The creation of building performance simulation models is time consuming and requires a great deal of expertise and building-specific knowledge. The total investment of resources required to construct a model strongly depends upon the size and complexity of the building under consideration, but in general the effort may be thought of as a four-step process: gather the necessary building information, convert this information into the format required by the simulation program, troubleshoot any issues that arise, and simulate the building. If the modeler needs to use more than one simulation program for the analysis process, then it is likely that much of the process must be repeated for each program. Even if no additional data are required (removing the need for the first step), the modeler will likely need to translate this information into a different form for each simulation program and the troubleshooting and simulation steps will require knowledge of the simulation program in use. This paper describes a "single model" approach, in which a more complex EnergyPlus energy model is used to generate a less complex CONTAM airflow model. This reduces the overall effort required to perform both analyses on a single building. The resulting airflow models are fully-functional and are suited for use in parametric simulation studies but by necessity are not as detailed as purpose-built models might be. The procedure uses a base energy model that is constructed with the open-source OpenStudio energy modeling toolset and then translated into a simplified airflow model using the OpenStudio software development kit. An example contaminant transport application, quantification of building security against chemical/biological extreme events, is presented and the advantages and limitations of this approach are discussed, along with possible future applications.