1. What is a Roof Vent Calculator?

Definition: This calculator determines the required net free vent area for a roof attic based on the attic floor area.

Purpose: It helps homeowners and contractors ensure proper attic ventilation according to building codes.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( V \) — Required vent area (square feet)
• \( A \) — Attic floor area (square feet)

Explanation: Building codes typically require 1 square foot of net free vent area for every 150 square feet of attic floor space.

3. Importance of Proper Attic Ventilation

Details: Adequate ventilation prevents moisture buildup, reduces cooling costs, extends roof life, and prevents ice dams in cold climates.

4. Using the Calculator

Tips: Enter the total attic floor area in square feet. The value must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is the ratio 1:150?
A: This is the minimum requirement in most building codes for balanced attic ventilation.

Q2: Should vents be equally distributed?
A: Yes, ideally 50% intake (soffit) vents and 50% exhaust (ridge or roof) vents.

Q3: What if my attic has a vapor barrier?
A: Some codes allow 1:300 ratio if a vapor barrier is properly installed.

Q4: How do I measure attic area?
A: Multiply the length by width of your attic floor space (same as your house footprint if standard construction).

Q5: Does this include all vent types?
A: The calculation is for net free area - check manufacturer specs as different vent types have different net free areas.