Uncovering the structural relationships among transaction costs in nearly zero energy building projects

Transaction costs are widely recognized as a hidden constraint on scaling Nearly Zero Energy Buildings (NZEBs), yet existing studies largely treat them as isolated items and overlook how they interact across stages and stakeholders. This study adopts a structural perspective to examine transaction cost interactions in Chinese NZEB projects. Based on 36 transaction cost elements identified in prior empirical work, we conducted a two-round Delphi survey with 23 experienced practitioners to elicit perceived directional relationships and construct a consensus-based structural self-interaction matrix. An integrated ISM–MICMAC–SNA approach was then applied to identify the hierarchical structure, driving–dependence categories, and key nodes in the network of transaction cost elements, complemented by Louvain community detection. The analysis reveals a ten-level structure that can be grouped into three functional zones and yields four main findings. First, transaction costs in the bottom driving zone are mainly borne by developers, especially those related to consultant selection and contract negotiation. Second, transaction cost determinants show a hierarchical pattern, with asset specificity dominating the lower levels and uncertainty becoming more prominent in the upper levels. Third, construction-stage transaction costs are not structurally isolated. In the expert-consensus model, they are linked to perceived dependencies from the concept and design stages through consensus-based directional relationships. Fourth, the study identifies twelve key transaction cost elements and groups them into five categories: partner selection, contract negotiation, technical solution development, certification document preparation, and construction change and dispute management. These findings clarify perceived dependencies and reachability patterns among transaction cost elements and provide a basis for proposing prioritized mitigation strategies in NZEB delivery.