Passive solar design via bi-directional computational inference

This paper demonstrates a computational bi-directional energy, air flow and thermal comfort modeling approach to the design of passive solar buildings. Conventional simulation tools may be labeled as mono-directional in that they require a more or less complete design definition in order to derive performance indicators. However, for the purpose of passive solar design, it may be desirable to reverse this process: a bi-directional (or ''open'') inference mechanism would allow for the identification of those changes in the design variables that would accommodate a desired change in a performance indicator. The performance-to-design mapping process is an ambiguous one: the same performance (e.g. energy need of a building, temperature variations in a space, predicted percentage thermally dissatisfied people in the space) may be achieved by different design configurations (various wall and window dimensions/properties, building orientation/massing natural ventilation, etc.). To solve this ambiguity problem, the development described in this paper utilizes a preference-based approach that involves the formalization of various external or internal constraints and preferences (such as code and standard requirements, results of post-occupancy studies, individual priorities of designers and their clients, etc.) in terms of normalized numeric scales. A key point is that the preference functions are explicated to the user, are not static, and may be modified during the design process. The computational environment that we use to conduct bi-directional analysis consists of modeling tools for energy and air flow simulation, as well as thermal comfort analysis. These tools are integrated within a object-oriented space-based design support environment (SEMPER). After a brief review of the underlying preference-based approach for bi-directional analysis, the paper demonstrates an actual design session using the bi-directional thermal simulation tool. Specifically, a use-scenario is described in which the designer explores the trade-off between various design variables (e.g. glazing area, glazing type, and floor mass) in view of their implications for thermal comfort within a typical residential building. The paper concludes with a discussion of the potential and limitations of the bidirectional approach toward active convergence support for performance-oriented design development.