Why improperly proportioned intake vs exhaust air creates negative pressure that sucks conditioned living space air into the Proper attic ventilation depends on maintaining a balanced flow of air between intake and exhaust openings. When these components are improperly proportioned, the ventilation system can create pressure imbalances that affect both the attic and the conditioned living space below.

Why Intake-to-Exhaust Balance Matters

Improperly proportioned intake versus exhaust air creates negative pressure that can draw conditioned living-space air into the attic through ceiling penetrations, recessed lights, duct openings, electrical fixtures, and other small gaps.

Instead of pulling replacement air from the exterior through the soffits, an attic with insufficient intake capacity may begin drawing air from the conditioned portion of the home. This can increase energy loss and place additional demand on the heating and cooling system.

A properly designed ventilation system should allow outdoor air to enter through dedicated intake vents while warm, humid attic air exits through the exhaust system.