Book excerpt: A deep understanding of the implications of green roof retrofit is required amongst students and practitioners to make the decisions and take the actions needed to mitigate climate changes. Green Roof Retrofit: building urban resilience illustrates the processes undertaken to develop this new knowledge and thereby embed a deeper level of understanding in readers.Illustrative case studies and exemplars are drawn from countries outside of the core researched areas to demonstrate the application of the knowledge more broadly. Examples are used from the Americas (North and South and Canada), Oceania, Asia and other European countries.The book describes the multiple criteria which inform decision making and how this provides a way forward for making better decisions about green roof retrofit in different countries and climates.