How much attic ventilation do I need?
Use the 1/300 rule. This means that for every 300 sq/ft of attic space you will need 1 sq/ft of ventilation. Convert the total needed to square inches and use half of that amount for the soffit and the other half for the ridge. Vents are labeled in square inches. Example 2,000 sq/ft attic- 2,000/300= 6.67. Convert to square inches 6.67 x 144= 960 sq/inches. 960 x 50%= 480 sq/inches for the soffit and 480 sq/inches for the ridge.