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Community and Q&A

Soffit Vents + DCI Smartvent: good idea or bad?

heartnhome | Posted in Energy Efficiency and Durability on

When I bought my house, we had to have the roof replaced (standard vented roof assembly) – the roofer said the soffits were sealed, and installed DCI Smartvent mid-roof for air intake.  It’s now come to light that the soffits are not sealed at all – wide open!

Do the open soffits and the Smartvent mid-roof work together or cancel each other out?  Is it wise to seal the soffits and leave the Smartvents open?

If sealing the soffits we’ll probably go from the outside.  We have some leftover polyiso – was thinking about putting in new blocking, sealing soffits with pieces of polyiso, and then attaching a decorative soffit on top of the foam – probably back vented for drying – see attached back of envelope sketch.

Thanks for your feedback in advance!

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  1. Expert Member


    Roof ventilation moves air primarily by two mechanisms: the stack effect and wind. To effectively remove moisture you also want the air to move over the entire area of the underside of the roof. So for effective ventilation you want the intakes at the bottom and the outlets at the top of a well sloped roof.

    It's hard to know what effect the mid-roof vents have. They may increase the volume of air the soffit vents bring in, they may decrease it. They almost certainly increase the amount of ventilation at the peak where it is most valuable. If you were going to block any vents it would be them, although I'd be inclined to leave things alone.

    1. heartnhome | | #2

      That all makes sense - thanks for the advice!

  2. Jon_R | | #3

    I'm curious - if the purpose of the Smartvents was to replace soffit vents, why were they installed mid-roof (vs eaves)?

    1. heartnhome | | #5

      Great question - don't know. When the roof was being redone I hadn't learned about or even known of the idea of building science. Otherwise, I would have the roof done completely differently.

  3. GBA Editor
    Brian Pontolilo | | #4

    Hi HeartnHome.

    I don't think you have a problem. Most of the experts I have talked to about attic venting agree with this Q&A with Bruce Harley (Should I Close My Attic Gable Vents?), don't overthink it. There is one caveat, though: it is important that your ceiling is well air sealed so that the primary mechanism mentioned by Malcolm above, the stack effect, isn't pulling conditioned air out of your home.

    1. heartnhome | | #6

      Thanks for the input - working on the air sealing piece as we speak.

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