Automatic attic ventilation fans - useful?

All,
You're a smart bunch of folk living in the same area with probably the same 120oFurnance of an attic like I have and I'm seeking advice ...
I'm thinking about installing some(2) attic ventilation fans in my roof that come on when the attic temperature reaches a particular limit - can anyone testify if they are financially worth it? I live in a modern (<5 years) 2-storey house and the upstairs A/C is naturally on quite often during the 90oF+ days.
Would attic ceiling fans help alleviate the A/C costs and also help keep my attic maybe 20 degrees cooler? Does anyone have experience of a before/after comparison?
Regards, PK
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I put one in my garage a couple of years ago because it was always too damn hot out there.It helped tremendously. I have the thermostat set high because it was running all the time. But with the slightly higher setting it only runs when it gets really hot out there. And it was relatively easy to do with basic skills and a saw.
Chris

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Don't put them near existing vents - will create a ventilation 'short circuit'. Or - replace the existing vents w/the new electric fans. Make sure you have plenty of eave/soffit 'ingress' ventilation - about 1sqft for every 8lf soffit. If you have high gables, you may do just as well replacing the wimpy original vents with larger or electric ones. This would be less likely to leak.
We had three installed as we were having re-roofing anyway. Can't report on cost savings yet, but couldn't see how we could lose, as some spaces were hell-hot, even with ridge and square hat-vents.
Ask at the home-lowes-depot about having a handy-roofer/electrician install them - I would guess about double a ceiling fan. We paid $100 each installed (by the roofer - except did the electric myself) for a unit that is probably $75 in the store (they would've had to flash-in normal vents anyway).
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I'm about to (any minute now - for the last 2 years) sheetrock my garage. It's detached; bought the house new with the studs showing in the garage. It's brick veneer with 4" studs, 9' plate, and hip composition roof. An 8' o/h door and a 16 footer.
Should I install insulation? Batts between the studs? Will this keep the heat out during the day, or hold it in at night?
How about a vapor barrier? Don't see as it will do any good as the inside humidity is roughly the same as outside - unless I make it into living space someday, which I won't.
I was thinking of putting some kind of reflective barrier or sheathing on the (obviously) inside of the rafters to kill some heat.
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It should already have a VB between bricks and studs. Batts between studs - really helps, makes it more of a living space.

Yes, also install electric wiring if you want

Both- put in an AC with Heater for $300 and your done.

Put Batts up there too
I converted a shead into an office, detached, came out really nice 10 by 12 thing

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LooknBlu wrote:

Insulation would be really handy if you're going to climate control your garage. You must really love your car.
--
Kelly Younger

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In spewed forth and said:

Look at it this way, it's a lot cheaper and easier to insulate now while there is no rock. A year or two from now you might want to make workshop or just have a place to take care of the honeydew list. Just cut a hole and put in a window unit and you'll be thanking yourself or saying what a smart SOB you were to have insulated when you did. I would think it would even help in resale value.
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I am going to do the same thing to my garage, clutter permiting, and I intend to install insulation. Unfaced would be the best as a vapor barrier would be useless as you said. I also installed and insulated garage door when I had to have my replaced 2 years ago. My neighbor went with the reflective barrier then sheetrock and he seems to be quite happy with the results.

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If the garage does not have AC in the summer and heat in the winter, then its counter productive.
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gurgled

Go up into the roof and make sure there is passive ventilation. Installing more soffits and that thin foam under roof channels is the cheapest. Putting in a ridge vent is not easy, but not hard...you just take your circular saw on both sides of the roof ridge and set it for maybe 1.5" inches and cut away a long line of shingles and MDF underlayment, install roof ridge and tuck the ridge's trailing edges under the shingles and then tack in place with galv short roof nails. Better yet, hire 2 meskins to do it and supervise.

I love rigid sprayed foam but its very expensive.
Regular old Corning pink insulation is your best bet, then put up some thick sheetrock. It's only a few cents more (maybe a total excess cost of about $40 more) for the whole area for thicker sheetrock. Will also help a lot with sound.

Yu're right about that. No vapor barriar unless it's a bathroom or washing machine/dryer unvented area.

A good hammer staple gun and a stack of light blue sheathing and one person maybe to help hold it in place while your tack and you can have it done in about 1/2 hour!
But at the base of each sheathing should be a soffit, and at the top of the sheathing should be ridge vent outlet.
HTH
--
---Mapanari---


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No - electric fan cost are too high. You can get passive ones put in much better, no electric cost(done in newer homes).

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Any recommendations for an attic fan that would work well for an attached garage with a very low pitched rock roof that currently has no ventilation? 1959 Ranch house in Ventura, CA (near Santa Barbara) - near the beach with mild weather in all seasons. Hottest it ever really gets here is high 80's, but since garage is not vented, it bakes inside in summer. A concern would be that the unit wouldn't allow rain in during a heavier storm given howw flat the roof is. (when it does rain for our 5 or so days a year)
--
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A ridge vent may be the safest (leak-wise) and easiest to install. If you don't have gables (a hip roof), that and the passive-turbine or 'hat' vent are about the only other options. A ridge vent can yeild a lot of total square inches and excellent coverage (one end to the other and all-points-in-between).
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Very useful in Ohio where it will get below 60 at night. Useless in Houston.
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Rbert M. wrote:

FWIW -
I live in Austin, and I see some benefit from an attic ventilation fan (as opposed to a "whole house" attic fan) -- before installing it, my attic was going well above 120 degrees (the highest the thermometer I put up there would read); now I can generally hold it to about 100 degrees even on hot, sunny days. I've read attics here can reach 150 degrees, and I believe it. Before, you could actually feel heat emanating from the ceiling; now you don't -- that _has_ to mean my AC runs less. Of course, the fan consumes some power, but it is only about 5 percent (probably less, actually*) of what the AC uses when it is running, so I think I'm better off net, although I don't yet, and may never, have the data to prove it.
I hope my roof lasts longer, too, as a result of the lower temps.
One can get solar powered fans, which might improve the economics, although they're fairly expensive so amortization might take too long.
*The information I have on power consumption of the various devices comes from the plates attached to them and stuff I've been able to glean from the Internet, so might not (probably doesn't) reflect their actual usage in a normal duty cycle. That said, it gives some idea of the magnitudes involved:
Attic ventilation fan: 300 watts AC: 29.1 amps at 230 volts, or 6693 watts (excluding the fan on the furnace, which is probably another couple of hundred watts, but I can't see the plate on it)
I'd be very interested to hear further comments on this, because I've been putting a lot of effort into trying to hold my electric bills down, and AC load is key to that.
I've concluded the "whirlybird" type ventilators are pretty ineffective in Texas.
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wrote:

Folks without an economic axe to grind (i.e. they aren't selling anything) recommend roof ridge vents for Houston, with Soffet vents all around.
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Would the people in alt.home.repair please remove the other crossposted newsgroups from this thread before they answer it, and please note the person that started this crossposted thread.
Ken Leander (listening on austin.general)

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wrote:

Congradulations, Robert. Ya got one right.
Mike Smith
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