P4. Design Methods & Guidelines for Natural Ventilation in California > Background

Natural ventilation is being increasingly proposed as a means of saving energy and improving indoor air quality in commercial buildings, particularly in the "green buildings" community. These proposals are generally made without any engineering analysis to support the claimed advantages. In addition, design approaches are not available in this country to incorporate natural ventilation into commercial building system designs.

While natural ventilation is becoming more common in Europe, significant questions exist concerning its application in U.S. commercial buildings. These questions include the reliability of the outdoor air ventilation rates, distribution of this outdoor air within the building, control of moisture in naturally ventilated buildings, building pressurization concerns, and the entry of polluted air from outdoors without an opportunity to filter or clean it. Some climates within California are probably well suited to natural ventilation, but many of these same questions must be addressed for these locales. The NIST multi-zone airflow and indoor air quality (IAQ) analysis model, CONTAM, is capable of addressing these and other issues related to natural ventilation in buildings. In addition, the airflow calculation capabilities of CONTAM can serve as the basis of a natural ventilation design tool, enabling wider use of natural ventilation in a technically sound manner.

NIST currently has projects to investigate the potential of natural ventilation in U.S. commercial buildings and to validate the ability of CONTAM to correctly predict air flows in naturally ventilated buildings, providing a solid basis for extending this work to California-specific issues and buildings.

Natural ventilation has the potential to significantly reduce the energy cost required for mechanical ventilation of buildings. These natural ventilation systems may reduce both first and operating costs compared to mechanical ventilation systems while maintaining acceptable indoor air quality. Also, some studies have indicated that occupants perceived better indoor air quality with natural ventilation than mechanical ventilation. Improving indoor environmental conditions can also potentially increase occupant productivity by reducing absenteeism, reducing health care costs, and improving worker productivity.

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