Ridge Vent Free Area Calculator
Here's a comprehensive table summarizing key information about ridge vent free area:
| Specification/Detail | Details |
|---|---|
| Net Free Area per linear foot | 18 inches (for ShingleVent II, etc.)1 |
| Recommended ventilation ratio | 1 sq ft of NFA required for every 150 sq ft of attic, or 1/300 under certain conditions1 |
| Typical sizes of ridge vents | 4 feet long covering 72 sq inches NFA6 |
| Importance of balancing intake and exhaust | Soffit NFA should equal or exceed ridge vent NFA2 |
| Minimum NFA for attic spaces | 15 sq inches NFA recommended per linear foot of ridge |
| Calculation formula | Attic square footage ÷ 150 or 300 = Net Free Ventilation Area6 |
| Ridge vent length calculation | (1/2 net free area x 144) ÷ 18 = feet of ridge vent needed1 |
| Soffit vent length calculation | (1/2 net free area x 144) ÷ 9 = feet of soffit vent needed1 |
| Ridge vent with baffle vs. without | Both require 20' of ridge vent for a 1,500 sq ft attic; baffle version recommended6 |
| Static roof vent requirement | 8 box vents (50 sq inches NFA each) for a 1,500 sq ft attic6 |
This table provides a quick reference for understanding ridge vent free area specifications, calculations, and requirements. It's important to note that local building codes and specific product specifications may vary, so always consult with a professional or refer to manufacturer guidelines for your particular situation.