How to Determine the Number of Roof Vents Required

Keeping your attic ventilated properly is important for several reasons. Without proper ventilation, your attic can become extremely hot, which can heat up your home, raising energy costs because you need to run the air conditioner more often. The buildup of excessive heat in the attic can also play havoc on your roof, causing shingles to curl up and exposing the roof to leaks. You can calculate the number of roof vents your attic needs to prevent these problems. A general rule of thumb is to provide 1 square foot of ventilation for 150 square feet of floor space.

Things You'll Need

• Tape measure

Show More

Instructions

1. • 1

     Measure the length and width of the attic floor to determine the square footage. In this example, we'll use an attic that measures 20 feet wide by 30 feet long.

   • 2

     Multiply 20 feet by 30 feet and you get 600 square feet of floor space.

   • 3

     Divide the square footage of the floor by 150. Use 150 because you want to use one vent for every 150 feet of floor space; 600 divided by 150 is 4, so you want to install four vents in the roof to provide proper ventilation.