Green roof is a technology that consists of the use of soil and vegetation installed in the roof of buildings, being a great solution to combat heat islands. Thus, this study aimed to compare micrometeorological changes and their effect on the energy balance of nonvegetated (slab) and vegetated building roofs by means of a simulation model calculated as a function of the reference evapotranspiration (ETo), determined by the Penman-Monteith method. This research was developed between February 1 and September 30, 2016, in the Charles Darwin Building's Parking Garage, Rio Ave Empreendimentos, Recife, PE, Brazil. For this, a weather station was installed on the external building slab. On the slab, sensible, latent, and soil heat fluxes corresponded to 75, 22, and 3%, respectively, of the energy balance. In the simulated green roof, these fluxes reached values of 6, 87, and 7%, respectively. The simulation model allowed determining the energy balance for the green roof, indicating a lower sensible heat flux (69%) and a higher latent heat flux (55%) when compared to those found in the slab.