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Community and Q&A

Does attic rafter vent size matter?

bkeesaman | Posted in Green Building Techniques on

We are in NW Missouri between 5A and 5B. This is part of an addition with 24″ centers. The insulation company installed some rafter vents but not all. What they did install is smaller than the rafter span. I am putting rafter vents in the rafters that do not have any and air sealing the recommended areas. Should I replace the smaller rafter vents with bigger ones, too, or will it make a big difference? Thank you for the input. Pictures attached.

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  1. Expert Member
    Dana Dorsett | | #1

    There should be NO contact between the roof deck and fiber insulation AT ALL! Code demands 1" clearance.

    Whether there is sufficient total free air cross section to meet code needs to be measured and calculated:

  2. GBA Editor
    Martin Holladay | | #2

    Here are links to two articles that will guide you:

    Site-Built Ventilation Baffles for Roofs

    All About Attic Venting

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