This study departed from a research basis being somewhat lacking in the context of green building certification and especially the two-folded problem, regarding the characteristics of the network of business relationships and how an energy supply company should exploit opportunities in this network context and its relationships. As such, the purpose of this study is to investigate and analyse the network context and its business relationship characteristics, as well as to present recommendations of how an energy supply company can engage green building certification and cope with the business relationships in order to exploit business opportunities. Based on previous research regarding the real estate industry, energy service industry and the construction industry, a well-founded literature base could be extended further by applying theoretical concepts related to business relationship elements and strategy-making. The nature of green building certification and to fulfil the purpose of the study, called for a qualitative research strategy performed through a multiple-case study design. This led to the investigation of four certification projects, subject to certifications in the systems of EU GreenBuilding and Miljöbyggnad, where the most important actors, relationships and project contents constitute the empirical data. The findings of this thesis suggest that the relationships are characterized as having a short-term focus and an avoidance to become interdependent. In this manner elements such as commitment and adaptation are shown as rather shallow, where actions of commitment are not typically short-term sacrifices for a long-term mutual benefit and adaptations mostly occur with respect to specific projects. The adaptive behaviour is also more or less explained as a standardized procedure, avoiding relationship specific investments. Trust is an important element mostly in order to reflect the competence of the counterpart, where previous successful projects indicate the skill and knowledge. Despite the characteristics of the relationships, the benefits of long-term, high involvement, cooperative relationships were highlighted as good aspects to consider in this context. These characteristics, along with outspoken market demands, acted as the basis for the development of recommendations for an energy supply company in terms of a step-wise action framework. In this sense, the first acknowledgement of the framework is that the current position related to green building certification projects of an energy supply company is rather unestablished, with only one exception found. This implies a strategic approach in terms of understanding how to develop and maintain their business relationships, with respect to the previously mentioned characteristics. Through a successful utilization of the action framework (with respect to certain barriers to overcome), this thesis emphasizes a wide range of opportunities such as to have a proactive approach, maintain interactions between projects, to develop the knowledge, to offer a holistic approach and to utilize long-term cooperative relational benefits. The analysis and framework is highly suitable when applied by an energy supply company, but the authors also argue for the findings to be of relevance also for other practitioners in the context of green building certification. In addition, the authors believe that the orientation of this thesis might be a trigger for future similar research approaches, applied in different contexts.