With current energy analysis tools, architects and engineers cannot rely on the results of energy analyses because they do not report their level of precision. In addition, current tools also do not deliver feedback in real time. Thus, this research addresses the challenge of obtaining feedback in real-time while gradually increasing precision along design stages. For this purpose, this study merges parametric modelling (PM) technologies and the performance-based design (PBD) paradigm into a general design model. The model is based on a parametric and an energy analysis model that share the parameters of a building. The modular architecture of the model involves four main function types: an input processor, optional analysis functions embedding different calculation methods, a decision-maker, and a report generator function. For every step of the design evolution, the decision-maker function generates a specific tree of analysis functions.