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Whole-house fan
Old 03-16-2012, 09:54 AM   #1
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Whole-house fan

I'm thinking of installing a fan in our attic space to draw air into the house from a cooler outside, and exhaust hot air up through a louver in the upstairs hall ceiling and out a louver in the gable end wall of the attic. I'm thinking I would want to hang the fan on spring isolators from the roof rafters (to minimize vibration and noise), and have a ducted connection between the ceiling and gable louvers.

Anyone have experience or knowledge of such an installation? What should I do or not do? And what type and size fan should I be looking at (house is about 2000sf with 8' ceilings).
Thanks......
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Old 03-16-2012, 10:22 AM   #2
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While living in NY I had installed a whole house fan. We were living in a split level and had the unit in the ceiling of the upstairs foyer near the bedrooms. I loved having the unit and it brought in some cool air during certain times of the year. Still didn't replace AC when it got hot.

As long as I didn't turn it up on high it was very quiet. You could shut the doors of the rooms you didn't want to draw air through and I would recommend the unit to you.
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Old 03-16-2012, 10:34 AM   #3
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Just remember that it brings in the outside air (and particulates) through your windows. In the SE US, we shy away from using it in the Spring very much because it coats the interior of the house in pollen. In the Fall it is golden and keeps the compressor from running as much as it would on those warm autumn days.
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Old 03-16-2012, 10:52 AM   #4
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bobot,

Can't see where you live.

Friends had one in an old house with high ceilings in Tampa, FL. It was a huge, ancient multi-blade wood fan above louvers in the ceiling. Because the ceilings were high and the speed low, very little noise.

It did bring dust in from outside. Probably the biggest problem.

In our houses, we have always installed gable fans on thermostats and vents in the eaves. They keep the attic cool. We then open the windows in the house as needed, which limits the dirt that comes in.
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Old 03-16-2012, 11:02 AM   #5
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I believe there are other thoughts on this system vs an exhaust fan for the attic hot air. I think they can be set up to run based on temperature inside the house. The fan is installed behind a louvered panel that closes when the fan stops. I've never had one but would think this might be better than drawing hot air and pollutants into the attic. Also, I've never researched this subject online.
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Old 03-16-2012, 11:52 AM   #6
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Do you have a forced-air furnace now? If so, a fresh-air intake may be able to be rigged up including a motorized damper and control. That would draw fresh outside air and deliver it through through the existing duct system.
As Jonnie36 mentions, attic fans mounted in a gable end are the first choice for most houses. This dumps the attic heat and helps the house temp as it does.

Also, you may post up on "heating help" a board of hvac pros who are very generous with tips and caveats! [Beware they will encourage you to get a pro, and can be quite acerbic]
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Old 03-16-2012, 12:08 PM   #7
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In our houses, we have always installed gable fans on thermostats and vents in the eaves. They keep the attic cool. We then open the windows in the house as needed, which limits the dirt that comes in.
+1 This is the standard set-up in New Orleans. These fans are absolutely necessary for the AC to be effective. Otherwise, the AC is struggling to cool the ferociously hot attic air and the result is still pretty hot.

I had my old non-working one replaced with a better version, and rewiring done for it in 2010. This involved an electrician, a roofer, and a handyman and wasn't cheap. However, my AC works much better now and it was worth every penny. The fan is on a thermostat which is set pretty high. I don't remember exactly where it is set; 110F, maybe. When the weather is hot, sometimes I can hear it switching on when I walk down my hallway.

When the weather is nice, I open all the doors and windows and air out the house. Otherwise I don't....
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Old 03-16-2012, 12:13 PM   #8
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W2R, I think you are talking about the wrong type of van. Your's is a roof fan to keep the attic cool. The OP is talking about a whole house fan.
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Old 03-16-2012, 12:37 PM   #9
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We had exactly the kind of thing you're talking about in a previous house. House was built in the 1930s, about 2,000 sf. The louvers were in the upstairs hallway ceiling (outside the bedrooms), and sucked air into the attic, where the fan (about 12 inch diameter blades IIRC) was mounted in a gable. It was controlled by a simple switch in the kitchen, but that could easily have been hooked to a thermostat.

It worked very well during certain parts of the year, and probably saved a little on a/c costs during those weeks, but if the outside temp was much above 80°F then we needed to shut it off and go with the a/c.

