Now let s figure out how much ventilation space we need.
How much attic ventilation is required.
Federal housing authority recommends a minimum of at least 1 square foot of attic ventilation evenly split between intake and exhaust for every 300 square feet of attic floor space.
Enter square footage calculate or enter the square footage of the attic or area to be vented.
Let owens corning roofing help you calculate exactly how much ventilation you will need for a healthy and balanced attic with our 4 step ventilation calculator.
See how simple.
Is this too much ventilation.
Before we explore how to ventilate an attic space it is prudent to understand how much ventilation is needed.
Furthermore nrca also rec ommends the amount of ventila.
So how much ventilation should you have.
For large volume attics such as where roof slopes are greater than 8 12 designers also should consider increasing the amount of attic ventilation to account for the additional volume of attic space.
Proper attic ventilation consists of a balance between air intake at your eaves soffits or fascias and air exhaust at or near your roof ridge.
As an example in an attic that is 30 feet by 20 feet you would have 600 square feet of floor area.
Since manufacturers of static ventilation products rate their products in square inches of nfa it will be necessary to multiply that value by 144 to determine the square inches required.
According to the fha federal housing administration us for every 300 square feet of attic floor area you should have at minimum one square foot ventilation.
Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca.
Also should the vents to the crawl space be open in summer and closed in winter.
The following are the requirements taken directly from the irc.
Without exception you should talk to a professional to determine what your home requires.
The ventilation amount and opening size requirements can be found in section 806 roof ventilation of chapter 8 roof ceiling construction.
Of attic space 1 150 ventilation ratio measured at the attic floor level ceiling.
Divide that area by 150 to determine the square feet of attic ventilation needed.
So in our example we will divide the 1 500 square feet by 300.
Figure 1 soffit to ridge attic ventilation.
I have received several questions and comments since writing about attic ventilation.
Ok so now we know the square footage of the attic area to be ventilated.
Ventilation can be accomplished using various products and techniques.
1 500 square feet 300 5 square feet.
