Installing fans on gable vents?

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Hey all,
I'm thinking of installing a couple electric duct booster fans onto my gable vents to help remove the heat thats building up in the attic. One on each end, one pulling air from the outside on one side of the house and exhausting on the other side. Is there any drawbacks to doing this? Anything I should be concerned with?
Thanks all, Brian
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Powered attic fans have been shown not to be cost effective in homes with air conditioning. Ask you electric utility.
Ed

gable
Anything
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30 years ago I added 2 attic fans, one for each attic. I cut my AC running time on a 90+ degree day from 8 hours continuous to 3 hours continuous, plus the temperature didn't creap up during the mid day as it did w/o fans. I now have continuous ridge venting, so the fans are gone. If I were the power company, I would tell people not to use them either!
jagerEd wrote:

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Art, the problem is the things take power to run, and they run a lot.
The studies I referred to were done at what whas then the National Bureau of Standards (now NIST). They found that the power used by the fans exceeded that saved at the AC compressor on an annual basis. One problem is they are usually controlled by a thermostat in the attic, so they run any time the attic gets hot, even while you are on vacation. My neighbor has one so I have first hand experience with that issue. And it makes more noise than her AC!
I'm glad you got rid of them!
Ed
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I believe studies have shown whole house fans, drawing air from the house and out through the attic, to be cost effective, unlike powered attic fans which draw air from the outside, which are not. I'm not sure about running it all night though. Unless you have a lot of mass, e.g., uncarpeted concrete floor, tile roof, etc., it seems that thisngs are going to be about as cool as they are going to get after a few hours. PErhaps a timer could be used to turn it on only when outside air is coldest... midnignt to 6 AM.
Ed
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On Mon, 14 Jul 2003 15:18:36 GMT, "jagerEd"

We use it instead of air-conditioning. It gets hot and humid where we are quite often. On those nights, you want the breeze from the fan in the evening hours and into the night. Depending on the temperature fall and on whether I feel like getting out of bed at 2 or 3AM, it sometimes gets shut off then. Other nights it runs until I rise a 6AM or so.
By 7AM during the summer it is already starting to heat up so it needs to be shut off and the windows closed up to preserve the cool air. In a well insulated house, this keeps it comfortable most of the time aside from a few hours in the late afternoon on the really hot days. Those days you just open it up and turn on the fan to enjoy a little moving air.
As a side benefit, a whole house fan makes one heck of an exhaust fan when you burn something on the stove :-)
Bob
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In alt.home.repair on Wed, 16 Jul 2003 23:56:36 GMT 'nuther Bob

If I were to do that in the late afternoon, most of the hot days it is still hotter outside than my house is inside.
If I didn't have the roof fan, it might be hotter inside, but it would be no less hot outside. So running the whole house fan would give me new air, but it would be very hot air. Other than AC, there would be no way to cool down the house until 10 PM or so when it was finally cool outside.

I'll bet. :)
With regard to time spent sleeping:
Another thing I do is I have a table fan on the window sill above my bed. Well, if it were a real table fan, I would have had to make a bracket or little shelf. This is a fan from some 30's to 60's machinery, I think, and it has a 4 or 5 inch square base.
I've added an external speed control, so I make it slow enough that I can't hear it, and
I've added an external thermostat, so if gets cool enough during the night, outside and then in the room, the fan turns off so that I don't get too cold.
Another thing I had a problem with was that I alwasys needed a cover, a sheet or a blanket no matter how hot it was. When I learned to sleep with no pajamas and no cover, it was like it was 10 degrees cooler.

Meirman
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I think you got that worded a bit wrong, you say that the fans were worthwhile but the ridge vent was better. So your electric company should say that ridge vent are best but fans are better than no fans when ventillation is inadequate.
Art Todesco wrote:

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Actually, I think they are equivalent. Ridgevents are not easily put in after the fact; fans, electric or turbo, are. Either way, the AC load in my house was greatly reduced after adding the fans. If your power company makes a blanket statement that "Powered attic fans have been shown not to be cost effective in homes with air conditioning," people will not put them in and let the AC work harder. In cases where there is inadequate attic venting, the power company wins!
George E. Cawthon wrote:

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We are on the same page as far as power efficiency. I am just saying the power company is a regulated industry and would be shooting itself in the foot and subject to penalties to make a blanket statement like that. In any case, under current regulations, the power company probably has more incentives to tell customers how to conserve power than not.
Art Todesco wrote:

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Why don't you get a solar powered fan that will only run when the sun is strong and you won't have to worry about your electric bill. You only need one to draw out the hot air.
MH

