How To Figure Required Air Vent For A Roof

Adding under roof ventilation is usually a great idea but if the relative sizes of the intake and outlet vents are not proper the building will suffer increased heat loss and thus an unnecessarily high home heating bill.

How to figure required air vent for a roof. 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. Multiple these two. If you have 3 000 square feet of attic space this equates to 20 square feet of ventilation needed. And this guideline you ll need a minimum of.

The federal housing administration recommends 1 square foot of attic. Divide the square footage by 150 to calculate the area of ventilation needed since you need 1 square foot of vent space for each 150 square feet of attic space. In our case the required 4 vents for the 1200 sq ft house multiply the 144 cubic inches by 4 576 cubic 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.

Jones takes this measurement and divides it by 150 for a total of 7 36 square feet of ventilation space that is needed. 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. Jones must now take this required ventilation space and compare it against the total ventilation that he currently has for his attic space. Measure the length and width of the attic space using a tape measure.

How many vents will my house need. You can calculate attic ventilation requirements by determining the square footage of your attic floor its width times its length and compare that to the total required net free area nfa. How to determine the number of attic vents. Divide the attic s square footage by 150.

Attic ventilation soffit intake to ridge outlet air flow or square inches ratio. This calculator gives you the required attic ventilation requirement. This ratio is required for modern insulated homes. Based on your 1100 sq.

Near ridge of the roof. 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 your roof is 1200 sq ft soffit floor space you will need 4 sq feet of roof ventilation. Calculate the square footage of your attic.

1 cubic foot is 12 x 12 144 cubic inches. Next multiply the 4 square feet into cubic inches.