Green roofs are effective in cooling and mitigating urban heat islands to improve human thermal comfort

The present work was carried out in the city of Recife, Pernambuco State, Brazil, one of the largest coastal cities in Northeast Brazil (NEB). The thermal behavior of a roof slab was verified before and after the installation of a green roof through thermal images, as well as the characterization of the spatial variability of the temperature of its internal surface applying geostatistical interpolation models, with emphasis on the characterization of the environmental thermal comfort. From the temperature matrices extracted from the captured thermal images, statistical and geostatistical analysis was performed. The Human Comfort Index (HCI) was calculated for the indoor environment. The results demonstrate that the adoption of the green roof significantly reduced the slab inner surface temperature, provided by the vegetation presence. The model that best characterized the effects of the green roof presence on the slab was the exponential, with a strong degree of spatial dependence (DSD < 25%) and significant fit (R2 > 0.99). The characterization of the thermal variability of the indoor environment allowed identifying an average reduction in the HCI of 5.88 °C after the green roof installation, keeping it within the comfort zone in the range of 22.68 to 24.46 °C. Infrared thermography associated with geostatistical techniques proved to be effective in mapping and characterizing the slab temperature under green roof coverage, contributing to sustainable urban planning and the formulation of public policies to mitigate the effects of urban heat islands.