Urbanization increases the importance of urban infrastructures, with computer models and simulation being important tools for their planning and management. Human factors are increasingly included into infrastructure models, creating socio-technical models. This paper proposes a novel framework for selecting these social (sub-)models. For this, requirements analysis of the technical system is used to identify critical physical parameters. The impact of different assumptions in the social model on the critical physical parameters are determined using simulation and hypothesis testing. This impact is used to determine the relevance of the differing assumptions and to select the right social model. Finally, a preliminary case study of the water distribution system of Darmstadt, Germany, is used to show the efficacy of the framework by comparing two water demand models. The results of the case study show, that the framework can be used to quantify the relevant system behavior and test the significance of model assumptions.