Whole house fan

Discussion in 'HVAC' started by maxdad118, Jul 25, 2018.

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  1. Jul 25, 2018 #1

    maxdad118

    maxdad118

    maxdad118

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    I’m considering installing a whole house fan due to the simple fact I’ve seen great results from them. I have an old gable vent fan new in the box, I was wondering how that would work as opposed to spending $800-$1000 on one of the prefab kit’s? I’ve watched a few YouTube videos as well and seen simple box fans used!?my house is a little over 1500 sq ft. Any insight on what to do or tips?
     
  2. Jul 26, 2018 #2

    joecaption

    joecaption

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    #1, What's your location!
    Whole house fans work great but trying to use a gable fan to do the job is not a great idea.
    Still going to have to buy the louvers that go in the ceiling, make a frame to mount it to.
    As well as gable vent fans are meant to be mounted vertical and you need a horizontal mount.
    Not sure how the bearings used in that fan are going to like that.
    Tell us about what type roof you have and how it's vented.
    Does no good to blow the air into the attic and have no place for the hot air to go.
    You can find almost any goofy thing on Youtube, OK so you cut a hole in the ceiling and set a box fan over the hole, yup air blows into the attic.
    OK now what happens when you shut it off and and want to use the A/C, now you have an ugly open hole in the ceiling leaking air if there's no louvers to shut off the air flow.
    What I have seen done once was someone already had a gable vent fan so they redid the wiring so there was a switch in the hallway added the louvers in the ceiling and built a duct out of 1/2" plywood and 2 X 4's .
    Worked perfect and made far less noise when running.
     
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  3. Jul 26, 2018 #3

    maxdad118

    maxdad118

    maxdad118

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    Yeah, I won’t use the gable vent fan, makes sense. I’m in Northern California. A few sofet vents and lo profile vents. No ridge vent but 1 gable vent and fan. I’m not willing to spend $2200 like a neighbor was quoted, im willing to buy the right product and install myself. I hear I need about 1 cu ft of attic vent space per 750 cfm? Does this sound right? So my current situation doesn’t allow a whole lot of options. May need to cut out more sofet vents? I’m no roofer but I’d imagine a ridge vent would be ideal?
     
  4. Jul 26, 2018 #4

    Snoonyb

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    The Ideal condition for a whole house fan system is to draw cooled air from a shaded and/or grassy area, preferably east facing, and push the heated air into the attic, which is then vented, essentially cooling the house.

    The gable end vent will be to small to be efficient so you could add some fixed low profile roof vents or some whirlybirds.

    Soffit/eve vents are, by there placement, meant to facilitate air flow and venting for the attic through the gable end vent, and the flow is low to high, because heat rises.

    Because of the color of your roof and the stucco you'll have heat gain into the evening, so a timed switch may be in the offing.

    The difficult part of the "kit" installation is the electrical, the rest is pretty straight forward.
     
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  5. Jul 26, 2018 #5

    slownsteady

    slownsteady

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    I have had a gable fan in this house since I moved in. It is mounted vertically at (of all places!) the gable. Before I added ridge vents, the fan worked great, pulling air up through the house and evacuating the hot air from the attic along with it. The ridge vents definitely reduced that pull, and made it less efficient, but it still works. Over time we discovered that it works best in the early morning and overnight, as it is pulling cooler evening air into the house. We often turn it off during midday. Our house is pretty well insulated and somewhat shaded so it doesn't get too hot during those hours. I'm not a big fan of A/C, and being in the hills of north NJ allows us to live without it (although my neighbors think I'm nuts for not having central air).
    It doesn't matter which point of the compass the fan is located, because it is an exhaust fan. But it helps to open windows on the shady side of the house. And yes, we do have a louver in our upstairs hallway ceiling and a wall switch in the hall. You can get a programmable switch with auto settings at the bigbox.
     
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  6. Jul 26, 2018 #6

    Steve123

    Steve123

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    If the fan has ball bearings, it likely will be fine with shaft vertical. If it has sleeve bearings, its not as certain.

    But what I would be more concerned with is getting the quietest possible fan. Night-time would be a great time to run the fan (cool outside), but if it disturbs your sleep, its useless. Not sure how cold it gets in the winter over there, but the other thing to consider is being able to seal up the big hole in the vapor barrier. Warm moist household air, going through the opening and hitting a cold roof can result in condensation.
     
  7. Jul 26, 2018 #7

    mabloodhound

    mabloodhound

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    Soffit vents are not meant for "exhaust" but for intake of cooler air to keep the roof and shingles cooler. The gable or ridge vent is for the exhaust of hotter air. More soffit vents will NOT help you for the whole house fan. You need adequate gable or ridge venting for it to work.
     
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  8. Jul 27, 2018 #8

    Gary

    Gary

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    We have a whole house fan in my office above the soffit that runs around the perimeter of the room, so it's concealed a little. Attic has natural flow vents and several power vents that kick in when it really gets hot. We turn the whole house fan on in the evening with a couple windows open, then turn it off & close the house up in the morning once the house is cooled down. As long as we get cool nights it stays pretty cool during all but the hotest days.
     

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