In another climate zone, it might have proved a better option, but in southern Ohio it was only of limited utility.
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Old 03-16-2012, 01:48 PM   #10
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Just make sure you install a fire safety thermostat, just in case there is a fire in the house it shuts down the fan,when it detects excessive heat.
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Old 03-16-2012, 02:04 PM   #11
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The quietest and most durable fans will have a large fan area and likely a motor that drives the fan using a belt.

In some parts of the country whole-house fans can be useful. Remember that comfort is a function of both temperature and humidity, and it's unlikely you'll be comfortable if you are bringing in cool air that is saturated with moisture (typical in the mornings in much of the country much of the time).
When you run the A/C it not only cools the air but removes moisture, which is usually a plus.

The fans are probably most useful where daily temps have a wide swing and where the humidity is low. I don't like the feeling of a breezy house, so I wouldn't install one. But, I don't care for ceiling fans, either, and I know I'm in the minority. Bld999's suggestion of using an external air inlet and your HVAC ducts to distribute the incoming air throughout the house is a good idea (reduces drafts, more even temperatures), and in some situations it might even be possible to have this air go through your regular furnace filter to remove some of the pollen.

If you are doing this to save money, compute the payback period. It would probably be long in most areas (due to the fairly limited number of hours that outside temp/humidity are more agreeable than inside temp/humidity). The same money spent on attic insulation would boost comfort and reduce utility bills winter and summer, require no maintenance, use no electricity, and reduce noise rather than increase it.

It's another "thing" and requires manual intervention (turn off the HVAC, open windows, turn on the fan).

Also, you'll be depressurizing your building envelope when the whole-house fan is turned on. If you've got enough incoming air it may not be a significant issue, but if you're depending on the gaps and holes of the house it could be a different story. The depressurization may cause problems for combustion appliances (furnace, gas/oil clothes dryer, gas water heater, etc) and result in CO entering your home. It probably won't be a safety factor as long as the fan is pulling a lot of fresh air into the home, but if the fan is on low it could cause an indoor air quality problem in some circumstances.

The hillbilly alternative: A box fan propped up in the window of a little-used room to blow air out, and other windows opened in selected rooms of the house. 20 bucks, and if it proves its worth you could go with a more permanent arrangement.
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Old 03-16-2012, 02:20 PM   #12
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Originally Posted by braumeister View Post
We had exactly the kind of thing you're talking about in a previous house. House was built in the 1930s, about 2,000 sf. The louvers were in the upstairs hallway ceiling (outside the bedrooms), and sucked air into the attic, where the fan (about 12 inch diameter blades IIRC) was mounted in a gable. It was controlled by a simple switch in the kitchen, but that could easily have been hooked to a thermostat.
I don't think you'd want it hooked to a thermostat, unless this is a lot different from what I had in a previous house. My fan was very strong, and if you didn't have windows open, I was warned that the air pressure in the house would get too low. Thus, you wanted it manual, so you could make sure the windows were open when you turned it on.

Mine was also pretty loud. A lot of times I would just leave the A/C off when I was at work, and if I came home late enough that it had cooled down some, I'd crank up the house fan for 15 minutes. Even if it was warmer than I wanted it, it would get the house temp down somewhat so that the A/C didn't have to work as long, and on cooler days it was all I needed.
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Old 03-16-2012, 02:24 PM   #13
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We had a belt driven whole house fan in our old house in Chicago, it worked really well when it was hot and humid and then the temp would drop 20+ degrees after rain. Turn on the house fan and in minutes the house is cooled off. New buyers were stunned how low our electric use was in the summers, they only believed us when we showed our electric bills to them. We always tried to draw in fresh air and this fan is great on days when AC is barely needed. Certain parts of the house felt like being in a wind tunnel. I did install a power roof vent to help move out hot attic air about 18 yrs ago. My house fan was from the 1940's and only had 1 speed, high. New units I've seen have variable or multi speeds that would limit/reduce the noise these things put out. I can tell you we got used to the noise after a little while.
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Old 03-16-2012, 03:10 PM   #14
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I don't think you'd want it hooked to a thermostat, unless this is a lot different from what I had in a previous house. My fan was very strong, and if you didn't have windows open, I was warned that the air pressure in the house would get too low. Thus, you wanted it manual, so you could make sure the windows were open when you turned it on.

