How to Choose the Right Bathroom Exhaust Fan
Need a new bathroom fan? This guide explains CFM ratings, sone levels, and sizing to select the perfect exhaust fan.
Related: Broan-NuTone Brand Guide | Glossary | FAQ
Why Bathroom Ventilation Matters
Proper ventilation prevents mold and mildew, removes odors, reduces moisture damage, and improves indoor air quality. Most building codes require exhaust fans in bathrooms without windows.
Understanding CFM (Airflow)
CFM (Cubic Feet per Minute) measures how much air the fan moves. Higher CFM = more ventilation power.
CFM Calculator
| Bathroom Size | Minimum CFM | Recommended CFM |
|---|---|---|
| Under 50 sq ft | 50 CFM | 70-80 CFM |
| 50-100 sq ft | 1 CFM per sq ft | 1.5 CFM per sq ft |
| Over 100 sq ft | 1 CFM per sq ft | Add 50 CFM per fixture |
Quick formula: Length x Width = Square Footage. A 10x8 bathroom (80 sq ft) needs at least 80 CFM.
Understanding Sones (Noise Level)
Sones measure how loud the fan sounds. Lower = quieter.
| Sone Rating | Sound Comparison | Recommendation |
|---|---|---|
| 0.3-0.5 sones | Nearly silent | Premium - barely audible |
| 0.5-1.0 sones | Quiet refrigerator | Excellent for master baths |
| 1.0-2.0 sones | Normal conversation | Good for guest baths |
| 2.0-4.0 sones | TV at normal volume | Budget option |
We recommend 1.0 sone or less for master bathrooms.
Fan Features to Consider
- Fan + Light Combo - Built-in LED replaces ceiling fixture
- Fan + Heater - Adds warmth on cold mornings
- Humidity Sensor - Auto-activates when moisture detected
- Motion Sensor - Activates when someone enters
- Bluetooth Speaker - Built-in audio
ENERGY STAR Certification
ENERGY STAR fans are 65%+ more efficient than standard models with better performance and quieter operation.
Top Bathroom Fan Brands
- Broan-NuTone - Largest selection, every price point
- Panasonic - Ultra-quiet WhisperLine series
- Delta BreezSignature - DC motor, ENERGY STAR certified
Installation Tips
- Match fan to duct size (typically 4 inch)
- Always vent to outdoors - NEVER into attic
- Longer duct runs need higher CFM
Related Resources
- Broan-NuTone Brand Guide - Complete ventilation guide
- Glossary: CFM Explained
- Glossary: Sone Ratings
- TOTO Brand Guide - Bathroom fixtures