Renovation: Completely Revised and Updated Proper attic ventilation is critical for a healthy home. Determining what you need is simple. All you need is the size of your house and a calculator. Attic ventilation should equal approximately 1 square foot of vent area for every 300 square feet of attic, so figure out roughly how many square feet the footprint of your attic is, and then divide by 300. To ensure effective air movement throughout the attic, the total vent area should be split approximately evenly between high and low vents, so now divide that number by two to get a rough idea of how much low ventilation and how much high ventilation your home needs.

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