How Much Roof Vents Do I Need

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.

How much roof vents do i need.

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. 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. 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.

Of vent for every 300 sq. 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. In other words the entire vent opening doesn t count as vented space.

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

In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq. Building codes vary. Based on your 1100 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.

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. Near ridge of the roof. 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.

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.