Of total vent space needed.
Roof vent area calculation.
Multiply the length of the attic times the width in feet to find the attic area then divide by 150 to find the total square feet of vent space needed.
The federal housing authority fha and the urban development hud have established minimum requirements for attic ventilation.
In order to have a balanced ventilation system you need to have the right roof vent calculation.
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.
Enter square footage calculate or enter the square footage of the attic or area to be vented.
According to their requirements you should have 1 square.
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.
A normal metal pot vent produces only 50 squares inches of free net area.
Attics area can heat up to 165 degrees f or more 73 9 c.
Using the aggregate area of these simple shapes can yield a more accurate roof area to be used with the roofing material calculator.
Ft divided by 150 equals 10 sq.
Of net free area of intake needed at or near the soffit.
Width or area.
A roof s pitch is determined by how much it rises vertically for every foot it runs horizontally.
Of net free area of exhaust needed at or near the ridge.
Two square feet equals 288 square inches.
Length x width of attic in feet 150 total sq.
Roof ventilation calculator enter your attic area or length and width to determine your ventilation needs.
To accurately calculate the area of your roof you must first determine its slope or pitch.
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.
The calculations before indicated that we needed 2 square feet of ridge or upper roof ventilation.
A 50 x 30 attic would have a total area of 1 500 sq.
Use avp s roof vent calculator to determine the number and size of exhaust vents you will need.
Ridge static attic vents 384 00 minimum sq.
A 12 in 12 pitch is a.
Thus a moderate 6 in 12 roof pitch means that the roof rises 6 inches vertically for every 12 horizontal inches it runs.
For balanced ventilation an equal amount of intake vent area net free area should also be installed.
The area calculator can be used to calculate the area of a variety of simple shapes that together can comprise the area of the roof.
For the 1 150 attic ventilation requirement simply double the amount of exhaust and intake calculated.
