attic fan

[nightvision]

Hi all,
I'm considering adding an attic fan to cool off the attic space during the hot summer months. We get well above 100 degree ambient temp for weeks at a time. August is the worst month with temps sometimes at 110 degrees. I recall one August we were not home for three days and the AC was off. When we came back the temp in the house was 92 degrees. I know that the attic space can get to 120-130 degrees at times and I'm curious to know if the attic fan can bring the temp down close to abient air temp say 100 degree or at least close to it. I read that heat in the attic can transfer down to the house cealing and into the living space. What do you guys think?

 

[LubeDude]

Re: attic fan

An Attic fan will do what you want it to do, but only if you have adequate air coming in also. There is a chance that all of your roof vents if they have been there awhile are clogged with dust and spiderwebs. You might do well to add an open air vent to the oposite end of the house with a screen to make sure you have a good flow. Make sure you get a fan that will cover the size of your attic space. Most of them have thermostats that can be set at different temps. In you situation, they would likely be on all the time durring the summer months.

 

[flashback]

Re: attic fan

The vent fans will work if placed in the right location and if the soffit has enough ventilators.. IMHO though, a ridge vent with continuous soffit vents work just as good and don't use any electricity...

 

[Bob_VT]

Re: attic fan

I have a simple vent fan in the roof that is controled by a thermostat switch. Does a great job and is all automatic.

 

[tommays]

Re: attic fan

I have a full ridge vent with plenty of sofit vents to allow air flow

It still gets hot enough to hit the stat on the atic fan and pull more air across to keep the AC air handler cool


Tommays

 

[i386]

Re: attic fan

I've seen the solar ones going for around $350 I think. I have full ridge vents too but my attic still get's in the 115+ temp range in the summer. I've been thinking about putting in the solar kind. If not for the electricity savings, it saves me (or the electrician) from having to run power to it.

 

[QC]

Re: attic fan

Do you have a basement? My mom had an attic fan installed in her house in SoCal. This one was actually mounted into the top floor's ceiling/attic floor. Probably 4ft. in diameter. Had slats over the intake grates that opened when you cranked it up. It also had a rheostat like dimmer switch thing to manually vary the speed. Anyway, with the cool air in the basement, and good venting out of the attic, I swear it brought the house down below ambient. I loved that thing, especially the switch as you could sit there and rev it up and down like any good propeller type thing

 

[Limited-Time]

Re: attic fan

I have a full ridge vent with plenty of sofit vents to allow air flow

It still gets hot enough to hit the stat on the attic fan and pull more air across to keep the AC air handler cool


Tommays

Ditto here. Drawing the heated air out, and cooler air in will make a huge difference, especially if the attic insulation ain't "up to snuff" as they say.

 

[i386]

Re: attic fan

Do you have a basement? My mom had an attic fan installed in her house in SoCal. This one was actually mounted into the top floor's ceiling/attic floor. Probably 4ft. in diameter. Had slats over the intake grates that opened when you cranked it up. It also had a rheostat like dimmer switch thing to manually vary the speed. Anyway, with the cool air in the basement, and good venting out of the attic, I swear it brought the house down below ambient. I loved that thing, especially the switch as you could sit there and rev it up and down like any good propeller type thing

I have one of those too. A word of caution about those as some others may bear witness too. It's tempting to run it at night or after a rain as it does cool the house really well. The downside is the moist air will mildew all your nice leather shoes, belts, jackets in the closet. At least that's the case here. We mainly use ours to de-stink/smoke the house if something gets burned in the kitchen.

 

[Mark42]

Re: attic fan

I have installed the "whole house" type fan that is mounted in the ceiling. It draws from the house, and blows into the attic. It works very well, one fan vents both the house and attic. They are very high CFM fans, and need an additional vent mounted in an end gable. The end gable vent is usually a spring loaded vent that opens when the pressure rises in the attic.

They are not very expensive, so get the best model you can. Multiple speed, low noise, low energy usage motor.

 

[2broke4this]

Re: attic fan

This may sound silly, but if your attic isn't vented well, and you crank that fan up, you may cause yourself some serious trouble. Think about this for a minute... if your windows are all closed (not saying that this is necessarily the case)... and you have a gas hot water heater that vents by stack effect (not direct vent)... which happens all the time here in Indiana.... you run the risk of backdraft down the vent and flooding the house with CO.

I'm not saying that this is DEFINITELY would happen, but it's something to look into... Let's say you've got that huge fan on a thermostat... the windows are all closed.. and you come home at the end of a hot day and the fan has been running all day, sucking the exhaust from the hot water heater into the house... that doesn't sound good to me!

Again, I'm not saying that attic fans are going to kill you, or not to install one, I'm just saying to use some caution and make sure your water heater (furnace) is directly vented and make sure you have a good CO detector if you DO install one! The gasses you suck into the house may not kill you, but they won't do you any favors, and I'm getting pretty attached to this forum and its members. Feel free to call me crazy, but I'd check the CO levels in your house while that fan is running... especially if it's running with the house all closed up!

-Carl

 

[Mark42]

Re: attic fan

Carl makes a valid point. A whole house fan usually requires that windows be open when in use. I once turned on the fan, forgot to open a window, got in the shower, and the fan sucked the exhaust from the oil fired water heater back down the chimney and into the basement. I only discovered this when later I went to the basement and it was full of white smoke.

So if you get a whole house fan, make sure you use it properly.

But you gotta admit nothing will vent your house like a whole house fan on max. Like a wind tunnel!

 

[QC]

Re: attic fan

Yeah, these "whole house" deals are what I was talking about. In SoCal our basements (only really old houses actually have them) are all vented with open screens directly to the outside, so the fan ultimately sucks air in from the cool basement and adjoining gardens etc. I am thinking that a basement like this would be really stupid where it gets cold and/or floods . . .

Yes, you must properly vent the attic. If they're right, they're awesome.

 

[GlasstronJim]

Re: attic fan

Yes, we have a whole house fan to. You always open windows and shut the damper down on the fireplace or it will suck the soot right in. They are a very powerful fan, it will drop the temp in ours 20 degrees in 5 minutes.

 

[rickdb1boat]

Re: attic fan

I like ours, but it's an older one with only a single speed motor. So it's all or nothing. I really need to update to a 2 speed quieter model, as this one will drive you crazy.

 

[Solittle]

Re: attic fan

Don't stop with the attic fan. Anything you can do to get the hot air out of the attic will bring benefit to the lower part of the house. We have a thermostatically controlled attic fan, soffit vents all around the house, two turbines and extra insulation in the attic.

 

[bruceb58]

Re: attic fan

Whole house fan is the way to go. In SoCal the nights cool off to a point that we can get the temp inside the house down to a very comfortable level without A/C. All of out neighbors have the A/C going all night long trying to cool their heat soaked houses.

One thing you have to make sure of is that you have enough vent area.