Georgia Roof Guide

Is attic ventilation required, and how do you calculate how much is required?

Short answer. Yes. Georgia builds under the International Residential Code with state amendments, and Section R806 requires enclosed attics to be ventilated unless they are built as sealed, unvented attics. The required net free vent area is 1/150 of the attic floor area, or 1/300 when 40 to 50 percent of it is high exhaust and the rest is low intake.

Who requires it

Three parties care about your attic vents. The building code sets the minimum for new construction and permitted work. The shingle manufacturer usually ties its limited warranty to code compliant ventilation. And home inspectors flag missing or blocked vents during a sale. Georgia's current mandatory residential code is the 2024 International Residential Code with Georgia amendments, effective January 1, 2026, enforced by your city or county building department.

The calculation, step by step

  1. Measure the attic floor area. Example: a 40 by 50 foot attic is 2,000 square feet.
  2. Divide by 300 if the vents will be balanced high and low, or by 150 if they cannot be. 2,000 divided by 300 is about 6.7 square feet.
  3. Multiply by 144 to convert to square inches: about 960 square inches of net free area.
  4. Split it. Code allows 40 to 50 percent up high, so roughly 480 square inches of exhaust and 480 of intake. Many roofers aim for slightly more intake than exhaust.
  5. Divide each half by the net free area printed on the vent or its packaging to get feet of ridge vent or the number of soffit vents.

Details that trip people up

The high vents must sit within 3 feet of the ridge, measured vertically, to qualify for the 1/300 ratio. Vent openings need screening with openings between 1/16 and 1/4 inch. Insulation must not block the eave vents, and there must be at least 1 inch of air space under the deck at those vents. For a refresher on how the pieces fit, read roof ventilation basics, and see roofing permits in Georgia for how local enforcement works.

In depth

How much attic ventilation does a Georgia roof need?Attic ventilation for Georgia homes: intake and exhaust balance, the IRC R806 1/150 and 1/300 rules with workeDoes a hot Georgia attic shorten the life of your shingles?How hot Georgia attics and shingles get, what research says about ventilation and shingle life, and when radiaRidge vent or box vents: which is better, and can you use both?Ridge vents vs box vents, turbines and power fans for Georgia attics: how each works, why mixing exhaust types

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