How to calculate ventilation using Duraflo Vents


Duraflo we know ventilation.

How much ventilation will you need for your space?

According to the National Building Code, a minimum of 1 sq. ft. of ventilation for every 300 sq. ft. of attic space is required. On low slope applications, double the ventilation is needed: 1 sq. ft. for every 150 sq. ft. of attic space. This calculation includes both the intake and exhaust. Most vent manufacturers recommend a balanced system with half the air coming in through the soffits and half going out through the exhaust.

So how do you know how to get the perfect number of vents to have a home breathing right? Well, sometimes less is more, which is why we don’t recommend putting 11 roof vents on a single gable-style home… And we don’t recommend mixing your ventilation. Choosing a single type of ventilation makes it much easier to ensure that your soffits are breathing air into your home, and your roof vents are breathing this air out.

Here’s our four step process:

  1. Calculate the square footage of your attic space. To do this, measure the length and width of your home.
  • For example: Width: 50 ft, Length: 40 ft (50ft x 40 ft = 2000 sq. ft.)

  1. According to the National Building Code, you need 1 sq. ft. of ventilation for every 300 sq. ft. of attic space. Divide your square footage by 300 sq. ft. to find out how many vents you will need, then round up to make sure you’re getting enough ventilation.
  • For example: 2000 sq. ft./300 sq. ft.= 6.67

  1. Convert square feet of NFA to square inches by multiply square feet of NFA by 144 (6.67 sq. ft. x 144 = 960.48 square inches of NFA needed)

  1. To ensure your roof vents are drawing from your soffits, and not your other roof vents, we recommend that 50 percent of your ventilation should be covered by your soffits, and 50 percent should be covered by your roof vents (50/50). This means you should divide the number of vents by two. We need 10 vents for our 2000 sq. ft. application if you are choosing a 50 square inch roof vent.


It’s important to note that if your roof pitch is under 4/12, you will have to double the amount of ventilation that you need.

Duraflo Recommended Vents:

– An Article by Duraflo

Visit Duraflo’s website to use their Ventilation Calculator Tool at
Duraflo offers a range of ventilation in different sizes, styles and heights. Visit their website for more details.

This article was written by Duraflo’s marketing team. Roof Centre assumes no responsibility for any potential errors or opinions.

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