Sustainability design involves the design of sustain- able software systems. There is a growing need to integrate sustainability issues into software development; therefore, many approaches have been developed in recent years. A widely used approach for sustainability design, the Sustainability Analysis Framework (SusAF), is applied in three cases, two industrial and one in academia. Following an exploratory, multiple case study research with workshops, interviews, and participant ob- servations, this study discusses the experiences of applying SusAF. The results reveal that SusAF provides a space to conceptualise definitions and a vocabulary for sustainability. It also allows for negotiations on sustainability issues, bringing a multidisciplinary perspective and facilitating tool-based communication. Future work aims to compare SusAF with other sustainability design approaches.