Why Adding Insulation Did Not Fix Your Milwaukie, Oregon Attic: Roof Ventilation Is a Balanced System

A ventilated roof works by convection. Cool outside air enters through intake vents in the soffit at the eave, travels up the underside of the roof deck through channels between the rafters, and exits through exhaust vents at the ridge. Intake and exhaust have to be roughly balanced in free area. If either side is undersized or blocked, air stops moving and the system stops working, regardless of how much vent hardware is on the roof.