Turbine roof vents

(Paul Hinsperger, CMI) #1

In an effort to explain to a client why turbine roof vents are not a good thing I produced the attached graph.

It shows graphically that there is an inverse relationship between when the attic space needs the most venting and when the wind is blowing the most. So the turbine is;

  • working its hardest when its needed the least
  • working the least when its needed the most
    The second point then brings up the question - When its working the least is it still working enough? I would suppose that would vary greatly on individual instalations.

The velocity of a spinning turbine can be attributed mainly to the force of exterior wind. The spinning from the force of air rising from the attic through the turbine is minimal in comparison.

Certainly there are also other issue regarding turbines such as noise and depressurization which in themselves may be reason enough not to use turnbinbes but I mainly wanted to illustrate the basic venting effects.

The actual data used to plot the graph is from weather data from my local area but I suspect most northern non-coastal locations are similar.

(Joe Funderburk, CMI) #2

I'm not sure I concur that a couple of strategically placed turbines are less effective than, say, a ridge vent (provided that an air intake is available). I appreciate your efforts, but I don't understand the graph at all (the way you've scaled it, it appears to me that wind increases in correlation to a rise in temperature).

(Roy D. Cooke, Sr) #3

If for no other reason then that they always become noisy this is enough for me to not have one.
They in high wind pull air from the home ,not a good thing .
I have seen insulation missing from the attic and saw it on the ground , not a good thing.
I have seen snow in the attic under the turbine ,not a good thing .
I have not talked to an experienced home inspector in Canada who feels Turbines are any good .
Roy sr

(Joe Funderburk, CMI) #4

We don't get much snow down here. My mother's house has 2 turbines that have been working perfectly for about 15 years now. I don't know which is "best" but I know power vents have their problems too (including adding to the power bill).

(Russel Ray) #5

I'm a big fan of turbine vents.

What many seem to misunderstand is that they work with or without wind. They do not depend on wind alone in order to function.

Remember that hot air rises, so the placement of turbine vents can be critical. They should be up as high as possible, and they will work best if there are some soffit vents or static vents below them, as low as possible.

As the air in the attic heats up, the heat will rise, going through the turbine vents. The hotter the air, the faster it rises, and as it goes through the turbine vents, the turbines will spin. As they spin, they pull more air out. The hot air, the vents, and the resulting wind (or with external wind) work off of each other to create a very nice ventilation system.

If you have snow or rain in the attic, then the vent has not been installed properly.

If your turbine vents are noisy, they either have not been installed properly, you don't have enough insulation in the attic, and/or you need to upgrade from the 40-year-old turbine vent to a modern one.

My neighbor, at my recommendation, had two turbine vents installed when he re-roofed his house last summer. He reports that the attic is about 30° cooler post-turbine as opposed to pre-turbine. They are constantly in their attic since they store stuff up there. And in our daily sunshine here that lasts for about 11 months, his turbine vents are always spinning, with or without wind.

(Steve Boozer) #6

Ventilation is an issue you’ll get 100 different opinions on. I don’t like the turbines and they can make some bad squealing noises at times and are prone to damage from tree limbs. We usually put ridge vent everywhere we can where it is applicable except for the main attic. You get alot of square inches of opening. I guess at least 96 inches of opening for only a 4 foot section. I usually go with power roof vents in the main attic here in GA since the HVAC units are generally located there. I’m told the cooler the units stay, the better they work. PRVS can make some noise and do need replacing, but anything with a motor and a fan has to be the best at making air flow. Lomanco has a nice design. Metal screen, aluminum hood and base, rain shield and even a test button on the thermostat. I especially like the fact that they are the only one I’ve seen that does not have a seem only 1 inch up from the roofline.

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(Russel Ray) #7

Hmmmmmmmm. Me thinks that if the tree limbs are that close to your roof, you've got other issues to deal with as well. Those tree limbs should be trimmed away from the roof. There's such a thing as trees providing shade, but they should never be that close too your roof.

(Paul Hinsperger, CMI) #8

Hi Joe,

I don't know about the weather patterns or venting dynamics in South Carolina so maybe they work well in your area. I only know that in my climate they do not work as well as people think. More venting in the winter and less venting in the summer. :(

The aqua colored line is the wind speed. During the summer months when the temp and humidity are the highest there is less wind speed then during the winter months.

I think that people purchase them because they can see something spin - ergo it must something must be happening. Unfortunately something is happening, just not the way they think.:roll:

I also see that when a long attic space is vented with a turbine placed even in the middle of the run that there is more ice damming than usual near the ends of the roof. I have seen this on more that one occasion. The problem is that the turbine technically may have enough the exhaust output for the upper venting requirements but as it pulls the warm air from the living space near the ends of the attic, the heat from that air has been transfered to the snow on the roof before it can get all the way down the attic and exhausted through the turbine. More evenly spaced static vents or a full length ridge vent would work alot better.

Again let me say that I am talking about northern non-coastal climates here. In other climates they be fine.

(Raymond E. Wand) #9

The bearings sieze up on cheap models. They can allow rain and snow entry regardless how installed.

They can depressurize the attic, if there are not enough soffit vents. This depressurization can cause further problems particularly during winter months when moisture laiden air can enter the attic from attic penetrations. Particularly important consideration in winter months in cold climates, like Canada.

I would not install them, nor do I recommend them.

Thanks Paul.

(Dale Duffy) #10

Their a "Hot" item in Arizona. I generally see them still operating fine after 15 years plus. One can tell if they were installed on all the homes in a subdivision originally, they are located in the same portion of all the roofs.

Great source of ventilation in the desert.

(Charles R. N. Crooker, CMI) #11

Maximum for a better vent. Have a look at www.ventilation-maximum.com ,no moving parts and different sizes , to each his or her own!!:)

(Russel Ray) #12

T'was a little typo there.

Try this one:

www.ventilation-maximum.com

(Charles R. N. Crooker, CMI) #13

thanx RR T'is early, but still a good vent!;-)