Home > Blog

How to Calculate Proper Home Attic Ventilation

Attic ventilation. It’s a topic that is not commonly discussed and yet, when it comes to providing your house with the maintenance that it needs, it’s very important. Not only does a well-ventilated attic ultimately help to reduce energy costs, but it also helps to keep the humidity levels down too. That’s a good thing because it ultimately prevents you from having to worry as much about leaking roofs, water damage and the formation of ice dams in your attic during the winter season.

However, in order to make sure that your attic is receiving the proper amount of ventilation that it needs, it’s important that you do a bit of calculating. Although it might seem a bit complex at first, if you follow these five steps, you’ll be well on your way to having a well-ventilated attic in just a matter of a couple of hours.

Figure out the square footage of your attic space. The first thing that you need to do is find out what the square footage of your attic is. Say for example that your attic is 50X40 feet. If that’s the case, then when you multiply them together, that will equate to 2,000 square feet.

Divide your number by 150. Once you know what the square footage is, the next thing that you should do is divide that number by 150. That number will give you what is known as the Total Net Free Ventilating Area. What this actually represents is the fact that there should be proper ventilation that is provided in your attic for every 150 square feet of space. So, in the case of a 2,000 square foot home, the formula would be this: 2000 ÷ 150 = 13.33. This number represents the total square footage of attic venting that your house is going to need.

Then divide the square feet by square inches. The next step that you need to take is to convert the square foot into inches. You do this by multiplying the total square footage of attic venting (13.33) by the number of square inches (12) that are in a square foot (12). With the numbers that we’ve been using, it would be 13.33 × 144 = 1919.52. If you round this up to 1920, that is approximately the square inches of venting that is required. This is good to know being that vents are typically measured in inches.

Calculate your intake and exhaust venting percentage. In order to figure out both your intake and exhaust venting percentage, your intake needs to be based on 60 percent and your exhaust needs to be based on 40 percent. This provides a 60/40 split. So, 1920 × .60 = 1152 shows you the inches needed for your intake vents and 1920 × .40 = 768 shows you what you need for the inches for your exhaust vents.

Choose the right vents for ventilation. Whether you were trying to figure out how to choose the right size tankless water heater, how to select some good fans for the rooms of your house or how to choose the best vents for your attic, it’s always a good idea to speak with a professional. As it relates to your attic vents specifically, a customer service agent at your local home improvement store should be able to assist you.

More to Read: