# Attic solar fan



## Oso954 (Jun 23, 2012)

I would suggest that you get a pro to review your attic venting. 

Often multiple vents on the roof are a sign of people adding vents hoping to improve the situation. So they can be a sign of other problems such as not enough (or large enough) soffit vents for air entry.

A common problem with power vents (solar or not) is locating them too close to another roof vent. You can end up pulling fresh air in the exhaust vent and have it exit the power vent, while leaving most of the overheated attic air undisturbed.


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## jesusq (Jul 7, 2014)

If that's the case, a fan would be a waist. I have 8 easil on the lower attic and about three vents on the top of the attic. If that's the case, I can convert one of the vents to a fan. But would there be any significance to adding a fan?


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## LeakyHawaiiRoof (Oct 21, 2014)

My parents have an attic fan, but they don't have air conditioning. From what I can tell, their attic fan works generally well. Their attic gets crazy hot and sucking out the hot air helps to keep the house cool.

I think the major factor for getting an attic fan is that the air outside the house must be cooler than the air inside the house. Basically, hot attic air gets pushed out through the attic fan and that sucks air from the house into the attic. This sucks the cooler outside air into the house the house through the windows. And the house feels cooler

If the air outside the house is just as hot inside the house, then it doesn’t make much difference. 

One additional thing is that my parents' attic fan is solar powered and it need direct sun to work. So when the sun goes behind a cloud or moves to the other side of the house, the fan stops spinning and that's not ideal. 

From what I've read if you have air conditioning, an attic fan may not reduce your cooling costs.


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## jesusq (Jul 7, 2014)

My though is that if I insulate the attic and remove the hot air by placing a fan, my thought would be that the air condition won't have to work as hard to keep the house cooled.

Now my questions is how much easle and vent is too much or too little for an attic fan to be effective or a waste of money and time?

What do you go by to decided if an attic fan would be effective?


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## Gary in WA (Mar 11, 2009)

http://www.greenbuildingadvisor.com...nce/are-solar-powered-attic-ventilators-green

http://www.ronhungarter.com/black_mold.html

http://www.fsec.ucf.edu/en/publications/html/FSEC-GP-171-00/

Gary


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## jayp526 (Jul 15, 2015)

I had an existing gable vent and I retrofitted a 20 watt solar fan and thermostat. It made a substantial difference in the amount of heat in the attic. I took it a step further by putting in an insulated radiant attic barrier and I no longer have issues with cooling my house. I've been kicking myself that I didn't do it sooner and have been needlessly sitting in a house that the temperature ran 8 degrees above the set temp in the summer. It turned out well, and I'm glad I did made the upgrade. Hope this helps!


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## Ron6519 (Mar 28, 2007)

LeakyHawaiiRoof said:


> My parents have an attic fan, but they don't have air conditioning. From what I can tell, their attic fan works generally well. Their attic gets crazy hot and sucking out the hot air helps to keep the house cool."
> 
> What you're describing is a whole house fan. It may be in the attic but it's not what the OP is talking about.
> He's talking about an attic exhaust fan that expels super heated air out of the attic while pulling in outside air to replace it.
> It's restricted to the attic space for the most part due to leakage in construction.


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## craig11152 (Jun 20, 2015)

There is a general rule of thumb in the industry that one should not mix and match various types of exhaust vents on a roof. This is particularly important if there are functional soffit vents. The idea is that air will follow the path of least resistance and some exhaust vent will become an intake for another exhaust vent and they aren't designed for intake. If one subscribes to that theory then a solar fan doesn't really fit in well to "balanced" venting.


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