4 steps to calculate vent area

摘要

If an attic measures 900 sq. ft., code requires that there be a minimum of 3 sq. ft. of ventilation area (1 sq. ft. for every 300 sq. ft. of attic-floor area), with between 40% (1.2 sq. ft.) and 50% (1.5 sq. ft.) of ventilation area at the ridge and the remainder at the soffits. If there is no ridge vent, this same attic would require 6 sq. ft. of ventilation area at the soffits. Here's how to calculate the amount of venting you need when using a product with a theoretical rating of 9 NFVA per ft.