Let owens corning roofing help you calculate exactly how much ventilation you will need for a healthy and balanced attic with our 4 step ventilation calculator.
How many roof vents do i need for my house.
Rafter vents or insulation baffles install in any rafter space to create narrow gaps that direct fresh air from the soffit vents to the peak of the roof.
Ideally there should also be plenty of soffit intake space their calculations recommend 336 net square inches of open soffit ventilation to supply 700 cfm.
Use the calculator below to find out how many exhaust and intake vents you will need on your house.
If there is no vapor barrier double it to one square foot of nfa for every 150 square feet of attic floor space half for intake half for exhaust.
That said air resistance and interference such as vent grates reduces the area of true ventilation.
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.
Thus if your attic is 450 square feet you need roof vents equaling 3 square feet.
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.
Hvi recommends a ratio of 60 to 40 for soffit ventilation to gable or ridge ventilation.
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.
Choose one of the following products to meet the recommended exhaust nfva of 528 square inches.
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.
Choosing round soffit vents for.
Always have a balanced ventilation system.
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.
If your attic floor has a vapor barrier you will need one square foot of nfa per every 300 square feet of attic floor area half of that will be intake half for exhaust.
In no case should the amount of exhaust ventilation exceed the amount of intake ventilation.
These specialty vents do not affect the.
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.
