Attic fans? One pulling in air, one pushing air out, same size.


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Old 03-01-24, 10:49 AM
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Attic fans? One pulling in air, one pushing air out, same size.

I live in Lubbock Texas where the humidity is always very low and it is always very hot. It's always very dry and most days in the summer, my attic is hell, reaching the top temperatures attics can. I have no heat release or ventilation of any kind at the moment.

So my question what is everyone's opinions on my plan of two identical automatic attic fans, my house is rectangular, I'm going to put one on either end, they are the same model and rated for the same square foot. my intention is to install one on either side of my home one pulling in air and the other pushing it out. It seems to me all of the cons I've read from people did not apply to me as I live in North Texas where it's basically a desert and hot all the time.

what I do know is my electricity bill for my AC is outrageous and it's constantly running and I assume that radiant heat alone with just basic insulation up there is bound to seep into my home. My HVAC system is not up there and I know I don't have any HVAC leaks, it seems to me that lowering that temperature would not only help the ducks stay cooler when delivering the cold air but also cool the entire house down. 180 is very hot very hot.

This is my first post here, please have patience!

Thanks for your help!
 
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Old 03-01-24, 11:50 AM
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Why do you feel you need 2 fans vs 1 fan and a vent?
 
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Old 03-01-24, 12:20 PM
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Not sure if this is responding to my intended comment person but here is the ans

Because if I only had one attic fan, there would be no air supply, and one of several issues it would cause is it would be more inclined to suck air from the living space. I came to this conclusion myself and then did a bunch of research and sure enough this is actually how you're supposed to do it you're supposed to have an intake fan and an exhaust fan. The whole point is to maintain the attic space as the same temperature as outside.
 
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Old 03-02-24, 08:06 AM
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Your plan seems reasonable. Have you considered adding ridge vents? What about adding more insulation to the floor of the attic?
 
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Old 03-02-24, 08:35 AM
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Unless both your fans are exactly matched (which they will never be) you will always be either pressurizing or inducing suction. Fluid dynamics then causes the issue you are trying to prevent. Not sure I've seen two many 2 fan solutions. I think the most common solution is one fan evacuating the air. The "air supply" is provided by a vent usually located as far from the fan as possible. Whether you use one and a vent or two fans, probably the more important thing to do is air seal your home as best you can to minimize your conditioned air being compromised.

I agree with you that 180 in the attic is excessive and probably contributes significantly to your AC bill. Adding additional insulation would (obviously) help also. Your first post states the AC is not in attic but then makes comments about the benefits of cooler ducts?
 
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Old 03-02-24, 10:03 AM
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IIWY (If I Were You) I'd go with passive cooling - a ridge vent and soffit vents, or perhaps a turbine / whilrlygig vent to simply bring in cooler outside air.
For my own setup, I do have a summer exhaust fan, but given that the window is a floor level in the attic,
For the attic of the original house, I've got a 'snorkel' of 18" flexi-duct up to the peak of the attic, and a sqare-to-route duct adapter beside the fan- so the fan pulls the hottest air from the peak of the attic. Also have the fan on light switch connected to a thermostat plug set for 120F.

As far as 'active cooling' I've got a fan in the attic of the addition setup to run at night, pulling cool evening air through the entire house. Works very well to vent the hot air out AND pre-cool the house during the summer (stone farmhouse in SE Pennsylvania, your thermal intertia, temperature and humidity may differ).

During the daytime, actively running a fan helps, but you need to have the exhaust fan on the sunny / hot side of the house, and then open a window on the shady / cool side of the house.
 
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Old 03-02-24, 12:35 PM
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Wutt? Go to reddit with your hostility.

I literally explained in my post that they were the exact same fans, and would be set to the exact same settings.
 
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Old 03-02-24, 12:37 PM
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That is correct. The HVAC is on the ground, level, the living space level, and the ducts go up into the attic, and then are distributed through the ceiling throughout the house.
 
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Old 03-02-24, 12:38 PM
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I have, however, besides the fact that statistically speaking attic fans with a supply and an exhaust when used correctly are far superior to every other method, but the house I live in was built in 1960. There are no Vince underneath the overhang. There's certainly not event at the peak of the roof I just wasn't on their mind in 1960.
today I started the first process which is getting the electrical system ready and made several junction boxes and hopefully by the time the bands arrive I'll have the electrical systems in place. Believe me I would not be crawling up there and doing all this unless I thought it would greatly improve the comfort and money situation.
 
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Old 03-02-24, 03:40 PM
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Rather than asking for opinions/input on your proposal (which is what you stated) it seems you are looking at affirmation that what you are doing is the most correct. I say this because less than 24 hours after inquiring from the board you've already started what you were asking about.

No two fans move the exact same amount of air, regardless of what settings they are at, a lot of variables affect air movement.

Good luck with your project, I hope it meets your expectations.
 
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Old 03-02-24, 09:46 PM
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You really need to work on your outlook, bro. Just reading your comment filled me with dread like I can't imagine being so pompous and rude to a complete stranger.
 
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Old 03-04-24, 01:51 PM
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Also, is that not what the purpose of asking someone's opinion/advice is meant to convey? Through my research and common sense. Those are the conclusions I came to, and I specifically said any input any opinions I wasn't asking for affirmation I was asking for advice. I think you would be better suited on a platform like Reddit.
 
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Old 03-04-24, 05:57 PM
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Have long used a dual mode seasonal setup to lower both heating and air condition cost and make for a more comfortable home.Use two fans in "push pull setup on New York area split level home.

In high level have roof fan:https://www.homedepot.com/p/Master-F...BLHT/302778687 Did not use built temperature control on fan in fan because it does not provide accurate control and ands is less effectrive. TETexas thread starter should be aware of this, Many do not operate fan until temperture is over 100F

Lower level has 16” window fan: https://www.homedepot.com/p/Lasko-16...6900/304988457

In summer both fans are activated by same room type thermostat in middle of lowerlevel with 1 F Delta set at 85F. In morning starts fans as sun heats attic roof and turns off fan as evening cools.it.

In winter, block off roof fan opening with hinged panel pulled by rope from lower level. Close lower level window with fan. Static attic air is insulating blanket between room ceiling insulation and inner roof.

This dual mode seasonal setup loweres both heating and air condition cost and make for a more comfortable home. In summer attic is only a couple of degrees above outside termperature. In winter is midway between in and outside temperature
 

Last edited by doughess; 03-04-24 at 07:37 PM.
 

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