1. What is CFM in Exhaust Fans?

CFM (Cubic Feet per Minute) measures the airflow volume an exhaust fan can move. It's a crucial specification for determining a fan's capacity to ventilate a space effectively.

2. How Does the Calculator Work?

The calculator uses the CFM formula:

Where:

• \( RPM \) — Fan revolutions per minute
• \( Blade\ Area \) — Total area of fan blades in square feet
• \( Efficiency \) — Fan efficiency as a fraction (0-1)

Explanation: The equation calculates the volume of air moved by multiplying the fan's speed by the area it covers and its efficiency factor.

3. Importance of CFM Calculation

Details: Proper CFM calculation ensures adequate ventilation for spaces, prevents moisture buildup, removes odors, and maintains air quality in residential, commercial, and industrial settings.

4. Using the Calculator

Tips: Enter fan RPM (typically 1000-3000 for residential fans), blade area in square feet (calculate as π × radius² for circular fans), and efficiency (typically 0.7-0.9 for good quality fans).

5. Frequently Asked Questions (FAQ)

Q1: What's a good CFM for a bathroom exhaust fan?
A: Generally 50-100 CFM for standard bathrooms (1 CFM per square foot), higher for larger spaces or steam showers.

Q2: How do I measure blade area?
A: For circular fans, measure blade diameter, divide by 2 for radius, then calculate area as π × radius² (convert to square feet).

Q3: What affects fan efficiency?
A: Blade design, motor quality, housing shape, and cleanliness. Well-maintained fans operate at higher efficiency.

Q4: Can I use this for axial and centrifugal fans?
A: This formula works best for axial fans. Centrifugal fans may require different calculations due to their airflow patterns.

Q5: How often should I recalculate CFM needs?
A: Whenever you change room size, add appliances that produce heat/moisture, or if you notice inadequate ventilation.