6 measure the radius of round vents or take half the diameter of the.
Square footage of vent for roof.
As a general rule your roof needs 1 square foot of vent area for every 150 square feet of attic space.
Of net free area of exhaust needed at or near the ridge.
For example if you use 16 inch by 8 inch soffit vents each vent is 128 square inches.
Calculate or enter the square footage of the attic or area to be vented.
Vent roofs with steeples towers or cupolas can be found in different buildings from barns to cathedrals.
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.
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.
There are also gable and roof fans which actively pull the hot air out of the attic.
Pick out your soffit vent size and determine the square footage of the vent.
Ridge static attic vents 384 00 minimum sq.
Ventsure 4 foot strip heat moisture ridge vent.
Nfa is the unobstructed area through which air can pass through a vent usually measured in square inches.
Of net free area of intake needed at or near the soffit.
Divide this by 144 to calculate how many square feet each vent is.
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.
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.
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.
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.
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.
27 lineal feet required.
Choose one of the following products to meet the recommended exhaust nfva of 528 square inches.
One square foot equals 144 square inches so the standard 16 inch by 8 inch soffit vent is 0 89 square feet.
Attic square footage 2 square inches of exhaust and square inches of intake net free area nfa needed.
Ventilation manufacturers assign an nfa value to the non motorized vents they make.
The building codes and building science for.
