A set of application programming interfaces (APIs) has been developed for the whole-building contaminant transport and airflow modeling software program, CONTAM. One API allows for the creation and modification of CONTAM building models to be incorporated into modelling workflows, and another allows other simulation tools and programming environments to dynamically link to and run CONTAM building models, interactively control their execution, and query for simulation results. These new APIs simplify the incorporation of CONTAM within building design and analysis frameworks and co-simulation workflows, and open possibilities for extending the current capabilities of CONTAM. We present an overview and motivation of these APIs and examples of their use, including development of a custom control algorithm, an enhanced sorption model, and integration with a three-dimensional architectural design platform and urban scale analysis tools.

Building modelers need simulation tools capable of simultaneously considering building energy use, airflow and indoor air quality (IAQ) to design and evaluate the ability of buildings and their systems to meet today’s demanding energy efficiency and IAQ performance requirements. CONTAM is a widely-used multizone building airflow and contaminant transport simulation tool that requires indoor temperatures as input values. EnergyPlus is a prominent whole-building energy simulation program capable of performing heat transfer calculations that require interzone and infiltration airflows as input values. On their own, each tool is limited in its ability to account for thermal processes upon which building airflow may be significantly dependent and vice versa. This paper describes the initial phase of coupling of CONTAM with EnergyPlus to capture the interdependencies between airflow and heat transfer using co-simulation that allows for sharing of data between independently executing simulation tools. The coupling is accomplished based on the Functional Mock-up Interface (FMI) for Co-simulation specification that provides for integration between independently developed tools. A three-zone combined heat transfer/airflow analytical BESTEST case was simulated to verify the co-simulation is functioning as expected, and an investigation of a two-zone, natural ventilation case designed to challenge the coupled thermal/airflow solution methods was performed.