Attic ventilation is one of the least visible parts of a roof and one of the most important. A roof with the right shingles installed perfectly can still wear out early if the attic under it cannot breathe.
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How it works
Good ventilation moves air through the attic continuously. Cooler outside air comes in low, at the eaves, and hot, damp air leaves high, near the ridge. That flow does two things:
Types of vents
Intake vents let air in:
Exhaust vents let air out:
The rule of thumb
Building codes commonly call for about 1 square foot of net free vent area for every 150 square feet of attic floor, or 1 per 300 when the ventilation is balanced between high and low. Balance matters: intake should roughly equal exhaust. An attic with plenty of exhaust but blocked soffits pulls air from the wrong places, including the living space.
Common mistakes
Warning signs
Ventilation and your warranty
Several major shingle manufacturers require proper attic ventilation as a condition of their warranty. If a warranty claim comes up, an unventilated attic can be the reason it gets denied.
When to fix it
The best time is during a roof replacement, when ridge vents can be cut in and intake problems corrected without extra tear-off. We check ventilation on every inspection and correct it on every replacement. Call (855) 741-ROOF to have your attic looked at.