In response to increasingly stringent energy performance requirements for buildings, the need for energy-efficient construction becomes ever more important. Although new construction technologies have emerged, thermal bridges are still common in new and especially in to-be renovated buildings. To facilitate analysing the effect of thermal bridges this paper investigates the development of a method to automatically integrate their effect into energy simulations. The developed workflow starts with integrating thermal bridges into Building Information Modeling (BIM) software. Subsequently, the thermal bridges are exported to the open source format Industry Foundation Class (IFC). Finally, a conversion of the IFC file to a readable file for the energy simulation software Modelica, using the ifc2modelica tool is shown. Furthermore, it investigates the impact of thermal bridges on different key performance indicators (KPIs) for both renovation and new build cases. This research aims at efficiently integrating thermal bridges in energy simulations during early design stages. The foundation for a BIM-library for standard thermal bridges has been developed, allowing an easy integration in existing BIM models with good simulation results.