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  1. #1

    Will it do anything to install fans in "gravity vents"?

    My girlfriend recently purchased a small condo unit on the 3rd floor of a 7-story building. Other than a single window, the only ventilation to the condo unit is from what the other building residents call "gravity vents". In the ceiling of the kitchen and bathroom are two roughly 8-inch square vents leading to ducts which presumably lead to the roof. I think the theory is that a breeze blowing across the roof will create a vacuum that will suck air from the condo units through these vents.

    (1) Given that there is no "inlet" for air into the condo unit (at least when the window is closed), do these "gravity vents" actually do anything at all? I am under the impression that these vents operate about as effectively as trying to suck the air out of a rigid straw with the other end covered up.
    (2) Would installation of fans at the vents in the ceiling improve the effectiveness of these things at all? I am under the impression that it would be futile to try to move a 4-story column of air with a dinky little ceiling ventilation fan.

    The housing association rules do not permit the door of the unit to be propped open so I am concerned that there will be no way to get fresh air in. Any suggestions?

  2. #2
    Correction, it's actually an 8-story building, so the fans would presumably be trying to move a 5-story column of air...

  3. #3
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    1,809
    Gravity is not the force which moves air. It is pressure differential, usually accomplished by a blower designed for the application. An 8" duct booster will not generate enough pressure to move enough air to make a difference. Also, there must be an inlet and outlet to achieve air flow.

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