Using coupled energy, airflow and indoor air quality software (TRNSYS/CONTAM) to evaluate building ventilation strategies

Building energy analysis tools are available in many forms that provide the ability to address a broad spectrum of energy-related issues in various combinations. Often these tools operate in isolation from one another, making it difficult to evaluate the interactions between related phenomena and interacting systems, forcing oversimplified assumptions to be made about various phenomena that could otherwise be addressed directly with another tool. One example of such interdependence is the interaction between heat transfer, inter-zone airflow, and indoor contaminant transport. To better address these interdependencies, the National Institute of Standards and Technology has developed an updated version of the multi-zone airflow and contaminant transport modeling tool, CONTAM, along with a set of utilities to enable coupling of the full CONTAM model with the TRNSYS simulation tool in a more seamless manner and with additional capabilities that were previously not available. This article provides an overview of these new capabilities and applies them to simulating a medium-size office building. These simulations address the interaction between whole-building energy, airflow, and contaminant transport in evaluating various ventilation strategies including natural and demand-controlled ventilation. Practical application: CONTAM has been in practical use for many years allowing building designers, as well as indoor air quality (IAQ) and ventilation system analysts, to simulate the complex interactions between building physical layout and HVAC system configuration in determining building airflow and contaminant transport. It has been widely used to design and analyze smoke management systems and evaluate building performance in response to chemical, biological, and radiological events. While CONTAM has been used to address design and performance of buildings implementing energy conserving ventilation systems, e.g. natural and hybrid, this new coupled simulation capability will enable users to apply the tool to couple CONTAM with existing energy analysis software to address the interaction between IAQ considerations and energy conservation measures in building design and analysis. This article presents two practical case studies using the coupled modeling tool to evaluate IAQ performance of a CO2-based demand-controlled ventilation system under different levels of building envelope air tightness and the design and analysis of a natural ventilation system.