2022-04-13 00:00:00 Roof Ventilator - Roof Attic Space Ventilation Calculator Our application uses two inputs (one required): Attic Space Net Free Area and Intake Ventilation Net Free Area. You will have to calculate those two inputs on your own. Once the calculations are complete, enter the inputs into the application and find instant pertinent information calculated by our application that helps design your ventilation system to be within code limits and provide ventilation balance by providing instantaneous notifications of balance between intake net free area and exhaust. Roof attic vent calculator Provides: