# Attic Fan or Not?



## firebroad (Jun 18, 2012)

When I bought my place, I had central air put in the attic of my 1091 sf rancher. At the same time, the installer recommended a thermostatically controlled attic fan installed on the roof. Both of these installations were done at the same time, and I also had a roofer put on a 35 year roof.

Now six years later, the fan is kaput. The A/C guys say this is about as long as these critters last, and will swap it out for about $350.
Doing a little research, I have discovered that
1) Indeed, 5 years is the usual life expectancy of a motor-drivien fan.
2) There are solar powered fans, but I would have to have the p/v panel routed to the sunny side of the roof, and probably should have a thermostat installed--these babies cost more, and some are only warranted for 5 years or so unless you get a Natural Light, which is warranted for 25 years and the nearest installer is on the other side of the state.
3) Have the roofer rip it out, repair the hole and shingle over it, because the roof is equipped with gable vents, soffit vents, and ridge vents. Price at present is not known.

I am neither handy nor strong, (and I don't "know" anyone),so my choices are limited to hiring out.
Any body know anything more than I do that would help me decide which route to go? I do not want to keep forking over $$ every couple of years, especially if a fan is not really doing me any good.


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## fossil (Jun 18, 2012)

firebroad said:


> ...the roof is equipped with gable vents, soffit vents, and ridge vents...


 
Then I don't understand why you have the fan at all.  No real compelling reason to do anything at all about it.  Just make sure it's got no power and forget about it.  Rick


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## firebroad (Jun 18, 2012)

fossil said:


> Then I don't understand why you have the fan at all. No real compelling reason to do anything at all about it. Just make sure it's got no power and forget about it. Rick


Thanks, Rick;  The reason it is there is because a A/C guys thought it needed it.  I knew nothing about the ridge vents, and they may not have been there before I contracted to get the new roof.  I never really liked the idea of that hole up there, letting in bees and such--so you think I should just ignore it rather than get it sealed up?


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## heat seeker (Jun 18, 2012)

The fan will definitely keep the attic cooler, which will prolong the life of your shingles, and reduce the load on the AC. I would replace it. That said, I don't have one, but am considering installing a gable fan to serve the same purpose.


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## fossil (Jun 18, 2012)

The house we owned in Fairfax VA had an existing attic fan & gable end vents when we bought the place.  No ridge vent or vented soffits.  I didn't think much of it...seemed quiet enough.  Turned out it had no power to it ...which I figured out when we were in the midst of a major remodel/addition.  Electrician or someone talked me into a new attic fan through the roof of the new 2nd story addition.  Meantime, the builder incorporated soffit & ridge vents into the new roof and retrofitted them into the existing roof.  I did nothing about the old powerless attic fan, but let the new one operate on its thermostat.  It was in the attic above our bedroom.  I got tired of listening to it run, even after adjusting the on/off temps a couple of times and finally just turned the damn thing off.  The attics vented just fine, and we never had any sort of problem with bug/critter intrusion through the fans.  With generous insulation on the attic floor, coupled with the ridge & soffit vents, I don't know why anything else is needed.  Rick


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## Adios Pantalones (Jun 18, 2012)

Had all our windahs replaced and the dudes left a ladder there for a couple days- so I climbed up to replace the driveway side flood lights- first I banged the ladder around to make sure there was no squirrel home in the vent (we have residents in our log home) and when I got up there- WOW- the heat pouring out the vent was pretty crazy, and it wasn't a particularly hot day. Anyway- I could feel the airflow big time- so the attic was hot, but the air was flowing.


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## fossil (Jun 18, 2012)

Natural convection...shouldn't be a mystery to any of us woodburners. Let the hottest air escape out the top of the attic space (roof ridge vent) while allowing relatively cooler air to come in to replace it from the bottom (soffits). Works like a charm, continous circulation, no forced convection required.  If you don't provide that path for natural convection, then yes, you need something like gable vents and an attic fan.


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## firebroad (Jun 18, 2012)

That is the question--now that you mention, I am not sure about the soffits.  I do see light coming through the edges where the roof meets the walls when I am up in the attic--does that count?  Also, there are two gable vents visible from the outside, but one end seems to be walled up.  Not sure what the story was there.


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## Adios Pantalones (Jun 18, 2012)

firebroad said:


> That is the question--now that you mention, I am not sure about the soffits. I do see light coming through the edges where the roof meets the walls when I am up in the attic--does that count? Also, there are two gable vents visible from the outside, but one end seems to be walled up. Not sure what the story was there.


 
It's probable that a violent mutant was born into the family that had to be sequestered in that attic space at one time. That's like 97% likely.


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## firebroad (Jun 18, 2012)

Adios Pantalones said:


> It's probable that a violent mutant was born into the family that had to be sequestered in that attic space at one time. That's like 97% likely.


Oh, that's were you got to, AP!
I am wondering if it were damage from a chimney fire, or water damage.  No evidence otherwise.


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## Adios Pantalones (Jun 18, 2012)

Ya. Violent mutant. No question.


