The NEBB Professional 2026 - Quarter 3

Recent updates also acknowledge CO2 DCV uncer tainties and incorporated: A better approach: Know the population & measure airflow rates

Note: even if CO2 sensors are used instead of counting, airflow measurement is still key to maintaining limits and pressurization.

For facility managers, the takeaway is clear.

The most reliable way to deliver proper ventilation is to base it on actual occupancy and to incorporate direct airflow measurements.

Special considerations for DOAS

In dedicated outdoor air systems (DOAS), accurate airflow measurement becomes even more critical. According to ASHRAE design guidance, ventilation performance in DOAS applications requires: • measurement at the zone level • control of airflow based on actual demand • accommodation for pressure and system variability Without measurement, verifying proper ventilation in these systems becomes difficult. Next steps for FMs As expectations around IAQ, energy performance and compliance increase, FMs should: • question reliance on CO2 alone as a control strategy • verify that ventilation aligns with actual occupancy • incorporate measurement where possible • trend and analyze data over time to validate performance DCV remains a valuable strategy, but only when imple mented with a clear understanding of its limitations.

Emerging and practical alternatives include:

• Occupancy-based inputs (e.g., badge systems, ticketing, scheduling data, people counters)

• Direct outdoor airflow measurement systems

• Integrated building controls that respond to re al-time conditions

For example, in a theater:

• ticket sales provide a direct number of occupants

• ventilation rates can be calculated based on known requirements of airflow rate per person

• minimum rates can be limited to the higher of the area airflow rate or the rate required for proper pressurization • maximum rates can be limited to the design outdoor airflow rates so that overventilation does not occur

• airflow rates are then adjusted for the actual oc cupancy — without waiting for CO2 to rise

As building performance expectations rise, ventilation must be measured and verified rather than assumed.

This approach eliminates inherent uncertainties, elim inates under- and overventilation, and reduces CO2 sensor maintenance related activities while allowing airflow measurement to validate rates.

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The NEBB Professional | Quarter 3 | 2026