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Attic fans

Discussion in 'Home Power and Microgeneration' started by John Dunkley, Sep 12, 2006.

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  1. John Dunkley

    John Dunkley Guest

    I am wondering if anyone has personal experience with attic fans?

    i.e. pumping hot air out of the roof space/attic during summer?

    Would be interested to know if it is worthwhile.

  2. Guest

    How do you figure 'theoretically most effcient'? I'd say more is cooler.

  3. Jim Baber

    Jim Baber Guest

    Jim Baber wrote:

    John, there are also "wholehouse fans" for you to consider as well.
    If you are not familiar with them, they are installed in the ceiling
    below the attic near the center of the house, and pull warm air from the
    living areas and push it into the hot attic thereby forcing that hotter
    attic air out of the attic.

    These fans are very effective if the inside air is warmer than the
    outside air, but they do require that you open windows or provide
    another source of outside air in the living areas.

    My wholehouse fan reduces the need for air conditioning by about 6 hours
    a day in 100+ heat and 10 hours in 90 - 99 heat, and eliminates A/C
    below 90 when I am trying to maintain a 79 degree temp. in the summer in
    Fresno CA. It works this well, because of our usually low humidity.
    The nights usually are below 80 after 9:30 - 10:30 even on most 100+ days.
    It requires that you also have very good attic venting, I have 3
    turbines and several regular regular vents. I have found that
    occasionally on very hot days if I run the wholehouse fan for a short
    time occasionally, it helps by forcing the super hot air from the attic,
    but that means I am pulling hot outside air in from the window (I just
    open one window near the fan), and that does not upset the general
    inside temperatures, but does cool the attic just like an attic fan would.
    Without a doubt. I am very sensitive to the temperature, and my health
    is such that I require A/C in the summers here. (this year beginning
    Jun 15 for the 90 days ending yesterday we averaged 99.5 degrees F. at
    5:00 PM) I was reasonably comfortable keeping the temperature in my
    house below 80, and yet I kept my actual a/c usage to a minimum.
    One thing I might mention, I cool the house as much as I can in the
    mornings before it gets hot outside using the wholehouse fan and even
    the a/c, BUT, then after noon or if the temperature outside goes above
    79, I close all windows and shut everything off until after 6 PM.

    I am on what PG&E calls Time Of Use metering, for the power I use. That
    means for the summer weekdays between noon and 6 PM, I have to pay 3
    times much for "Peak" power than what I pay for all the other "Off Peak"
    power we use. PG&E's obscene rates are why I have invested in solar PV
    to the extent that I have.
  4. John Dunkley

    John Dunkley Guest

    Can you give me a pointer to the type you are using please?

  5. Sorobon

    Sorobon Guest

    I installed an attic fan in my house in Spokane, WA it dropped the attic
    temp. from 120 to 100. That had to have an effect on AC costs. In 2 houses
    in the Southwest I installed vents that allowed the air from the roof swamp
    cooler to be vented through the attic rather than out the windows.
  6. John Dunkley

    John Dunkley Guest

    Now that is very clever!


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