Adoption of an Integrated Design Process (IDP) to achieve Net Zero Energy Building (NZEB) targets is suggested by various studies, but there is a serious lack of pragmatic understanding of factors and relationships that affect its implementation in real-life projects. The focus of this study is to identify tangible (such as budget) and intangible (such as conflict of interest, expertise and experience, sense of ownership and occupant input) factors and relationships to help practitioners and researchers gain a better operational understanding of IDP implementation in actual projects. The study first identifies and organises factors and relationships into a systematic framework and then demonstrates the applicability of the framework using a case study. In the study, identification of previously studied factors and relationships is taken up through directed content analysis of literature, followed by semi-structured interviews with ten building experts to expand on existing knowledge providing new factors and relationships. Using Dedoose, factor frequency and co-occurrence analysis of audio and textual interview transcripts are conducted to obtain a total of forty-one unique factors and relationships. Lastly, framework validation is achieved using an actual IDP implementation case study - the new NZEB at the National University of Singapore (NUS). The framework is useful to design teams for training on IDP and design management, and to researchers for comparison of IDP implementation between projects.