Integrating novel software systems in our society, economy and environment can have far-reaching effects. As a result, software systems should be designed in such a way as to maintain or improve the sustainability of their intended socio-technical systems. However, a paradigm shift is required to raise awareness of software professionals on the potential sustainability effects of software systems. While Requirements Engineering is considered the key for driving this change, requirements engineers lack the knowledge, experience and methodological support for acting as facilitators for a broader discussion on sustainability effects. This paper presents a question-based framework for raising awareness of the potential effects of software systems on sustainability, as the first step towards enabling the required paradigm shift. An evaluation study of the framework was conducted with four groups of computer science students. The results of the study indicate that the framework is applicable to different types of systems and helps to facilitate discussions about the potential effects that software systems could have on sustainability.