Calculating Ridge and Soffit Vent Size

This video describes calculating ridge vent and soffit vent size.

1/300 and 1/150 are the recommended guidelines. 1/150 is the most recommended. That means 1sq.ft of vent area per 150sq.ft of attic area.

LengthxWidth=Area of Attic

Attic Area / 150 = Vent area

Ridge Length x Net Free Area of Ridge vent = Vented Area of Ridge

Vent area of the 2 soffits combined should equal the vented area of the ridge

Soffit vent size

Vented area / number of soffit vents = size of each soffit vent

Soffit vent number

Vented area / size of soffit vents = number of soffit vents