# Attic Fans-Are they worth it?



## cnet24 (Jul 14, 2017)

I have an attic fan mounted to our roof that appears to not be functional. I've read conflicting reports if it is worth replacing or not. I do know in new construction they are not used, however my home was built in 1995 and does not have the same "rigor" of insulation vs. today's homes. Is it worth replacing?


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## Powhatan (Dec 15, 2017)

If your roof was not built with passive ventilation, then yes I'd replace the fan so hot air has a way to escape and cool your house.


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## cnet24 (Jul 14, 2017)

@Powhatan passive ventilation meaning ridge venting?


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## Powhatan (Dec 15, 2017)

cnet24 said:


> @Powhatan passive ventilation meaning ridge venting?


@cnet24 mostly yes - ridge venting passive cooling, but there are also vent caps that are considered passive.

My last older home pre-1995'ish roof was built with a single motor attic fan for cooling. When I replaced the roof singles, they cut out parts of the roof ridge to create passive venting - house was much cooler aftewards.


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## ionicatoms (Mar 8, 2020)

https://blog.directenergy.com/does-my-home-need-attic-ventilation-fans/


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## cnet24 (Jul 14, 2017)

Thanks @Powhatan and @ionicatoms for your input so far. I've been reading on passive ventilation and the blog, and I thought I would share pictures of my actual situations to get your take. I do have PVC lines running through the house and venting to the roof, but not sure if this is the passive venting noted above.

Pictures of roof line- the broken attic fan is at the very top of the second picture. You can also see the ridge venting on the roof line:




Other venting boots on the roof. The three taller boots I believe are venting from two furnaces and a hot water heater.





Examples of soffit venting and spacing:



From the first picture, an example of what is tied to the shorter boot from inside the attic- if I have passive ventilation, this is my best guess of where it would be:


Thanks for reading. I got a quote for $600 to fix the fan and can't determine if it is worth it.


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## Powhatan (Dec 15, 2017)

The piping shown on your roof is either plumbing or heat (stove, water heater) venting. The venting on the sides are bathroom humidity fan vents. Your drier vent is probably closer to the ground, unless your wash/dryer are upstairs.

Kinda hard to tell from your pics, you might have a roof ridge vent, there are different install methods, but with an obvious cut out section at the ridge top as shown in the below website.

https://www.cjenkinsconstruction.com/roofing-services/photo-gallery/25454-album-sawgrass-manor-dr-ridge-vent.html#ad-image-0

It's possible your attic vent fan provides additional cooling when a certain temp is obtained. IMO since your house build came with a roof vent fan I'd replace the failed unit.


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## cnet24 (Jul 14, 2017)

Powhatan said:


> The piping shown on your roof is either plumbing or heat (stove, water heater) venting. The venting on the sides are bathroom humidity fan vents. Your drier vent is probably closer to the ground, unless your wash/dryer are upstairs.
> 
> Kinda hard to tell from your pics, you might have a roof ridge vent, there are different install methods, but with an obvious cut out section at the ridge top as shown in the below website.
> 
> ...


Thanks!


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## Powhatan (Dec 15, 2017)

@cnet24 whoever replaces your attic vent fan, have them make sure there's power and the motor enage/disengage (sensor) mechanism works.  At my last house, the previous homeowner had an unlicensed DIY electrician tap into the attic fan power line and used it for another purpose.


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## FlowRider (Apr 7, 2019)

Looking at your pictures, your roof was designed to have an attic vent fan operational to ventilate your attic.

You have very limited passive ventilation when looking at your soffits and soffit vents in place.

Without a powered ventilation fan to move the air and induce ventilation of heated air to exit the attic, your attic will be very hot in summer and will drive up your air conditioning costs, and lower the life expectancy on your roofing shingles. You have no insulation on your roof sheathing, just OSB.

The $600 you spend will be paid back pretty quickly, in terms of air conditioning and roofing costs.


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## cnet24 (Jul 14, 2017)

Powhatan said:


> @cnet24 whoever replaces your attic vent fan, have them make sure there's power and the motor enage/disengage (sensor) mechanism works.  At my last house, the previous homeowner had an unlicensed DIY electrician tap into the attic fan power line and used it for another purpose.


As far as I can tell, it is on its own power line. I'll be sure to double check!



FlowRider said:


> Looking at your pictures, your roof was designed to have an attic vent fan operational to ventilate your attic.
> 
> You have very limited passive ventilation when looking at your soffits and soffit vents in place.
> 
> ...


