How Much Roof Vents Do I Need

This shortcut conveniently calculates the 2015 international residential building code minimum irc section r806 roof ventilation 1 which states in part 1 square foot of net free area for every 150 square feet of attic floor space with the attic defined as length x width floor of the attic.

How much roof vents do i need. If the slope of your roof is greater than 6 12 you will need more ventilation to reflect the extra volume of attic space. Near ridge of the roof. Rounding up you would need ten 10 750 vents. Federal housing authority recommends a minimum of at least 1 square foot of attic ventilation for every 300 square feet of attic floor space evenly split between intake and exhaust.

Asphalt roofing and nrca. How many vents will my house need. Because you always want your intake nfa to meet or exceed the amount of exhaust nfa we will take the amount of exhaust provided and divide by the nfa rating of the deck air. That said air resistance and interference such as vent grates reduces the area of true ventilation.

Calculate 20 per cent more for 7 12 to 10 12 pitches and 30 per cent more for a pitch that is 11 12 or greater. As a general rule your roof needs 1 square foot of vent area for every 150 square feet of attic space. They should be divided equally between inlet and outlet vents and they can be used in any combination that will work with your roof s design. Based on your 1100 sq.

To calculate the number of 750 vents needed divide 480 by 50 to get 9 6 vents. Of vent for every 300 sq. Building codes vary. And this guideline you ll need a minimum of.

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. Thus if your attic is 450 square feet you need roof vents equaling 3 square feet. 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. 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.

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.