Calculating Your Ventilation Needs

Note: Calculations are based on 1 square foot of Net Free Area
for every 150 square feet of residential attic floor space.


Numbers are based on average roof pitch between 4/12 and 10/12

Enter the width and length of your home, including overhang (in feet):
Your width measurement is parallel to the ridge
Your length is the measurement perpendicular to the ridge
Total Area
(Sq Ft)
Minimum NFA needed
(Sq Inches)

*Calculations are based on a standard “A” frame roof with an average roof pitch. *These are minimum requirements for proper venting, actual vents should extend to the ends of the roof when possible with a maximum rafter length of twenty-four(24) feet per side. * For commercial use, please call DCI Products with detailed information. Commercial applications include rafters that have a length greater than 24 feet per side.


SmartRidge II (EXHAUST) – 18 NFA Ridge Vents

Pieces of SmartRidge I or SmartRidge II needed for exhaust or ft.
SmartVent (INTAKE) – 9 NFA Continuous Soffit Intake Vents
Pieces of SmartVent or FasciaVent needed for intake or ft.

DCI Products Inc. 1-800-622-4455

SmartBaffle for Superior Ventilation