Comparison of hygrothermal performance of test cells with green roofs using three plant species in tropical climate (As)

Abstract

The literature points out that seasonal changes in climate and the characteristics of plant species can influence the thermal performance of green roofs. This study presents an analysis of the influence of plant species on the hygrothermal performance of test cells with extensive green roofs, in the wet and dry seasons of a tropical climate (As). Air Temperature and relative humidity data were collected from the test cells, one day for each season: wet (08/29/2019) and dry (11/14/2019) in Arapiraca-AL. Desmodium triflorum, Callisia repens and Zoysia japonica were the plant species analyzed. In the wet season, the differences between Desmodium triflorum and Callisia repens were not significant, despite the distinct vegetation cover. Partial substrate coverage by Desmodium triflorum, metabolism and color of Callisia repens allowed for higher air temperatures and lower relative humidity than test cell with Zoysia japonica (maximum differences of 0.60ºC and 7.8%). In the dry season, Zoysia japonica and Callisia repens did not have significant differences in relative humidity, but Zoysia japonica had a lower air temperature (maximum difference of 0.56ºC) because its rhizomatous morphology can reduce heat exchange between the green roof and environment. Desmodium triflorum did not survive the dry season due to its seasonality. In general, Zoysia japonica performed better than other species in both seasons. However, tests of other species and a longer data campaign may allow for more accurate conclusions and lead to guidance on plant species suitable for green roofs in the climate under study.