Welp, not something I want to hear after spending $10K on a new 2.5 ton unit and upgrading my blow-insulation. The insulation company didn't mention anything related to insulation missing under the roof sheathing. For my understanding, what would you use for this application?

I'm beginning to think the insulation guy skipped this house when building. To give you an idea of how frustrated I am, we recently replaced the fireplace tiles which gave me access to look behind the exterior walls. Not one single insulation batt in the entire cavity (2 story fireplace). Not to mention I have an exterior wall in my attic missing batts...

Rant over. The heat is unbearable in the summer time in my attic and I am quickly understanding why. I'm now wondering if only one ventilation fan will do the job...


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## ionicatoms (Mar 8, 2020)

I'm not a roofing guy, but I would think if you don't have condensation or moisture anywhere in the attic throughout the year then the ventilation and insulation are probably adequate. Verify by checking the opposite side of any surface which is cooled. Ducts and ceilings in the summer. Roof in winter. I once moved into a place where the dryer vented to the attic; check for stupid sh*t like that too.

You could also get some temperature and humidity monitoring if you really want to quantify the performance of your attic relative to outside conditions.

I've read that an attic fan can actually make things worse by drawing in humid air at certain times of day, so I would proceed with some degree of caution even though the replacement is only said to be $600.


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## FlowRider (Apr 7, 2019)

cnet24 said:


> You have no insulation on your roof sheathing, just OSB.
> 
> *For my understanding, what would you use for this application?*


Here is a link for you to show how roof sheathing technology has improved since your house was built:






I had this radiant barrier installed when I built my current home (finished end of April, 2016) in Texas.

The insulation you had blown in will help some in terms of heat getting into the living space through your ceiling sheet rock. But it will not stop the heat from building up inside your attic above it....

My previous home, built in 1997, just had OSB sheathing, no radiant barrier. But I had the builder put in soffits all around the house that were completely ventilated, made of vinyl, and then had the roofer install ridge vents on every ridge, and a thermostat controlled automatic attic fan at the peak.

It helped keep the house air conditioning from being overworked - I had a heat pump for upstairs.

On my new house, I had exhaust vents installed that are not electric - they work via convection and currents created by wind circulating from the soffits up through the ridge vents and exhaust vents. With the radiant barrier OSB sheathing installed, an attic based air handler works so much better.

You can retrofit your existing roof with insulation but I don't want you to stroke out from the cost.... :shock:

If I were you I would definitely install the electric attic fan to exhaust the heated air, and you might want to check on getting more open soffit vents installed to help move air up through the attic itself.


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## FlowRider (Apr 7, 2019)

Here is a real good article to read to help you understand the reasons behind attic air flow designs.

https://www.energystar.gov/campaign/seal_insulate/do_it_yourself_guide/about_attic_ventilation


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## Babaganoosh (Apr 21, 2019)

If you don't have passive ventilation meaning ridge vents, soffit vents (I think I saw those in your pic) or gable vents then you definitely want the fan. There's an issue however if you run the fan and have clogged soffit vents and no gable vents. The replacement air has to come from somewhere. If you don't have adequate venting to pull the air from then it pulls conditioned air from you living space. Yup. An attic fan can pull your nice cool air conditioned air right up and out of your house if you lack air sealing. Did they air seal you attic to floor to your living area ceilings when they added the insulation in your attic?


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## jasonbraswell (Aug 18, 2019)

Agree on the soffit vents.
There is a ratio on soffit vent to attic vent calculation.
I would see how hot your attic is reaching on a hot day and then see about getting better circulation from soffits to the fan.
We had to add several vents on the soffit. The builder did not have nearly enough.
They sold some solar fans at one time and those worked pretty good when I lived in TX.


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## cnet24 (Jul 14, 2017)

I appreciate everyone's input here and love the ability to post on a forum like this (not lawn related) and get guidance!


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## jayhawk (Apr 18, 2017)

They are a disaster. @Babaganoosh sure it's got a hundred holes in the top plate, all vents, lights, fire ext box, worthless exhaust fans...all cut outs that leak.


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## jayhawk (Apr 18, 2017)

Energy Vanguard - great blog

https://www.energyvanguard.com/blog/the-1-reason-power-attic-ventilators-don-t-help/

He didn't do one in his house


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## jayhawk (Apr 18, 2017)

Soffit vents run the length of my house, not just every x feet. Ridge Vent. Still hot AF


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## Thick n Dense (May 7, 2019)

So is it worth it ? I have one thtas installed but mysteraly dont know how to turn on or operate. 
I have venting so its not requies bust missing out oppurtunities it seems


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