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• This paper focuses on extensive green roofs and their effect on indoor thermal comfort in a housing project. • Coupled simulations were performed linking outdoor microclimate and indoor thermal comfort calculations. • A ceramic tile and a green roof were compared in an original site and a green site (with trees and grass). • The microclimate around the house affects the effect of the green roofs on indoor thermal comfort. A comprehensive understanding of the effect of green roofs on the indoor thermal comfort, under different microclimates, will help to identify key design aspects. In this study, which is the first of its kind in Brazil, the indoor thermal comfort for two different types of roofs, under different microclimates in Porto Alegre in Southern Brazil, have been compared. Coupled simulations using ENVI-met and EnergyPlus linked calculations of outdoor microclimate and indoor thermal comfort. The site was approximately 100 m by 100 m with 24 one-story, naturally ventilated semi-detached houses with an area of 39 m2. One of the houses, located approximately in the middle of the site, represented the building scale. In the original site (with no tree shadings), the substitution of the ceramic by the green roof led to an increase of 9.1% of the time within the thermal comfort zone. This study helps to bridge the current gap between thermal simulations in different scales. Moreover, this investigation concluded that green roofs performed better when in a green environment: for the summer season, with trees partially shading the roof, the green roof resulted in a reduction of the maximum operative temperature by 4.3 °C, whereas for the site without trees, the reduction was 2.8 °C. [ABSTRACT FROM AUTHOR]