Attic Vents Per Square Foot

We recommend a minimum of 12.7 nfa per foot.

Attic vents per square foot.

There are two important pieces of information required to calculate the adequate number of vents. The general rule of thumb on the amount of total attic vent space needed is to have at least one square foot of vent space for every 150 square feet of attic area. So, if your attic is 450 square feet, you will need 3 square feet of vent space, evened out throughout the entire space and divided equally between inlet and outlet vents.

Say the contractor is standing in front of a house that has an attic with 2,200 square feet. Attic square footage ÷ 4 = square inches of exhaust and square inches of intake net free area needed. Most local building codes require compliance with either the 1/150 method or the 1/300 method exception (refer to local.

This vent area should be divided equally between the soffit areas on both sides of the roof. 2,200 ÷ 2 = 1,100 square inches of exhaust net free area needed According to the national roofing contractors association (nrca), a power vent with an airflow rate of 1.0 cubic foot per minute per square foot of attic space measured at the attic floor is generally considered to be equivalent to a 1:150 ventilation ratio.

Determine the net free ventilating area the attic vents you plan to. To calculate the total minimum soffit vent intake area in square inches, divide the cfm of the pav by 300 and multiply the result by 144. The general rule of thumb in these situations is of roughly one vent per every 300 square feet of attic area if the attic has a vapor barrier.

I am pretty sure you are wondering how i calculated this size. The 10 square feet x 144 square inches per square foot =. Federal housing authority recommends a minimum of 1 square foot of attic ventilation (evenly split between intake and exhaust) for every 300 square feet of attic floor space.

Example building 1,000 divided by 300 = 3.33 total square feet. The net free area (nfa) rating indicates the amount of space each roof vent covers. Attic square feet x 0.7 = cfm capacity for example, using the same dimensions as the previous example: