Calculate or enter the square footage of the attic or area to be vented.
Square footage of vent for roof.
Nfa is the unobstructed area through which air can pass through a vent usually measured in square inches.
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.
As a general rule your roof needs 1 square foot of vent area for every 150 square feet of attic space.
Ridge static attic vents 384 00 minimum sq.
Ventsure 4 foot strip heat moisture ridge vent.
27 lineal feet required.
Thus if your attic is 450 square feet you need roof vents equaling 3 square feet.
For the 1 150 attic ventilation requirement simply double the amount of exhaust and intake calculated.
Of net free area of exhaust needed at or near the ridge.
Choose one of the following products to meet the recommended exhaust nfva of 528 square inches.
Ventilation manufacturers assign an nfa value to the non motorized vents they make.
Pick out your soffit vent size and determine the square footage of the vent.
Vent roofs with steeples towers or cupolas can be found in different buildings from barns to cathedrals.
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.
One square foot equals 144 square inches so the standard 16 inch by 8 inch soffit vent is 0 89 square feet.
The building codes and building science for.
Of net free area of intake needed at or near the soffit.
The calculator cannot account for complex shapes based on a measurement of square footage alone.
For example if you use 16 inch by 8 inch soffit vents each vent is 128 square inches.
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.
6 measure the radius of round vents or take half the diameter of the.
The idea of roof vents existed for hundreds of years with natural vents employed in chinese buildings during the tang dynasty natural ventilation ducts in the buddhist monks caves and wind catchers incorporated in arabian architecture.
For example a 6 by 12 inch soffit vent has 72 square inches which when divided by 144 results in a 0 5 square foot opening.
In cases where a roof has a complex shape such as in the image to the right measuring the dimensions and areas of each part of the roof to calculate total area will result in a more accurate measurement of area.
Attic square footage 2 square inches of exhaust and square inches of intake net free area nfa needed.
