When installed in accordance with manufacturer's recommendations, Air Vent products comply with the net free area requirements of nationally recognized model codes, including those written by BOCA, SBCCI and ICBO.

Here's an overview of the specifications for Air Vent's complete line of intake ridge ventilation products.

THE SIMPLE MATHEMATICS OF A BALANCED RIDGE VENTILATION SYSTEM

• According to most building codes, you need 1 square foot of ventilation for every 150 square feet of attic floor space.
• For new home construction that includes a vapor retarder, the minimum is 1 square foot of ventilation for every 300 square feet of attic floor space.
• If your vents are split between ridge vents and intake vents, the minimum requirement is also 1 square foot of ventilation for every 300 square feet of attic floor space.

To determine how many feet of net free area you need, use this formula:

Ridge Vent/Intake Vent Calculator for Standard Gable Attic

To use this calculator, first find the total square footage of the attic floor area. Round your calculations up to the next highest number (see Ventilations Requirements).

Then look across to the number under the Minimum Length of Ridge column. That tells you the total linear feet of ridge vent required using the 1/300 minimum code requirements. Note: because today's tighter homes require more airflow, the 1/150 ratio is also included.

To balance your ridge vent system, find the length of the ridge and follow the column to the right for required intake vents (see Balancing Your Ridge Vent System).

Ventilation Requirements

Note: Calculations are based on ShingleVent II and Multi-Pitch FilterVent which provide 18" of net free area per linear foot.

Balancing Your Ridge Vent System