Soffit ventilation system in a building having a horizontal soffit with a plurality of vents and a strip of mat of randomly oriented synthetic fibers covering the attic-facing side of the soffit. An alternative embodiment has a panel of air-impermeable material having upper and lower sections. The strip of mat of randomly oriented synthetic fibers is sandwiched between the lower section and the vertical side of the walls allowing the passage of air into the attic through an opening between the lower section and the upper section of the air-impermeable panel.