This report discusses green “living” roofs and “cool” highly reflective roofs—building technologies that may offer solutions to ameliorate urban heat island effects and its consequences. This report has a relatively narrow goal: to focus on why these particular technologies may be incorporated into strategies for urban heat island mitigation, we review research assessing their environmental impact. We discuss the literature describing the effects of these “smart” rooftops on ambient air temperatures, energy use, and air quality. We briefly review cost-benefit analyses of these strategies and provide some initial insight into why urban heat island mitigation should be encouraged in New York City in light of these findings.