What input determines the flow rates in a ventilation calculation?

• A. Wall color.
• B. Room volume and desired ACH determine flow rates.
• C. Outside temperature only.
• D. Number of windows only.

Answer: (B)

Ventilation flow rates are determined by the size of the space and the target number of air changes per hour. The usual relationship is Q = ACH × Volume, where Q is the flow rate, ACH is the desired air changes per hour, and Volume is the room’s volume. For example, a 50 m³ room with a target of 6 ACH requires 300 m³/h of airflow (about 176 CFM). Wall color contributes nothing to the calculation, and outside temperature or the number of windows don’t set the required flow rate for a design ACH—they can influence actual performance or energy use, but the fundamental inputs to determine the needed flow are room volume and desired ACH.