This research investigates the impact of rooftop vegetation on the phenomenon of urban heat island (UHI) in hot-aired microclimates with an emphasis on housing projects in the context of Baghdad city. The methodology of this research relies on ENVI-met Headquarter 4.4.5 to create models that simulate and comparatively analyze the effect of rooftop vegetation on reduction UHI within housing projects. The analysis encompassed models of low-rise, mid-rise, and high-rise buildings. The simulated climatic parameters included the Predicted Mean Vote (PMV), air temperature, mean radiant temperature (MRT), reflected short-wave radiation, and humidity. The findings of this research indicated that rooftop vegetation can participate in the reduction of UHI phenomenon in housing projects, the most significant for almost all climatic parameters results were in low-rise and mid-rise buildings as compared to high-rise buildings.