Just curious whether an attic fan is apropos here

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Here is one of my five attics:
https://c2.staticflickr.com/4/3895/14893084977_8c670115cf_b.jpg
Would an attic fan, of some sort, be feasible in this location?
https://c2.staticflickr.com/6/5582/15079282762_8959e28b99_b.jpg
The house has AC, and three floors, and it's insulated with the loose stuff, at least anywhere where I can 'see' the rafters.
It's California. Northern. So, it's a pretty mild climate, but, it's as hot as blazes in these attics, so, I was just wondering if it's better to run the home heating system fans, or, put an attic fan in to cool the house down, without running the A/C?
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On Saturday, August 30, 2014 1:59:52 AM UTC-4, Danny D. wrote:

Are we talking about an attic fan or a whole house fan? Attic fan is to cool just the attic. Whole house fan sits in the upstairs ceiling, between the living space and attic and draws air into the house through open windows, pushes it out via attic vents.
That tiny opening is too small for an attic fan. I'm not a big fan of attic fans. I think most building science folks recommend ridge vents and soffit vents as the best overall solution today. Ridge vent is easy to install on most roofs, soffit vents can usually be added too. If you want a power fan in that attic, easiest thing would be to either put one in a similar gable vent on the other end of the attic, or put in a roof mount one on the other end. That way air will come in via the one in the pic, move through the attic, out the other end.
For a whole house fan, you need sufficient attic venting to carry the volume of air. How well they work, how much you can use one vs AC depends on the climate and your usage model.
I see them as most useful for situations like where you've been away all day, the AC has been off, house is hot, it's night, cooler outside now, you come home and want to cool it down. It also doesn't work well in humid climates, but you're OK there.
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Danny D. wrote:

You are going to receive differing opinions about the value of an attic fan. Some maintain that the cost of running the attic fan is offset by the cost savings of running an air conditioner less and therefore a wash. They see it as useless to keep the attic cool if you spend the same amount on electricity.
I live in a southern state where the outside temperature often reaches 100 degrees in the summer months. My furnaces are in the attic, and the evaporator coils for the AC are of course inside those furnaces. If the outside temperature reaches 100, you can imagine what the temperature in the attic reaches. I have a gable roof like you do, with vents in the eaves. I have two gable fans that are set to turn on at about 95 degrees so that when the AC is running the temperature around the furnaces is as low as it can be. My theory is, that not doing so would be like having the evaporator coils in an oven.
The bottom line is that although I do consume electricity to run the fans, my electricity bill is much lower than my neighbors. I also have programmable thermostats, so that also helps. I will finish with the fact that I placed a thermometer in the attic once to see how high the temperature would go without the fans on, and it exceeded 120 degrees. That was as high as my thermometer would read.
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Danny,
The 1st pic shows an attic with a window. The 2 nd pic looks like a soffit vent. Is there any other ventilation? A fan in that window might be good ventilation. Does rain normally blow in that direction? A good project for when the weather gets a little cooler. You have 5 attics? You mean unconnected spaces? Sounds like 5 attic fans.
Dave M
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On 08/30/2014 12:59 AM, Danny D. wrote:

It won't hurt to put in an attic fan but it will not do much to cool down your house, on a hot day you will still need your AC.
I'd be more concerned with the support beams, they certainly do not look at all right.
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Danny D. wrote:

You are going to receive differing opinions about the value of an attic fan. Some maintain that the cost of running the attic fan is offset by the cost savings of running an air conditioner less and therefore a wash. They see it as useless to keep the attic cool if you spend the same amount on electricity.
I live in a southern state where the outside temperature often reaches 100 degrees in the summer months. My furnaces are in the attic, and the evaporator coils for the AC are of course inside those furnaces. If the outside temperature reaches 100, you can imagine what the temperature in the attic reaches. I have a gable roof like you do, with vents in the eaves. I have two gable fans that are set to turn on at about 95 degrees so that when the AC is running the temperature around the furnaces is as low as it can be. My theory is, that not doing so would be like having the evaporator coils in an oven.
The bottom line is that although I do consume electricity to run the fans, my electricity bill is much lower than my neighbors. I also have programmable thermostats, so that also helps. I will finish with the fact that I placed a thermometer in the attic once to see how high the temperature would go without the fans on, and it exceeded 120 degrees. That was as high as my thermometer would read.
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On 8/30/2014 1:59 AM, Danny D. wrote:

Trader's response is spot on. I use our whole house fan about 15 to 20 nights a year and AC the other more humid days. I do like it at other times if I want to clear the air quickly from cooking or anything else. You don't want to suck in 95 degree humid air if the house is 70 degrees from the night before. Use it wisely.
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On Sat, 30 Aug 2014 05:59:52 +0000 (UTC), "Danny D."

