Designing Building Ventilation to Exceed Codes and Standards
ASHRAE Journal, Vol. 67, no. 6, June 2025
Author:
Kishor Khankari
Abstract:
Good indoor air quality (IAQ) is essential for a healthy, comfortable, and productive work environment. Conventionally, dilution approaches are used to estimate clean air flow rates, which help reduce the level of indoor airborne contaminants. These approach assume instantaneous perfect mixing of ventilation air with indoor contaminants. Similar approaches are adopted in IAQ codes and standards for the specification of ventilation air flow rates at the space boundary or most commonly at the air outlets in the ceiling. However, the breathing zone of occupants, which is the most critical zone for IAQ, is located close to floor
Air is the primary carrier of heat, moisture, and airborne contaminants in indoor spaces. Therefore, in addition to the quantity of clean air, the indoor airflow patterns and flow paths of airborne contaminants play a crucial role in determining indoor air quality. Factors such as the layout of supply and return locations, the layout of spaces, and obstructions to airflow can impact airflow patterns and the distribution of temperature and airborne contaminants. It is nearly impossible to physically evaluate and optimize all these factors.
As demonstrated by several studies the science of Computational Fluid Dynamics (CFD) and the associated Spread Index metric can provide a feasible approach for evaluating and optimizing ventilation performance, even during the conceptual stage of design. While building codes and standards are important for ensuring that ventilation designs meet minimum requirements, they may not be optimum and cannot adequately address the impact of intricate indoor airflow paths on indoor air quality. To ensure a healthy indoor environment for all, a holistic approach, including a provision for a CFD-based performance path in the ASHRAE IAQ standards, would be beneficial.
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About the author
Dr. Kishor Khankari
ASHRAE Fellow, ASHRAE Distinguished Lecturer
Dr Kishor Khankari is the founder of AnSight LLC. As a specialist in Computational Fluid Dynamics (CFD), his passion for solving engineering problems and providing sound scientific solutions has led to innovations and optimized designs in the industry.
A noted expert in his field, he has a Ph.D. from the University of Minnesota and has published in several technical journals and trade magazines. As a well sought-after speaker Dr. Khankari makes regular presentations in various technical conferences and professional meetings worldwide.
