How Much Roof Vents Do I Need

How many vents will my house need.

How much roof vents do i need.

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. And this guideline you ll need a minimum of. In other words the entire vent opening doesn t count as vented space. In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq.

Thus if your attic is 450 square feet you need roof vents equaling 3 square feet. To calculate the number of 750 vents needed divide 480 by 50 to get 9 6 vents. 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. 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.

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. Of vent for every 300 sq. Rounding up you would need ten 10 750 vents. That said air resistance and interference such as vent grates reduces the area of true ventilation.

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. Generally speaking you need a ratio of 1 300 where for every 300 square feet of ceiling space you need 1 square foot of attic ventilation. 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. If the slope of your roof is greater than 6 12 you will need more ventilation to reflect the extra volume of attic space.

Asphalt roofing and nrca. Based on your 1100 sq. Near ridge of the roof. 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 a general rule your roof needs 1 square foot of vent area for every 150 square feet of attic space.