Mine was also pretty loud. A lot of times I would just leave the A/C off when I was at work, and if I came home late enough that it had cooled down some, I'd crank up the house fan for 15 minutes. Even if it was warmer than I wanted it, it would get the house temp down somewhat so that the A/C didn't have to work as long, and on cooler days it was all I needed.
That's a good point; you're absolutely right. I guess that's why it only had a wall switch to control it.
Please disregard everything I've said since "Good morning."

Ours, now that I think of it a little more, was more like 24 inches in diameter, and belt-driven from an offset-mounted motor, like samclem mentioned. It wasn't that loud, because we had plenty of insulation in the floor of the attic, but it certainly had a powerful draw.
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Old 03-16-2012, 04:51 PM   #15
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I put a whole house fan in my first house. Second floor ceiling at the top of the stairs. I would open the basement windows and turn on the fan and it would draw air from the basement and cool the whole house down. It was noisy since I mounted mine directly to the ceiling joists. I only ran it for about an hour in the evenings. Mine vented through the soffitt vents, but gable vents would work also. I don't think you need to run duct from the fan to the gable vent. It should vent fine as long as the vents are clear and you have as much open window cross-sectional area as you have vent area.
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Old 03-16-2012, 05:22 PM   #16
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Lots of good info & thoughts here, thanks to all who have posted - I knew I was asking the right group!

We're in the mid-atlantic, and humidity and pollen are real considerations. I guess we would only run it during the swing seasons, when we just want to get the temp down at night without running the heat pump; we're fresh air freaks & sleep with the windows open if possible.

Good point about a cut-off tied into heat/smoke detection; hadn't thought of that one.

A HVAC guy is coming out Monday to have a look & make a proposal; I'll let you know what transpires.
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Old 03-16-2012, 08:03 PM   #17
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I put mine on a few layers of that closed cell foam that's designed to go under the exterior walls in new construction. The noise from vibrations is nothing compared to the whoosh of the air, hehe. It's 30 inches or so, offset motor and belt. The shutter is a separate purchase, but made for it. The shutter isn't perfect, and you will loose a lot of heat in the winter unless you do something about it. I have some 1/2 foam board the size of the shutter with Velcro on the entire perimeter.

Pollen and humidity keep us from using it much. The evenings are drier than the mornings, so we use it more then. It's on a timer that can be set from 30 minutes to 4 Hours. So hot days cool nights, we set it for four hours, and the next day the a/c kicks on at least a couple of hours later than the neighbors.

But honstly, for as few days as we use it, I might not put one in the next place. North Carolina in the piedmont., btw. The cheap side of me likes it, even though there are very few days it makes sense to use.
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Old 03-16-2012, 08:51 PM   #18
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I live in the deep South USA. The house I was brought up in and the first house I bought had whole house fans. These fans were mounted in the ceiling and drew outside air into the house through windows and doors and exhausted the air through the attic. Personally, I don't want another one. When the ambient temperature outside is 98 and very humid, what's the point in bringing it inside? Also, these whole house fans were very powerful, you would not want to turn them on with the windows and doors shut. Although, we did think they were great in the days before AC.

When we did our last roof job, we removed the electric powered attic vents and replaced them with wind powered turbine vents. Since the attic was so hot, the electric motors in the electic powered vents had a rather short life.
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Old 03-16-2012, 10:06 PM   #19
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Here in Colorado, the whole-house fan I installed years ago is all we need to live comfortably during hotter parts of the summer. Keep the windows closed during the day, then open them at night and turn on the fan. But our climate is the key: low humidity and cool nighttime temperatures.
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Old 03-16-2012, 10:14 PM   #20
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While living in NY I had installed a whole house fan. We were living in a split level and had the unit in the ceiling of the upstairs foyer near the bedrooms. I loved having the unit and it brought in some cool air during certain times of the year. Still didn't replace AC when it got hot.

As long as I didn't turn it up on high it was very quiet. You could shut the doors of the rooms you didn't want to draw air through and I would recommend the unit to you.
Pretty much my feelings except substitute Kansas for New York.
Get a quality unit and one that can be controlled by a rheostat and you'll be able to crank it down to barely a whisper.
Everywhere else we have lived has been/is much too humid to consider sucking outside air in.
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