How do I calculate the free area of a louver to ensure I meet the engineer's specs

Plain-English answer

The structural metal blades of an intake louver block a large percentage of the open wall frame space. * Look up the manufacturer's submittal data sheet to find the designated Percent Free Area rating (typically ranging from 45% to 60%).

\text{True Free Area Space} = \text{Total Rough Opening Area (Width} \times \text{Height)} \times \text{Percent Free Area Rating}

If your calculation drops below the absolute net square footage required by the engineer, the system fan will starve for air and whistle loudly.

Field checklist

• Stop and verify the approved detail, manufacturer instructions, foreman direction, and project specs before touching it.
• The structural metal blades of an intake louver block a large percentage of the open wall frame space. * Look up the manufacturer's submittal data sheet to find the designated Percent...
• \text{True Free Area Space} = \text{Total Rough Opening Area (Width} \times \text{Height)} \times \text{Percent Free Area Rating}
• If your calculation drops below the absolute net square footage required by the engineer, the system fan will starve for air and whistle loudly.

Ask Foreman

Verify before acting

Use this as training guidance. The foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements always control the final answer.

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