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How to Size a Ventilation Fan | A Practical Guide

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How to Size a Ventilation Fan | A Practical Guide from AOSAIR

Selecting the correct sizeventilation fanis key to achieving optimal air quality, energy efficiency, and comfort in any space — whether residential, commercial, or industrial.

In this guide,AOSUN explainshow to size a ventilation fanstep-by-step, helping you make informed decisions for your next project.

Why Fan Sizing Matters

✅ Ensures adequate air exchange
✅ Maintains indoor air quality (IAQ)
✅ Prevents moisture buildup and mold
✅ Enhances occupant comfort
✅ Reduces energy waste
✅ Helps comply with building codes

Key Concepts: Airflow & Air Changes

✔️ Airflow Rate (CFM / m³/h)

  • CFM= Cubic Feet per Minute (used in US)

  • m³/h= Cubic Meters per Hour (used in Europe/Asia)

These units measure how much air the fan moves.

✔️ Air Changes Per Hour (ACH)

  • ACH refers to how many times the air in a room is replaced per hour.

  • Recommended ACH depends onroom type and use(see table below).

Step-by-Step: How to Size a Ventilation Fan

1️⃣ Measure the Room

Forrectangular rooms:

Length × Width × Height = Room Volume

Example:
A 5m × 4m × 2.5m bathroom →
5 × 4 × 2.5 =50 m³

2️⃣ Determine Recommended ACH

Room Type Recommended ACH
Bathroom 10–15
Kitchen 15–30
Office 6–12
Living room 6–10
Bedroom 4–8
Warehouse 6–20
Workshop 15–30
Gym / Fitness 10–20

3️⃣ Calculate Required Airflow

Required airflow (m³/h) = Room Volume × ACH
Example (bathroom):
50 m³ × 12 ACH = 600 m³/hrequired airflow

4️⃣ Convert Units (if needed)

  • To convertm³/h → CFM:

CFM = m³/h ÷ 1.699

  • To convertCFM → m³/h:

m³/h = CFM × 1.699

5️⃣ Select a Suitable Fan

Choose aventilation fanrated for at least the required airflow:
✅ Factor in duct losses (add ~10–20%)
✅ Consider noise level requirements
✅ Ensure compatibility with duct size

Practical Tips

✅ Always round up airflow to ensure sufficient ventilation
✅ For long duct runs → select fans with higher static pressure capability
✅ For noise-sensitive spaces → choose low-noise or EC motor fans
✅ For retrofit projects → verify available installation space

Common Mistakes to Avoid

❌ Using undersized fans → poor ventilation, mold risk
❌ Oversizing excessively → noise & energy waste
❌ Ignoring duct layout → airflow loss
❌ Not accounting for special equipment (e.g. in kitchens, workshops)

How AOSAIR Supports Fan Sizing & Selection

AOSUNFAN assists:
✅ HVAC contractors
✅ Architects and designers
✅ Builders and developers
✅ OEM partners

We provide:
✅ Fan sizing consultation
✅ Technical data sheets
✅ OEM customization
✅ Project-based product recommendations

Need Help Sizing Your Next Ventilation Fan?

Explore ourProducts pageorcontact us here.

Our team can help you:
✅ Select the optimal fan for your space
✅ Customize airflow performance
✅ Ensure compliance with project requirements

Conclusion

Proper fan sizing ensureseffective, efficient, and compliant ventilation— saving you costs and ensuring occupant comfort.
AOSUNFAN is ready to support your ventilation projects — contact us today for expert guidance!


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