the soil/substrate on the thermal performance of the green roof can be highlighted not suffering much influence from the plant species or the frequency of irrigation adopted.