Fresh Air Requirement in HVAC (Ventilation Basics)

Fresh Air Requirement in HVAC (Ventilation Basics)

Fresh air is essential to maintain indoor air quality (IAQ), comfort, and safety in buildings.

Why Fresh Air is Required

Removes CO₂ and pollutants
Controls odor and humidity
Improves occupant health

Fresh Air Standards (ASHRAE 62.1 / NBC)

Person-Based

Office

8-10 L/s/person (17-21 CFM/person)

Conference Room

10-15 L/s/person (21-32 CFM/person)

Area-Based

Office Area

0.3-0.6 CFM/ft²
1.5-3 L/s-m²

Conference Room

0.5-1.0 CFM/ft²
2.5-5 L/s-m²

Example (Combined Calculation)

For an office of 100 m² with 10 persons:

Person-based = 100 L/s (≈ 212 CFM)
Area-based = 200 L/s (≈ 424 CFM)

Final Fresh Air = 200 L/s (≈ 424 CFM) (higher value considered)

Methods of Fresh Air Intake

Fresh Air Fan (FAF)
AHU with mixing box
DONATE
ERV / HRV

Key Point

Use both person + area method
Select higher value for design

Proper ventilation = Healthy + Energy Efficient HVAC System

Comments

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