Attic Ventillation. Roof vents vs Whirly birds.

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topper
topper Solar Expert Posts: 113 ✭✭
in Energy Use & Conservation #1
Just finished shingling.. Installed 2 14" whirlybird roof vents approx 6" from the ridge.
House is 960 sq ft with a 4/12 pitch.
Soffit venting = 7 1/2 sq ft.
Any thoughts on which is better. Standard roof vents or whirlybirds?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #2
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    Re: Attic Ventillation. Roof vents vs Whirly birds.

    I think the whirlybird (turbine) vents don't actually improve air flow--They help to prevent back drafts (wind blowing back down the vent). For a fireplace, back drafts are smoky affairs. For an attic vent, I am not sure a back draft would hurt anything.

    The websites claim they do move more air with wind flow--but so would most other vents too. And you probably want to look for good quality turbine vents with sealed bearings. Open bearings/bushings are going to be squeaky and required constant maintenance.

    It sounds like you have plenty of low vents (Soffit) but not nearly enough up high.

    In the end, you need lots of sq.in. of openings (both high and low) and I am not sure that enough turbines on the home without it looking like factory.

    You can review current code and other suggested vent to attic ratios (seems there is lots of disagreement on the details).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
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    Re: Attic Ventillation. Roof vents vs Whirly birds.

    Full-length ridge vent, in combination with soffit vents, is best.

    The "whirly bird" or "turbine" vents are worse than useless. It is a con to make people think the spinning action is like running a fan and mechanically drawing hot air out. It doesn't. They make noise too.

    Worst of the worst is having different kinds of high vents on the same roof; you can draw air in one and out the other and never draft up from the eaves.
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  • topper
    topper Solar Expert Posts: 113 ✭✭
    #4
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    Re: Attic Ventillation. Roof vents vs Whirly birds.

    Locals have informed me that the full length ridge vents work well up here in the summer but seem to redirect blowing snow into the attic.
    Fact or fiction????
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  • jcgee88
    jcgee88 Solar Expert Posts: 154 ✭✭
    #5
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    Re: Attic Ventillation. Roof vents vs Whirly birds.
    Cariboocoot wrote: »
    Full-length ridge vent, in combination with soffit vents, is best.

    I agree with this assessment. I once had turbine vents installed,
    and when I last got my roof replaced (due to hail damage), the roofer
    recommended low profile vents. He told me that the turbine
    vents were useless. While I did put in the low profile vents, if
    I had the choice to do again, I would get the full-length ridge
    vent, as my attic still gets toasty in the summer.

    Also, if I still had turbine vents, they would cause shading on
    my solar array!

    John
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  • dagr51
    dagr51 Solar Expert Posts: 72 ✭✭✭✭
    #6
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    Re: Attic Ventillation. Roof vents vs Whirly birds.

    I've installed many full length ridge vents in snow country without a problem of any kind. It's what I put on my own stuff, FWIW.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: Attic Ventillation. Roof vents vs Whirly birds.
    topper wrote: »
    Locals have informed me that the full length ridge vents work well up here in the summer but seem to redirect blowing snow into the attic.
    Fact or fiction????

    Since it's an outlet for escaping air, it can't redirect air (and any snow it might be carrying) back in to the attic.

    There are sometimes problems in high snow areas with ridge vents being blocked by accumulation, and such could find its way inside - through any type of vent (there are special high vents for just such an occurrence, if needed). If your ridge vent gets block by snow build-up, it means someone didn't slope the roof properly for your area; snow should not be allowed to get that deep on a roof. This happens more often than it should, sorry to say; people just build any old style anywhere with no regard to local environment. :grr
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  • topper
    topper Solar Expert Posts: 113 ✭✭
    #8
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    Re: Attic Ventillation. Roof vents vs Whirly birds.

    OK Thank-you all for the input.
    I very seldom have issues with excessive snow buildup. Once every 5-6 years with sticky snow and the right wind. That is what a roof rake is for.
    I'll patch the 2 holes and install a full length ridge vent. With new shingles < week old it should be a breeze.
    Hind site is always 20/20.. Should have inquired prior to roofing.

    Ken
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #9
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    Re: Attic Ventillation. Roof vents vs Whirly birds.

