ClarityHow to use this tool
- Enter attic floor area, floor-to-vent area ratio, intake share.
- Select Calculate to view the result.
- Check the method and assumptions below before using the result.
The method, explained
Total net free vent area = attic floor area/ratio. Split this total by the selected intake percentage.
Using attic floor area = 100 m², floor-to-vent area ratio = 300, intake share = 50 %, the result is 0.333333333 m². Change these example inputs to match your task; use the method above to check each step.
Understanding your result
The example ratio is editable, not a code determination. Use net free area after screens and louvers and verify local requirements.
What to keep in mind
The example ratio is editable, not a code determination. Use net free area after screens and louvers and verify local requirements. A material-quantity estimate, not a structural design or building-code check. Confirm site measurements, supplier coverage and waste before ordering.
Common questions
How do I use this attic ventilation area calculator?
Calculate net free ventilation area from attic floor area and a user-specified ratio. Enter attic floor area in m², floor-to-vent area ratio, intake share in %. The starting example is editable; use values for the same system or project.
Which assumptions affect this result?
The example ratio is editable, not a code determination. Use net free area after screens and louvers and verify local requirements.
Methodology maintained by ClarityKit. How these tools are built and checked.