Q&A / 

Roof Turbine Vents

DEAR TIM: My home has two of the spinning turbine vents. I have been told by several people that it is a good idea to stuff insulation in these during the winter months so that warm air is not sucked out of my attic space. Is this good advice? Are these turbine vents really effective? I don't see many of them on my neighbors' roofs so I wonder if I should remove them. Kevin M., Canal Winchester, OH

DEAR KEVIN: Don't touch those vents! They are splendid ventilation devices. In fact, I installed these same vents over 25 years ago on the second home I owned. They were hardworking devices that Mother Nature paid to operate. In fact, the same vents are still in place on the home and each time the slightest breeze blows, they do a great job of pulling air from the attic space.

A turbine vent is a passive ventilation device. The popular ridge and soffit ventilation systems and the traditional metal pot vents are also passive ventilation systems. In contrast, an active ventilation device might be an electric powered whole house fan or a powered roof ventilator. Passive vents work for free and in almost all instances are silent.

The last thing you want to do is stuff insulation in the vents. Ventilating attic spaces in winter months is often more important than venting them in summer. Water vapor from the inside of a home can drift up and into an attic space. If this water vapor is not quickly exhausted to the exterior atmosphere, it can often condense upon the cold roof framing members and the underside of the roof sheathing. It can get so bad that water can drip from the underside of the roof and when the temperature gets low enough, frost can actually form up inside the attic. Moisture conditions such as this can lead to wood rot and mold growth.

Depending upon the diameter of the vents and the wind speed outdoors, the turbines can expel vast quantities of humid air before it becomes a problem. A small 12-inch diameter turbine vent with a constant wind speed of 5 miles per hour (mph) can remove 347 cubic feet of air per minute (cfm) from the attic space. A single 14 inch diameter turbine vent that is subjected to 15 mph winds can expel up to 1,342 cfm of air! If the winds are still, the vents still allow air to drift up and out of the attic space, although not nearly as much.

It is also a myth that turbine vents remove warm air from attic spaces in winter months. If the air temperature in your attic space is very warm while it is cold outdoors, I maintain that you might have inadequate insulation and/or you are up in your attic on a bright sunny day where the radiant energy of the sun is heating the attic space.

It is best to check attic temperatures at night after the sun has gone down.  If your attic is well insulated, the actual temperature of the air inside your attic should be very close to the actual outdoor temperature.

However, it is possible for turbine vents to pull conditioned air from the inside of your home. Modern building principals and most model building codes mandate that you have soffit ventilation vents that act as intake air locations. As air is pulled from the attic space by the turbine vent, ridge vent or even an electric powered fan, the same amount of air must be allowed to flow into the attic space where the roof passes over the exterior walls of the home. If there is not enough soffit air coming in, then the vents may create a partial vacuum in the attic space. To relieve this pressure, the vacuum may pull air from the inside of your home. This is not a good idea.

If you decide to add more turbine vents to your roof, be sure to buy ones that are aluminum. These will not rust. In addition, pay attention to the maximum roof pitch that will work with the turbines. The turbines are adjustable so that the spinning part is level even though the roof is slanted. Not all turbines will fit all roof pitches. The maximum roof pitch is almost always printed on the box label. Finally, be sure the ball bearings are permanently lubricated and sealed. Nothing is more bothersome in the middle of a windy night than a squeaky roof turbine!

Column 442


41 Responses to Roof Turbine Vents

  1. Are turbine vents water-tight or will external rainwater be able to enter the vent and possible get into the room interior??

  2. Isn't 'well insulated' when the outside and inside temperatures are slowed from balancing out right away? You make it sound like making something well insulated means having it open to external temperatures rather than locked off from them.

  3. I would like to put a 14" in the middle of my garage roof so it won't be so oppressive out there when the temp is over 90.
    Problem is we can get well over 2 feet of snow in the winter. How did you deal with that in Ohio?
    And, should I put some diverter rails above the turbine

  4. Me and my husband notice that we don't have
    The vents turbine vents on the roof. We didn't know if this was a bad thing and wanted to know
    Thank you .

  5. I have 4 roof turbines. One was sqeeking for a bit, then stopped spinning. I am worried that if it starts raining, will this cause water to drain into the attic if its not covered? I teally need an answer. And if the turbine needs to be replaced how much is the 14 inch black ?

  6. my roofer is telling me my turbans are to close to my roof vents and this can create a problem. He states the turban can pull rain water into the attic.

  7. My husband n I
    just bought a home. I noticed rope on vent to keep it from spinning should we take the rope off it is hotter in there than outside.

    • The turbine vents should be allowed to spin. Don't count on one or two turbine vents to lower attic temperatures significantly. You need TENS of THOUSANDS of cubic feet of air per minute passing through the attic to get the temperature to drop.

  8. I'm thinking about installing a wind turbine ventilator in my very hot garage. Should I be concerned about - or take any precautions to insure a necessary air supply for - the natural gas powered water heater in the garage?

  9. Do rotary turbines need to be installed where are above the ridge line to catch wind from all directions? I just had a new roof and whirlybirds installed and I can't see them from the front of my house while standing in the street. When I drive down the street, I can see my neighbors whirlybirds from the street. The roofers installed a whirlybird in the hole where an non working electric attic ventilator was located 40 inches from the ridge line . Then they lined up the other whirlybirds with it. For them to operate effectively, should they be visible above the ridge line, even if barely above the ridge line?

    • They don't have to be near the peak, but when placed there, they remove more of the hot air trapped under the peak.

      I prefer to locate them so they're NOT VISIBLE from the street. Believe me, they'll spin if not peeking above the peak!

  10. My home is a southern ranch that doesnt have an attic. I want to install some wind turbines to remove excess humidity and associated cold when the weather during the colder months and rainy season make my house uncomfortable to live in. The volume of my home is just under 12,000 square feet. What is a good APH (air changes per hour) to keep my house comfortable, and what size and how many wind turbine ventilators would you recommend me having installed? Many thanks for taking the time to answer!

    • It's not too bad. The trick is to make a horizontal slit in the metal roof that's the EXACT width of the base flashing for the turbine vent. The top 2/3s of the vent base flashing slides up UNDER the metal roof.

  11. Good day

    Do you have a specifications table or chart for such ventilator that have ventilator speed Vs wind speed, and dimensions… etc. I want more information for my company project.


  12. I HAD plans on trash bagging mine up for the winter I just installed but not now! Thx Tim! Besides they look cool huh? I'm digging the glossy black. Being a musician with jams indoors and out the black is so cool!

    Gonna pick up a couple more and have a turbine party soon!

    • If a storm creates a hole in your roof, water will get inside. Unless...... unless you know a group of wizards, I belong to such a group here in NH, that will cast a protective spell on your home and all it's underwater allies.

  13. Hi, the house that we bought had a turbine and i've seen it rotating but winter comes, i noticed it stop rotating for a couple of weeks now. Is there problem to that? Thanks!

  14. my whirleybird freezes in the winter since I upgraded the insulation in my attic. there are also eavestrough vents, but the whirleybird looks like a big snowball. we knock the snow off, but need to figure out what's going wrong. I live in Saskatchewan and so we are dealing with very cold winter temperatures. any suggestions?

    • You must have VAST amounts of water vapor in the home that's escaping into the attic as it should. This water vapor then FREEZES to the cold metal of the turbine vent. Explore what might be causing so much water vapor in your home. READ all my past columns about WATER VAPOR.

  15. I have eve vents and a turbine vent in the house i just bought. I want to finish the space how can i finish it? Do i need to install a new roof and ridge vent to finish the attic space bedroom. Thanks!

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