Influence of irrigation frequency in green roofs on the hygrothermal performance of buildings in semi-arid region

Abstract

Maintenance is essential for all green roofs, including pruning and irrigation. For the latter, the literature presents some important guidelines, such as the need for irrigation during the stabilization phase, watering only during the driest periods and suitable for the specific needs of each plant species. Although precipitation reduces costs and the need for irrigation, in arid and semi-arid regions, irrigation is necessary for the survival of vegetation. Thus, this study aimed to analyze the influence of irrigation frequency on the hygrothermal performance of an extensive green roof during the hot and dry period of a tropical climate (As). Air temperature and relative humidity data were monitored inside test cells with green roofs of Zoysia japonica species installed on the roof for 29 days, with three irrigation treatments: no irrigation, weekly irrigation, and daily irrigation. The water deficit in the roofs without irrigation and weekly irrigation reduced plant growth and leaves became wilted, dry, and brownish in color, while daily irrigation kept vegetation healthy during monitoring. In the average values for the entire campaign, the green roof with daily irrigation reduced the indoor air temperature by 0.4 ºC and increased the indoor relative humidity by 4.5%, compared to the green roof without irrigation. It can be concluded that irrigation had a greater influence on the indoor relative humidity of the test cell, with little effect on reducing indoor air temperature.