How Much Roof Vents Do I Need

To calculate the number of 750 vents needed divide 480 by 50 to get 9 6 vents.

How much roof vents do i 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. As a general rule your roof needs 1 square foot of vent area for every 150 square feet 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. 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.

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. Asphalt roofing and nrca. 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. And this guideline you ll need a minimum of.

Thus if your attic is 450 square feet you need roof vents equaling 3 square feet. 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. Building codes vary. If the slope of your roof is greater than 6 12 you will need more ventilation to reflect the extra volume of attic space.

How many vents will my house need. In other words the entire vent opening doesn t count as vented space. Of vent for every 300 sq. 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.

In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq. That said air resistance and interference such as vent grates reduces the area of true ventilation. Rounding up you would need ten 10 750 vents. 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.

Near ridge of the roof.