# How is soffit ventilation calculated?

## How is soffit ventilation calculated?

Start by measuring the width and length of your attic and then multiply them by one another. Next, divide the total square footage by 150 (remember, 1 foot of vent space/150 sq ft). The final number will be the total square footage of the vent space you need for your attic.

Are soffit vents required by code?

What does the code require? If you plan to install insulation on your attic floor, then most building codes require that the attic be vented. If a roof has only soffit vents and no ridge vents, most codes require 1 square foot of net free ventilation area for every 150 square feet of attic floor area.

How do I calculate roof ventilation?

2 of the IRC says that in most cases a 1:150 ratio (NFA of vent to total attic square footage) should be used to determine the minimum size requirements for the vent. So for an attic that’s 1,000 square feet, you would divide 1,000 by 150 to calculate that 6.6 square feet NFA of ventilation would be required.

### What is soffit ventilation?

Soffit vents are roof ventilation devices installed underneath the eaves of a roof that extend past the warm wall line. When properly combined with other roof ventilation devices, soffit vents allow fresh air to enter into an attic creating air flow.

How do you calculate the number of soffit vents?

Determine the number of soffit vents needed: Divide the total soffit vent area by the area of each vent. [soffit vent area in sq. ft. ÷ individual vent area in sq. ft. = number of vents needed]. Example: 5 sq. ft. soffit vent area divided by 0.5 sq. ft. vent area equals 10 soffit vents needed.

What is the purpose of the soffit calculator?

This soffit system calculator, and the information gleaned from the same, is designed for information purposes only and not intended to constitute professional advice, create a contract, or be intended to serve as any sort of a guarantee.

#### How to calculate attic vent net free area?

For optimum performance, the attic ventilation system must be balanced with intake and exhaust vents. This is a simple calculation: just divide the answer from Step 2 by 2. Calculation: 6.6 ÷ 2 = 3.3 sq. ft. of intake net free area and 3.3 sq. ft. of exhaust net free area Section 3: Determining Ventilation Requirements13

How to calculate the size of a ventilation system?

Always have a balanced ventilation system. In no case should the amount of exhaust ventilation exceed the amount of intake ventilation. 1. Measure Measure the length and width of the attic floor space to be ventilated.