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.

How much roof vents do i need. And this guideline you ll need a minimum of. If the slope of your roof is greater than 6 12 you will need more ventilation to reflect the extra volume of attic space. Of vent for every 300 sq. Based on your 1100 sq.

As a general rule your roof needs 1 square foot of vent area for every 150 square feet of attic space. 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. 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.

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. 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. 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.

Rounding up you would need ten 10 750 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. 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. How many vents will my house 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. 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. Building codes vary.

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.