Calculating Ventilation Area of Attic

7 responses

  1. [email protected]
    July 17, 2012

    I have an attic, 50x40, with roof height 35ft. new roof calculated for 8 vents at the top, please help. philip

    • Tim Carter
      January 11, 2013

      Phillip, you need to schedule a 15-Minute call with me. There's simply too much to talk about and type.

  2. vinokaran
    December 12, 2012

    good work

  3. Deb
    June 20, 2015

    We have a sunroom with its own attic space. It's only 8×10. Do we need to ventilate such a tiny space? According to the math, it's .26 sq ft.

  4. Michael Glaser
    July 4, 2015

    How come you only calculated using the 1:300 rule? What about the 1:150 rule. There seems to be some situation when you use one or the other but you never discussed that. Could you discuss that?

  5. Kenny
    August 12, 2015

    Michael Glaser is correct. The 1:300 is used when calculating equivalent roof/soffit venting. In that case, the resulting area should be applied to BOTH. When calculating a 60/40 scenario, 1:150 is used and then a factor of 0.6 is used to calculate the soffit vent area and 0.4 to calculate the roof vent (or NFA) area.

  6. Thad Castillo
    December 1, 2016

    Does attic space include the soffit/overhang space? or just the attic floor (footprint of house)?

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