Exhaust Louver Size Calculator

Louver Area Formula:

\[ \text{Louver area (sq ft)} = \frac{\text{Exhaust rate (CFM)}}{\text{Max velocity (fpm)}} \]

Louver area (sq ft):

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1. What is the Exhaust Louver Size Calculation?

The exhaust louver size calculation determines the required area of a louver based on the exhaust airflow rate and maximum desired air velocity through the louver. Proper sizing ensures efficient airflow while maintaining acceptable pressure drops.

2. How Does the Calculator Work?

The calculator uses the following equation:

\[ \text{Louver area (sq ft)} = \frac{\text{Exhaust rate (CFM)}}{\text{Max velocity (fpm)}} \]

Where:

Exhaust rate (CFM) — Cubic feet per minute of air being exhausted
Max velocity (fpm) — Maximum desired air velocity through the louver (feet per minute)
Louver area (sq ft) — Required free area of the louver in square feet

Explanation: The equation calculates the minimum free area needed to maintain air velocity below the specified maximum.

3. Importance of Proper Louver Sizing

Details: Correct louver sizing is crucial for maintaining proper airflow rates, minimizing pressure drops, reducing noise, and preventing water intrusion in exhaust systems.

4. Using the Calculator

Tips: Enter the exhaust rate in CFM and maximum desired velocity in fpm. Typical maximum velocities range from 500 fpm for gravity ventilators to 2000 fpm for storm-resistant louvers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical maximum velocity for exhaust louvers?
A: Standard louvers typically use 500-800 fpm, while storm-resistant louvers may allow up to 2000 fpm.

Q2: Should I account for louver free area percentage?
A: Yes, this calculation gives the required free area. The actual louver size will be larger based on the manufacturer's free area percentage.

Q3: How does louver type affect the calculation?
A: Different louver types have different pressure drop characteristics at various velocities. Consult manufacturer data for specific applications.

Q4: What about rain defense requirements?
A: For applications requiring rain defense, additional factors like blade design and orientation must be considered beyond just velocity.

Q5: How does altitude affect the calculation?
A: At higher altitudes, air density changes may require adjustments to the CFM values for equivalent mass flow rates.