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Question DetailsAsked on 4/11/2012

For attic ventilation can you use both whirly birds and ridge vents on your roof or do they compete with each other? If so, which is best?

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2 Answers

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4
Votes

Attic ventilation is a science that is unique to the architecture of each building. There are no one size fits all solutions. There is no "better" as a blanket statement without knowing more about the structure.


Ridge vent works well, with proper initake. All ventilations work more effeciently with intake, but some like ridge vent won't work at all without equal or greater intake when measured in Net Free Area (NFA).

Commonly if you have a hip roof, you may not have adequate ridge length for a ridge vent. This is a a VERY common mistake I see from unskilled roofers. For example a house with a 1,000 sq ft attic space would need not less than 27 linear foot of a good quality ridge vent like Air Vent II. That is to say if your house is 1,000 sq ft at the foot print, and you don't have at least 27' of ridge, a ridge vent is not Better, but is Worse.

Typically my rule of thumb is to stay away from ridge vent on hip roofs. So what then? Well I will then normally install what are sometimes called canned/mushroom.turtle breather vents. The same 1,000 sq ft home would need only 3 vent, assuming they have 144 NFA each. Without an intake you would need to double this number to make 6 roof vents.


I am not really a fan of turbines, aka whirrly birds. They do work, but they have been known to break down and are reliant on the wind. Without the wind they are nothing more than big ol' breather vents on the roof. If you chose to have turbines installed the "book" would say that you need 3 if they are 14" vents. However since they are not always whirling around, I'd say add another for safety sake. For this reason, as well as cosmetics, I would encourage you to consider the 144 NFA mushroom/turtle vents instead.



One thing most people agree upon is that you do NOT mix exhaust ventilations. Don't put turbines with ridge vent. Don't put mushrooms with ridge vents. Don't put mushrooms with fans near by. THis creates a short circuit meaning the two fight each other. Think if your turbine is spinning. It is pulling air. It is supposed to pull air from the soffit/intake vents. However it will choose the path of least resistance and pull air from the closest opening, ie: the ridge vent. This is why they call it a short circuit, it will interupt the path of air flow from the soffit and thus most of your attic will not be properly ventilated.


Source: http://reliableamerican.us/articles/a...

Answered 7 years ago by ReliableAmericanRoof

0
Votes

No, The shingle manufactures will tell you not to do this either one or the other.They would recommend closing in the turbine vents and installing the ridge-vent. See when you have to different types of exhaust vents such as these or even a power vent and ridge vent or gable vents and ridge vent,what happens is they will work against each other and the path of least resistance will make one a intake vent and one an exhaust vent.So the majority of the roof is not getting attic ventilation and therefore not venting properly..Go with a good ridge vent externally baffled..make sure you have attic soffit vents as well..

Answered 7 years ago by Ronnie1970

2
Votes

For future readers, AirVent is a great source of visuals and information.


Reliable is great on the roofing information and you do not want to mix ventilation types.


Best and ideal venting is passive and balanced.

Answered 5 years ago by WoWHomeSolutions




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