The #1 attic mistake — mixing two exhaust types short-circuits the airflow

A ridge vent short-circuits any second exhaust (gable, box/turtle, or a powered fan), starving the soffits and leaving dead air low in the attic. Use ONE exhaust type + continuous soffit intake.

A wrong-versus-right comparison of attic exhaust. On the left, a ridge vent and gable louvers are both left open: the ridge pulls its air from the nearby high gable vent instead of the soffits, so the lower attic near the eaves becomes dead air and the deck is never flushed. On the right, a single exhaust — the ridge vent — is paired with continuous soffit intake and the gable is sealed, so air sweeps the entire underside of the deck. Use one exhaust type plus low intake; never combine a ridge vent with gable, box, or powered vents. — Source: GAF / Air Vent / Owens Corning installation guidance

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A wrong-versus-right comparison of attic exhaust. On the left, a ridge vent and gable louvers are both left open: the ridge pulls its air from the nearby high gable vent instead of the soffits, so the lower attic near the eaves becomes dead air and the deck is never flushed. On the right, a single exhaust — the ridge vent — is paired with continuous soffit intake and the gable is sealed, so air sweeps the entire underside of the deck. Use one exhaust type plus low intake; never combine a ridge vent with gable, box, or powered vents.

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    <img src="https://remodelcalculators.com/api/figure-embed/attic-ventilation-mixing-mistake" alt="A wrong-versus-right comparison of attic exhaust. On the left, a ridge vent and gable louvers are both left open: the ridge pulls its air from the nearby high gable vent instead of the soffits, so the lower attic near the eaves becomes dead air and the deck is never flushed. On the right, a single exhaust — the ridge vent — is paired with continuous soffit intake and the gable is sealed, so air sweeps the entire underside of the deck. Use one exhaust type plus low intake; never combine a ridge vent with gable, box, or powered vents." width="800" height="470" style="width:100%;height:auto;border:0" loading="lazy">
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