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Solar powered attic fans? (Northern VA)

Funny this is a repair/replacement I need to do this spring. The top of my power vent blew off last fall and everything go fried so I need to replace it all. I didn't want to re-wire everything so I was thinking about one of these solar units too...
 
Not sure if pricing has changed much. I remember doing research a couple years ago and the consensus was that a solar attic fan would take something like 20 years to pay for itself.
 
yeah, I heard that they do very little to make any noticeable difference. I you have radiant barrier and 6" of foam, that good enough.
 
cbrsurfr said:
Not sure if pricing has changed much. I remember doing research a couple years ago and the consensus was that a solar attic fan would take something like 20 years to pay for itself.
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I think most of the appeal is not needing to run wiring for it.
 
None of them, solar or "electric" seem to last very long...Solar has the advantage of not using electricity from the grid...but they also don't work after the sun goes down...but your attic is still hot from the day's heat.
We considered a solar gable fan for our house in CA. Decided it wasn't worth the cost. Left the turbines on the roof...and moved out of CA. 😛
 
I had a powered fan...3 of em. All they did was make noise. 100+F here in the summer.

Zero...0...difference in attics temps without them vs with them.

A well ventilated roof doesn't need them.
 
Tsavo said:
I had a powered fan...3 of em. All they did was make noise. 100+F here in the summer.

Zero...0...difference in attics temps without them vs with them.

A well ventilated roof doesn't need them.
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interesting.

my powered attic fan lowered the temps in my 2nd floor bedroom by 3 degrees.
my bedroom was at 79 degrees. it's now 76F at the same central a/c settings.

and my roof has a roof cap/ soffits.
 
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Yeah, I'm not sure where they pulled that 1200 sq. ft. number from, but you're not going to be moving much air with 10 watts. I have had computer case fans that used more power than that.
 
I have an electric one rated for 1200sq feet. It pushes 1650 cfm. I think they are rating it a bit high. It's 9 years old and still going strong. Running wires is simple.
 
natto fire said:
Yeah, I'm not sure where they pulled that 1200 sq. ft. number from, but you're not going to be moving much air with 10 watts. I have had computer case fans that used more power than that.
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Agreed, also a cubic feet would have made better sense, sqft does not mean much when attic height varies a lot, the roof angle changes from place to place, from builder to builder. The rating is Ox excreta.
 
Here I see mostly non powered/mechanical vents now days. Still see lot of whirlybirds too but most people end up replacing them with non mechanical vents.

These are quite popular:

http://www.homedepot.ca/product/sloped-roof-ventilator-model-301-black/981033

They let lot of air out and are decently high that they don't get covered in snow. The peak of the roof where these are typically installed tend to not get as much snow, probably because of wind currents. Through convection air gets out and then sucks new air through sofit venting. There's always going to be a bit of heat loss through the insulation.

So you can probably get away with something like that, really. The powered fans will move more air though, so you can probably get away with less top venting by adding a single powered one instead of a row of passive ones.
 
Red Squirrel said:
Here I see mostly non powered/mechanical vents now days. Still see lot of whirlybirds too but most people end up replacing them with non mechanical vents.
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Whirlybirds suck (or rather stop sucking) if you live in the frozen tundra. :biggrin:

OP does not have to worry about snow, being in VA.
 
Drako said:
Whirlybirds suck (or rather stop sucking) if you live in the frozen tundra. :biggrin:

OP does not have to worry about snow, being in VA.
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Not really the snow, as if they're on top of the roof and tall enough they're usually ok, the problem is the bearings start to go after a while and it keeps the whole neighbourhood awake. 😀 One time one of my neighbour's was going crazy during a storm in middle of the night, then it finally stopped. The next day I noticed someone through a rope on it to force it to stop. I thought that was hilarious. Not sure if it's the owner himself or someone else that did it. lol
 
Attic fans are awesome only whenever outdoor air is cooler and drier than indoor air. Obviously any air pushed out of the house must be drawn back into the house through holes or leaks.

An even better idea might be to keep heat out of the attic (and from other parts of the house) with a properly installed radiant barrier. It also has the benefit of keeping heat from escaping during the winter.

https://www.youtube.com/user/AtticFoil
 
bradley said:
Attic fans are awesome only whenever outdoor air is cooler and drier than indoor air. Obviously any air pushed out of the house must be drawn back into the house through holes or leaks.

An even better idea might be to keep heat out of the attic (and from other parts of the house) with a properly installed radiant barrier. It also has the benefit of keeping heat from escaping during the winter.

https://www.youtube.com/user/AtticFoil
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I don't know about other parts of the country, specially snowy regions, but here in TX, there is a good amount of gap between the wall and the roof, this is for the attic to breathe. Its designed in such a way so that it keeps bugs, scorpions and squirrels out but allows ample air flow. When I get into the attic I can see significant amount of light coming through the area where the roof and the wall meets.
 
deadlyapp said:
had something similar to this in my last house: http://www.globalindustrial.com/p/h...mpaignId=T9F&gclid=CIu8jby77MQCFQwDaQodjTIADw

No idea if it was directly vented to outside or just was used to pull air into the attic. It seemed to work very well if we opened a few windows on the downstairs floor and upper bedrooms and kept all the doors open. We could drop 5-10 degrees after the sun went down in a half hour or so.
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My coworker installed something similar and he said it's great for cooling the inside of his house. His house gets fairly warm inside even though he lives near the coast.
 
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