Estudo comparativo do desempenho térmico de telhados verdes com diferentes materiais drenantes em Curitiba-PR

Abstract

The present work aims to quantify the difference in thermal performance of an extensive green roof typology, when the material used in the drainage layer is changed, in the climatic conditions of the city of Curitiba-PR. In addition, analysis regarding the vegetation cover degree and volumetric water content of the substrate were carried out. Three green roof systems were studied, which differed in relation to the material used in the drainage layer: expanded clay (ARG), drainage geomembrane (GD) and drainage and water storage geomembrane (GDA). Prototypes with and without vegetation were built for each green roof system. Test cells (modules) were used for the thermal monitoring: 3 experimental modules with green roof (ME-ARG, ME-GD, ME-GDA), and a control module (MC) (reference). The thermal monitoring was performed between February and May 2020. In this period two configurations were alternated: experimental modules with vegetation cover (Series V), and without vegetation cover (Series S). The parameters adopted for the evaluation of the thermal performance were characteristic temperatures, time lag, decrement factor and average heat loss/gain potential. The results allowed to establishment of a hierarchy among the studied green roof systems, although the differences were small. In the case of the city of Curitiba, where there is a predominance of thermal discomfort conditions due to the cold, it is considered that the best thermal performance was obtained by the ARG system, followed by the GD, and lastly by the GDA. The system with expanded clay in the drainage layer was the one that promoted a greater reduction in the indoor air thermal amplitude of the, compared to the outdoor air. Regarding the thermal delay, in general there were no differences between the green roof systems. The ME-ARG showed higher heat gain potential values compared to the other experimental modules. Considering the S Series (without vegetation), the ME-GD and ME-GDA had a heat gain potential about 35% and 72% lower than ME-ARG, respectively. Considering the Series V, the MEGD and ME-GDA had a heat gain potential about 40% and 63% lower than ME-ARG, respectively. No direct relationship was identified between each of the green roof systems studied, and the evolution of the values of vegetation cover degree, as well as of substrate volumetric water content.