What Size Roof Turbine Ventilator Is Best for Your Roof?

A turbine vent on top of a roof.
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Using a roof turbine ventilator to increase the flow of air in your attic is a great idea. A roof turbine ventilator requires only the wind to work. These vents aren't one-size-fits-all, though. They come in a variety of styles and sizes to suit different situations.

Making sure you have the proper size vent is key in increasing airflow in your attic. If you install a vent that is too small or too big, you may just be throwing your money out the window—or roof. The tips below will help you decide which size of the turbine vent is best for you.

City Codes

The first thing to do is to go to your city building department and get the latest codes in regard to venting. Most policies in place require about one foot of vent area for every one hundred fifty feet of attic space.

This is one of the most important steps. If you install a vent that isn't up to code, you could end up having to take it down, wasting money and time. Also, this will give you general guidelines to follow as you complete your project.


There is a mathematical equation to determine how much venting you will need. First, find out the square footage of your attic and sketch it onto the graph paper. Now, take the square footage number and multiply it by 144. This will give you square inches, instead of square feet. Take this number and divide it by three hundred. The quotient is the amount of ventilation you will need for your attic.