I have gable roof with a 90’ foot ridge. I plan on using a Ridge vent (Cobra Snow Country) to help ventilate my attic. According to 1/300 rule (2700 sq. ft. of attic), I calculated that I need 648 Sq. inches of NFVA exhaust ventilation and 648 sq. inches of NFVA intake. The ridge vent I plan on using has specs of 16 sq. inches per lineal foot NFVA that comes out to (16x90ft) 1440 sq. inches of NFVA. Is this too much or can I balance this out with more under eave vents? I have the feeling that my 1960’s home doesn’t have the proper amount ventilation passing through the eaves. What should I do? Does anybody have a better recommendation for ridge vent other than Cobra? Are my NFVA calculations correct?