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First you need to get the air in and if the only openings are the gable vents, you need power on the intake as well as the outlet to get a lot of flow. Second, solar powered is a great idea, but doesn't work out in practice for many applications. You might want to check the cost for a 400 W panel, which is the minium that you need. Then there is the problem that as it cools down, you want to exchange the hot air for the cool. Unfortunately that occurs at night.
MSH wrote:

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That's not completely true! An adequately vented attic will reduce the inside house temperature by about 10 degree. If an attic is alreay adequately vented, the fans won't be economical, but if it is not adequately vented and the fans make it so, then the fans will be economically justified. But, yes, ask your electric utility for the findings of experiments. In other words, don't rely on the opinion of some clerk than answers the phone.
jagerEd wrote:

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George,
Do you have any evidence that " ...but if it is not adequately vented and the fans make it so, then the fans will be economically justified?" As I said, I have seen reports of detailed studies showing they were not, so if there is newer and better evidence to the contrary, as opposed to someone just saying it's so, I'd like to see it.
BTW, my original comment about what the utility company would say is assuming that they have an energy conservation mandate from state and local authorities. That is, in many states utilities are legally constrained to NOT give out advice that will run up your bill. If not so constrained, and willing to deceive in order to improve their bottom line, they will love powered attic fans.
Ed

each
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Not in front of me, but I use to accumulate a bunch of energy conservation stuff. I've seen the 10 degree temp lowering (between adequate and inadequate ventilation) figure in Electric Utility pamphlets and in U.S. government publication. That stuff is somewhat old. The difference in power usage is so high (170 watts (fan) compared to 3600 watts (AC)) that if the fan only reduces AC running by only 1 hour per day it would be economically justified (operating costs only).
jagerEd wrote:

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In alt.home.repair on Tue, 15 Jul 2003 00:30:48 GMT "George E.

P&M
With those numbers, the fan can run 22 hours a day for the cost of one hour of AC time. In fact my fan at max runs from 9 in the morning until 10 at night. Usually hours less.
Probably even less yet, now that I went two shades lighter on my shingles.
I don't have good numbers on my AC because I don't use it enough to know. I have a 1400 foot home plus bsement, and it runs about an hour the first time it is turned on, after being off for a day or more, and I don't know how much it runs during the rest of the day. but I have a roof fan. I'm sure it woudl run quite a bit more if I didn't.
Possible Anti-my-position arguments: 1) The fan removes air at 120 or 140 degrees, but may replace it with air that is 90 degrees plus, if that is the temperature outdoors. The AC... it has the same problem because the part outside also has to deal with 90 degree air which lowers the efficiency of the AC the hotter it is out. 2) moving air is harder than moving the gas in a pipe/liquid in the AC.
I'm not a conspiracy guy, and I generally think that most people are basically good. But if they can hide 100 billion dollars of receipts at Ahold company, and manipulate California oil prices and Enron statements and Arthur Anderson, I'm sure they can come up with reasons to say a roof fan isn't good when it is.
I would want some source other than the electric company.
And I don't know enough formulas or enough math or have enough data to know for sure. But I'm still convinced using a fan is more efficient

Meirman
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: Hey all, : : I'm thinking of installing a couple electric duct booster fans onto my gable : vents to help remove the heat thats building up in the attic. One on each : end, one pulling air from the outside on one side of the house and : exhausting on the other side. Is there any drawbacks to doing this? Anything : I should be concerned with? : : Thanks all, : Brian
Installing two passive Turban (Turbine) Vents in my roof accomplished the same end for (LOTS!) less expense to purchase and operate.
We were seriously looking at the notion of putting in a couple of powered gable fans, but the hassle of mounting them, wiring them and cost of operating and maintaining them quickly ruled them out.
The two Turbans have lowered the summer-time attic temperature from the 150-160+ degree range down to the 110-degree range quite (summer-time ambient air) nicely. AC costs have dropped as well.
--
Steve
www.ApacheTrail.com/ww/
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As far as I've read, some towns feel that they are a fire hazard as they will pull a fire right up to your attic.
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: As far as I've read, some towns feel that they are a fire hazard as they : will pull a fire right up to your attic. : That same twisted "logic" would also apply to ridge vents, gable vents, and all other roof-mounted exhausts such as those for kitchen range hoods and bathroom exhaust fans.
After 8 years as a volunteer firefighter, I know it's standard procedure to chop a hole or three in an unvented roof to get the trapped heat and gases out so the fire can be fought.
--
Steve
www.ApacheTrail.com/ww/
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In alt.home.repair on Sun, 13 Jul 2003 08:56:12 -0700 "Steve"

What powers those things, to make them spin. Is it the wind, because I live in a valley and don't have much wind. If it is the rising hot air from the attic, what is the point of its spinning?

Meirman
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