CSLB C-20 HVAC ContractorVentilation and Air DistributionHard
A commercial office space measuring 2,000 sq ft has a design occupancy of 20 people. Using the ASHRAE 62.1 Ventilation Rate Procedure default rates of 5 CFM per person plus 0.06 CFM per square foot for office space, what is the minimum required outdoor air ventilation rate?
- A120 CFM
- B100 CFM
- C220 CFM
- D340 CFM
Show answer & explanationAnswer & explanation
Correct answer: C. 220 CFM
ASHRAE 62.1 combines a people-based component and an area-based component: (5 CFM × 20 people) + (0.06 CFM/sq ft × 2,000 sq ft) = 100 CFM + 120 CFM = 220 CFM total outdoor air.
Why the other options are wrong
- A. This is only the area-based component, ignoring the occupant-based requirement.
- B. This is only the people-based component, ignoring the area-based requirement.
- D. This value overstates the requirement and does not match either component or their sum.
ASHRAE 62.1 Ventilation Rate Procedure
Commercial ventilation requirements combine a per-person outdoor air rate and a per-area outdoor air rate, both of which must be added together to determine minimum outdoor air CFM.
- Rp = CFM per person (varies by space type)
- Ra = CFM per sq ft (varies by space type)
- Total OA = (Rp × people) + (Ra × area)
Memory trick: 'People plus space, both get a place in the sum.'