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## fossil (Jun 18, 2012)

It would make no sense at all to vent the ridge without also venting the soffits. If both ridge vent and soffit vents are present, then the gable end vents are redundant and really don't matter either way. If there are no ridge & soffit vents, then the gable end vents should be clear and the attic fan up and running on its thermostat. Either way, the attic needs to vent...natural or forced.


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## firebroad (Jun 18, 2012)

fossil said:


> It would make no sense at all to vent the ridge without also venting the soffits. If both ridge vent and soffit vents are present, then the gable end vents are redundant and really don't matter either way. If there are no ridge & soffit vents, then the gable end vents shuold be clear and the attic fan up and running on its thermostat. Either way, the attic needs to vent...natural or forced.


Looks like we are back to a fan.


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## Adios Pantalones (Jun 18, 2012)

firebroad said:


> Looks like we are back to a fan.


 
Why? If you have sofit vents, and a ridge vent then you should be fine.


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## fossil (Jun 18, 2012)

firebroad said:


> That is the question--now that you mention, I am not sure about the soffits. I do see light coming through the edges where the roof meets the walls when I am up in the attic--does that count?


 
Can't tell without seeing it.  Soffit vents come in a lot of shapes & sizes, but in every case there's some provision (narrow slits/small holes/screening) to keep out the bugs & critters.  The soffits can be vented by a series of screened openings, a bunch of little round plastic vents, a continuous band of vent through the soffit...any number of ways.  Up in the attic then, care must be taken to not close off the soffit vents when the attic insulation is installed.  Not so much a problem if using batts, but if blown in, then there are special shield deals made to put in place to keep the insulation from piling up on the inside of the soffit vents.  Google "soffit vent" & you'll find a lot of info.


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## BrotherBart (Jun 18, 2012)

I have no ridge vent so I have a powered thermo controlled fan in one end on the gable vent. I am on my second $35 fan. The first one lasted 18 years. This one is on its ninth year. Some noise for sure but mostly in the daytime when I am not upstairs and it made a huge dent in the cooling bill when I installed the thing way back when. I need to get a new roof since this one has been there since 1985 but it is in pretty decent "uncooked" condition. My neighbor didn't put in a gable fan and had to replace his roasted roof after eight years.


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## firebroad (Jun 18, 2012)

There doesn't seem to be any perforations or anything else in the soffits.   I guess I will have to dig out the original paperwork or call the roofer to see what is what.


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## fossil (Jun 18, 2012)

Seeing some daylight looking around the perimeter inside the attic doesn't necessarily mean your soffits are properly vented.  If you're not really sure just exactly what you're dealing with, then there's no question that the best course of action is to get a local professional over there to inspect & assess things with you, and discuss your needs/options.   Generally speaking, proper soffit vents are an easier retro-fit than a ridge vent, although that's doable.  If you have neither a ridge vent nor proper soffit vents, then the gable end vents and a new attic fan win $$$-wise hands down.  In any case, I really think getting a local pro over there is the best thing for you to do.  Rick


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## firebroad (Jun 18, 2012)

fossil said:


> Seeing some daylight looking around the perimeter inside the attic doesn't necessarily mean your soffits are properly vented. If you're not really sure just exactly what you're dealing with, then there's no question that the best course of action is to get a local professional over there to inspect & assess things with you, and discuss your needs/options. Generally speaking, proper soffit vents are an easier retro-fit than a ridge vent, although that's doable. If you have neither a ridge vent nor proper soffit vents, then the gable end vents and a new attic fan win $$$-wise hands down. In any case, I really think getting a local pro over there is the best thing for you to do. Rick


I tend to agree.  I called the roofing company, I hold them in high regard, so when they get back to me I think I will invite them over to take a peek.


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## woodgeek (Jun 18, 2012)

Latest building science says attic fans are not needed. Shingle life doesn't care....what about insulated cathedral roofs? If the attic floor is not airsealed perfectly, the fan sucks conditioned air out of the house, which does cool the attic, but this also drives up your AC costs (!) rather than reducing them. Backed up by some case studies.

Don't see why you need to roof over the hole....if there is no weather coming in, pull the wires and leave the fan in place.


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## BrotherBart (Jun 18, 2012)

woodgeek said:


> Latest building science says attic fans are not needed. Shingle life doesn't care....what about insulated cathedral roofs? If the attic floor is not airsealed perfectly, the fan sucks conditioned air out of the house, which does cool the attic, but this also drives up your AC costs (!) rather than reducing them. Backed up by some case studies.


 
Send'em over here to study. The case study with my neighbor had shingles that looked like ruffled potato chips. My case study dropped the A/C cost by a third in an exactly comparable year.

Cathedral roof shingles live longer because of the extreme slope, less angle of attack from Maw Nature. Any extreme slopped roof lasts longer.


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## woodgeek (Jun 19, 2012)

Lots of defective shingles have been shipped over the years, the neighbors shingles curled up shortly after a fan died?

