In the past, IT system design is mainly driven by two essential factors: technical merits and costs. Environmental consideration only emerges in most recent discussions under the label of green IT. As the evaluation of environmental and climate impact involves too many parameters, some of which are indirect and hidden, it is very hard to make rationale anal- ysis without the support of a holistic strategic analysis framework. In this paper, we pro- pose to extend the goal-oriented requirements modeling language, GRL, to model the rationality behind IT system design, in particular, how the environment related consider- ations come into play in such design decision making. It can be adopted as a strategic anal- ysis framework to facilitate concrete decision makings under different environmental settings. Example real world scenarios are used to illustrate how the proposed approach can help improve the state of the practice.