No Put the fan in the gable vent. Force a draft across the attic to remove the accumulated heat brfore it can "soak" into the conditioned space.

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trader_4 wrote, on Sat, 30 Aug 2014 04:27:21 -0700:

I'm not sure. I have fans in the ceilings. I think I'm talking about just cooling the attic, which, is admittedly steaming hot most of the time. I was guessing cooling the attic would also cool the house. No?

OK. Good point. I've never seen an attic fan, so I don't know the size of the opening.

Pun intended?

It is often cooler at night here ...
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On Saturday, August 30, 2014 11:48:33 PM UTC-4, Danny D. wrote:

What kind of fans are these?

Lowering the attic temp will help. The question is how much you can reasonable lower it via the possible methods and how much actual benefit that will have in the living space. The attic is insulated and that is the primary means of preventing heat transfer. I notice you have blown-in insulation about equal to the joists. In some spots, it's a lot less. Adding more insulation would probably have a bigger impact year round than adding a fan.

Powered attic fans come in two main types. One is a roof mounted mushroom type. The other is a gable type. Those can be had with their own entire gable vent, ie louvers that open, etc or you can get just a fan that goes behind an existing gable vent. The latter could go behind your gable and blow air outside. I have one like that.
But as I said, I've come to believe that a ridge vent is the better solution.
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David L. Martel wrote, on Sat, 30 Aug 2014 08:33:01 -0400:

Both pictures were taken from essentially the same standing position in one of my five attics. All the attics are essentially the same, just disconnected from each other.
These "windows" are the only ventilation that I know of in the attics.
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Oren wrote, on Sat, 30 Aug 2014 06:19:24 -0700:

I wasn't sure. I do like the pictures because they give me an idea of what size these fans look like, and how they're mounted. Thanks.

Ooooh. Nice. Very nice. I have more sun than most people, being on a mountain above the clouds, so, that's kind'a nice having the solar fan. Problem is the roof itself is tile, so, I'd have to figure out how the panels go up there...
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On Saturday, August 30, 2014 11:53:17 PM UTC-4, Danny D. wrote:

The solar panels take care of themselves. They are mounted on the top of cover of the fan. It goes in just like any AC powered roof fan would. What I'd be concerned about is the CFM of that fan versus the CFM of similar AC fans, is it adequate, how long will it last versus AC fan, costs, etc.
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Ed Pawlowski wrote, on Sat, 30 Aug 2014 10:59:45 -0400:

This is a good point. It's generally 10 degrees (or so) cooler at dawn and dusk than during the day, but during the day, it's hotter outside than inside (summer).
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Bob F wrote, on Sat, 30 Aug 2014 08:01:16 -0700:

Oh. I hadn't realized that until you just said it. There are five attics, so, it would take five of them then. Yuck.

I had to look at the picture to see what you're talking about. It was just the sun shining in given the contrast between the dark attic and the light outside.
Yes. They all have a rectangular hole, with a screen on it. And that's it. There is no glass window.
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On Saturday, August 30, 2014 11:56:56 PM UTC-4, Danny D. wrote:

It wouldn't take five whole house fans. The primary purpose of a whole house fan is to cool the living space, not the attic. In fact, most of them probably aren't even running during the hot portions of the day. They typically get turned on at night, when it's cooler outside.
So, you could put one in, using one of the attics. That one attic would need sufficient venting to handle the air. You'd typically install it over an upstairs hallway so it can pull air from the whole house.
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Oren wrote, on Sat, 30 Aug 2014 15:05:30 -0700:

Yes. I didn't know what a "soffit" was, offhand.
Googling, I see it's the "underside of an architectural structure such as an arch, a balcony, or overhanging eaves.".
Those small rectangular "soffit vents" are all over the place in each of the attics.
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trader_4 wrote, on Sun, 31 Aug 2014 04:29:33 -0700:

Your typical five bladed fans, about 5 or 6 feet in diameter, way up high in the ceiling (about 20 feet up or so).
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trader_4 wrote, on Sun, 31 Aug 2014 04:29:33 -0700:

That's why I had asked. I'm just curious if it's a good idea or not, given that it would be work to do it. Luckily, there is electricity in the attics, as each have a light bulb at least.

The blown in stuff is all that I see. There are boards on some of the attics, but usually only in the center where we can store some stuff.
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trader_4 wrote, on Sun, 31 Aug 2014 04:19:07 -0700:

Oh. OK. That would go into the attic that I provided the pictures of since it's over some of the bedrooms.
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