1. What is NFA (Net Free Area)?

Net Free Area (NFA) is the unobstructed area through which air can pass through a vent. For roof ventilation, it's a critical measurement that determines how much air can flow in and out of your attic space.

2. How Does the Calculator Work?

The calculator uses the standard formula:

Where:

• \( NFA \) — Net Free Area in square feet
• \( Attic\ Area \) — Total attic floor area in square feet

Explanation: This formula follows the standard building code requirement of 1 square foot of NFA for every 150 square feet of attic space.

3. Importance of Proper Roof Ventilation

Details: Proper roof ventilation prevents moisture buildup, reduces cooling costs in summer, prevents ice dams in winter, and extends the life of your roofing materials.

4. Using the Calculator

Tips: Measure your attic's floor area in square feet and enter it in the calculator. The result will show the required Net Free Area for proper ventilation.

5. Frequently Asked Questions (FAQ)

Q1: Why is the ratio 1:150?
A: This is the standard ratio recommended by most building codes for balanced attic ventilation systems.

Q2: Should intake and exhaust vents be equal?
A: Ideally, yes. For optimal performance, the net free area of intake vents should equal the net free area of exhaust vents.

Q3: What types of vents contribute to NFA?
A: Ridge vents, soffit vents, gable vents, roof louvers, and turbine vents all contribute to the total NFA.

Q4: Are there different requirements for different climates?
A: In some extreme climates, local building codes may require different ratios. Always check with local regulations.

Q5: How do I measure my attic area?
A: Measure the length and width of your attic floor space and multiply them to get the total square footage.