    I had a turbine vent, and it's lifetime bearings lasted about 3 years. Then it squeeked till I re-roofed and replaced it with a dormer vent.
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  • peakbagger
    peakbagger Solar Expert Posts: 341 ✭✭✭
    #10
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    Re: Attic Ventillation. Roof vents vs Whirly birds.

    Snow on my ridgevent happens every year with no evidence of snow coming in. I also have gable end vents on either side of the house and have gotten snow in even though they have slats and screens. I made a plastic lined tray that sits inside the vent to capture any snow if it happens.

    I am an advocate of gable end vents in addition to ridge vents as I have seen houses with ice damming issues when the roof vents are covered with snow. Once the snow is cleared the gable stop iceing up but after a heavy storm it can make a mess.
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  • YehoshuaAgapao
    YehoshuaAgapao Solar Expert Posts: 280 ✭✭
    #11
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    Re: Attic Ventillation. Roof vents vs Whirly birds.

    I've read that large dormer vents work very well, but they are often very ugly with retrofits (I saw a neighbor who reroofed and had 4 of them, and they were ripped out and replaced with whirly birds within a few days)
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  • Chris
    Chris Solar Expert Posts: 135 ✭✭
    #12
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    Re: Attic Ventillation. Roof vents vs Whirly birds.

    As a Journeyman, (Red Seal) roofer I've installed thousands of roof vents......by far the best ones money can buy are either ridge vents/low profile (Lameko) as long as you have enough of them....... or if you can get your hands on some, "Phenix" vents. The wost thing you can do is install more then one whirley bird on a roof as they will cause cross venting.
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  • Ken Marsh
    Ken Marsh Solar Expert Posts: 114 ✭✭✭✭
    #13
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    Re: Attic Ventillation. Roof vents vs Whirly birds.

    Agree, soffit vents with ridge vent is the way to go.
    But I once did have a bad house fire with this.
    The house had some 12 inch of blown cellulose in the attic.
    The vents allowed enough wind to get in to the attic to blow the insulation around.
    It piled up around a stove vent, totally enclosing it which eventually started a fire.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #14
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    Re: Attic Ventillation. Roof vents vs Whirly birds.
    Ken Marsh wrote: »
    Agree, soffit vents with ridge vent is the way to go.
    But I once did have a bad house fire with this.
    The house had some 12 inch of blown cellulose in the attic.
    The vents allowed enough wind to get in to the attic to blow the insulation around.
    It piled up around a stove vent, totally enclosing it which eventually started a fire.

    I had a similar experience with wind moving blown-in insulation around to the point where some areas had none and others it was twice as thick as needed! :p
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  • Ken Marsh
    Ken Marsh Solar Expert Posts: 114 ✭✭✭✭
    #15
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    Re: Attic Ventillation. Roof vents vs Whirly birds.

    So Coot, did you do anything to stop or slow down the migration?
    We repaired the house and put the same insulation back in.
    So I suppose it could and probably will happen again.
    But I did move the wood stove to another place that has bat insulation.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #16
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    Re: Attic Ventillation. Roof vents vs Whirly birds.
    Ken Marsh wrote: »
    So Coot, did you do anything to stop or slow down the migration?
    We repaired the house and put the same insulation back in.
    So I suppose it could and probably will happen again.
    But I did move the wood stove to another place that has bat insulation.

    Yep. Spent days putting it back to right levels (Tudor style house; crawling in the space between roof and ceiling), sealed it over to prevent air and insulation movement. Did the same to the exposed fibreglass in the wall structure of the area (air moving over that will pull heat out too). Also had to seal the ends of the floor/ceiling joists as the gaps between were open from one eave to the other. Made a HUGE difference in heating costs and home comfort.
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  • Chris
    Chris Solar Expert Posts: 135 ✭✭
    #17
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    Re: Attic Ventillation. Roof vents vs Whirly birds.
    Cariboocoot wrote: »
    I had a similar experience with wind moving blown-in insulation around to the point where some areas had none and others it was twice as thick as needed! :p

    Where bouts in BC are you that you got hurricane force wind? LOL
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #18
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    Re: Attic Ventillation. Roof vents vs Whirly birds.
    Chris wrote: »
    Where bouts in BC are you that you got hurricane force wind? LOL

    It takes surprisingly little wind speed to blow through eaves and lift loose fibreglass fill.
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