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How many vents are needed on a roof?

 If you went to a new car dealership and you bought a car or truck with a gasoline engine, would you then go down the street and put diesel fuel into the tank? No, that would void the warranty and then it wouldn’t work as intended!

Yet that’s what thousands of home owners do every year by not having proper ventilation on their roof. But how do you determine how many roof vents you need?

Looking at square footage

Oklahoma has adopted the 2015 International Residential Code, IRC. That means that by code, you’re supposed to have two things:

  1. Equal intake and exhaust
  2. One square foot of exhaust ventilation for every 150 square feet of attic space

Unfortunately, Oklahoma is notorious for having very bad ventilation on houses. We have to increase the amount of exhaust ventilation on nearly every house where we replace a roof.

Square footage of your attic is different than square footage of your home

A lot of people assume that the square footage of their attic is the same as the square footage of their house. That is not the case.

Several factors can cause your attic square footage to be much higher than your home’s square footage:

  • An attached garage with attic space above it
  • A covered patio in the back yard with attic space above it
  • A covered front porch with attic space above it
  • The roof itself and its attic space extending beyond your home’s foundation by one or two feet

All of those things will factor into determining the true square footage of the attic. So, what we do—and anyone else in Oklahoma County or Cleveland County can do this—is go to the county assessor’s website, look up your property to get the county assessors footprint sketch, then we physically measure the additional square footage to come up with the actual square footage of the attic.

Then we install the appropriate amount of exhaust vents based on that square footage.

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