If actual occupancy exceeds design occupancy, what is a likely consequence for ventilation and IAQ?

If actual occupancy exceeds design occupancy, what is a likely consequence for ventilation and IAQ?

• A. Ventilation rates automatically increase with no control.
• B. IAQ will automatically improve.
• C. If actual occupancy exceeds design occupancy, ventilation rates may be insufficient to maintain IAQ and energy performance.
• D. It will always improve IAQ.

Answer: (C)

Ventilation design is based on a target occupancy. If actual occupancy runs higher than what was planned, the fixed outdoor-air supply and the control scheme may not provide enough fresh air to dilute indoor contaminants and CO2, so IAQ can suffer. More people also generate more heat, moisture, and pollutants, which means the system may need to move more outdoor air to maintain acceptable IAQ and comfort. If the system can’t increase ventilation adequately—or doing so would exceed its energy constraints—the result is not only poorer IAQ but also a potential drop in overall energy performance, since you’re trying to meet IAQ with a fixed or insufficient ventilation rate. That’s why this scenario is described as ventilation rates may be insufficient to maintain IAQ and energy performance.

Ventilation design is based on a target occupancy. If actual occupancy runs higher than what was planned, the fixed outdoor-air supply and the control scheme may not provide enough fresh air to dilute indoor contaminants and CO2, so IAQ can suffer. More people also generate more heat, moisture, and pollutants, which means the system may need to move more outdoor air to maintain acceptable IAQ and comfort. If the system can’t increase ventilation adequately—or doing so would exceed its energy constraints—the result is not only poorer IAQ but also a potential drop in overall energy performance, since you’re trying to meet IAQ with a fixed or insufficient ventilation rate. That’s why this scenario is described as ventilation rates may be insufficient to maintain IAQ and energy performance.