A report published by the National Research Council defined the research on understanding and quantifying the value of infrastructure systems to the stakeholders - and how this value is impacted by the various planning and design decisions - as a national imperative. There is still a lack of understanding and formalized modeling of what different stakeholders value (e.g., energy conservation) in infrastructure systems and how to valuate (i.e., quantify the worth) infrastructure systems based on these values. In prior work, the authors proposed an axiology [theory of value (worth)] based mathematical model to quantify the value of an individual building component. In this paper, the authors propose a mathematical model for quantifying the value of a building system based on the values of the individual components that comprise this building system, and how these components physically integrate together. The proposed model is theoretically grounded in axiology and integration theory. It was initially validated through a case study. The model could provide more explicit understanding of how the components of a building system physically integrate together to fulfill stakeholder values and could facilitate value-sensitive decision making by embodying stakeholder values into project planning towards better synergy between human values and the built environment.