Air Vent 81237 Aluminum Reversible Louver, 18" x 24", WhiteWall louvers are installed in the gable end of the attic. The higher they are placed, the more effective they become as exhaust vents. Wall louvers are not preferred for ventilating an attic, because they provide limited airflow under the roof deck, resulting in "hot spots". Can be used where ridge vents are impractical, or where the homeowner doesn't want roof vents. White Reversible 118. 8 sqin net free area Riveted construction Improves air flow