....and I guess that your attic is airsealed, many are not.


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## firebroad (Jun 19, 2012)

Here's the update on this mess.  I went up to the attic and looked around.  I don't go up there much, it is only 5 ft. high in the middle, dirty, and covered in dead stinkbugs.  Probably lady bugs, too.  Anyway, I noticed that there is only one gable that is ventilated, and there is what looks like at least two cutouts for soffit vents (judging by the  rectangular pinkish glow), but they are covered by the aluminum trim on the outside.  Don't ask me, I didn't do it.  Also, there is a hole a little bigger than the size of a golf ball in the ridge vent where something must have eaten its way in.  The roof guys are coming Friday to sort it out, and let me know what is what with fan business.  
I appreciate all the input I got from everyone, now I'm no less confused, but at least I know the right questions.


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## ironpony (Jun 19, 2012)

I believe in proper venting, also like having my fan.
if you are seeing a difference in utility cost your house is not properly insulated.
if the building envelope is correct, the insulation that keeps heat/cool in also keeps heat/cool out.
you might need more insulation in the attic space.
cathederal ceilings are another issue, they never seem to be able to be insulated properly


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## semipro (Jun 19, 2012)

Firebroad,
You could also consider taking this opportunity to invest in some energy upgrades for the attic.  The payoff period can be pretty short with air sealing and insulating. 
You could seal off the attic and have foam sprayed between the rafters.  This really reduces the summer load on AC and heating load too.


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## firebroad (Jun 19, 2012)

semipro said:


> Firebroad,
> You could also consider taking this opportunity to invest in some energy upgrades for the attic. The payoff period can be pretty short with air sealing and insulating.
> You could seal off the attic and have foam sprayed between the rafters. This really reduces the summer load on AC and heating load too.


The issue is that the A/C unit is in the attic.  There is plenty of insulation on the floor--I put it there myself.  I believe that the A/C installer put in the fan in the belief that it would keep the unit working better.  I am not so sure about the validity of that point, but I will say that I have noticed buckling of the shingles this last year which may or may not have anything to do with the fan's failure.
The roofing company's guarantee is for the next 29 years.  They have so far given me no problems with coming out and rectifying any defects that have come up.  They would stand to gain nothing from the replacement of the fan, as they would not be the ones doing the work.  They may suggest opening the sofits so that the ridge vents work better, but I will know more on Friday.  At the moment, I am more interested in getting that hole fixed before we have a downpour!


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## coaly (Jun 19, 2012)

woodgeek, Cathedral ceilings should have fully vented soffit for intake, and ridge vent to pull heated air up each joist space like chimneys. The insulation is held down with styrofoam troughs to allow the air circulation on the bottom side of roof deck. When this is not done, and there is no air flow present, the roof decking stays damp, gets soft and sags between joists. When you can see the outline of ridges where the joists are, that's the problem.
I had a cathedral ceiling section that has headers across 3 joist spaces for the largest roof window andersen makes. 4 foot wide. Before I closed in the soffit (a few years) the bottom of th eplywood decking was getting black under the eve. It's a 2 foot overhang. I hadn't finished the interior wall board, only insulation with vapor barrier. (It took 14 years to build this place from digging the hole to paint which still isn't done) So i bought a 1/2inch Makita angle drill and bored holes through the joists (2 X 10) just under the roof decking. About 2 inches down, I stapled chicken wire across th ejoist space to keep the insulation down from the roof to allow the joist spaces on the sides of the blocked spaces to pull out the top. It has worked so far.
If I had a problem and needed mechanical ventillation, I was going with one of the roof turbin spinner things that do not require electric. That may be something yo ucan use your roof hole for. The new ones are very quiet with good bearings. A neighbor here put two above his breezeway between house and detached garage. It heated up like a greenhouse in there, and those turbin vents did the trick. They seem to be spinning with or without wind. Possibly just the rising air turns them. He puts a bag over them over the winter to hold some heat in his breezeway since it helps heat the house.
There is also such a thing as balance to the vent system. A full ridge vent doesn't pull equally if the intakes are not balanced on each side. Sometimes soffit used is solid with only vented pieces here and there. It should be ALL ventillated. Certainteed makes a soffit panel fully vented that you can't see the holes like a cheese grater. Here's the stuff;





Here's the roof window that is in the entry way with cathedral ceiling that was getting black under the eve BEFORE I even installed the soffit, so it was WIDE open and didn't get any air flow until I ventillated the joist spaces sideways. It made a huge difference. I then covered the insulation and studs with 1/2" foam board and plank ceder T & G. No sweat of the window or stains that are so common with cold glass and roof windows. 6/12 pitch for good draft in joist spaces, 70 feet long. Thought I'd never get done. Well, it's not.


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## semipro (Jun 19, 2012)

firebroad said:


> The issue is that the A/C unit is in the attic. There is plenty of insulation on the floor--I put it there myself. I believe that the A/C installer put in the fan in the belief that it would keep the unit working better. I am not so sure about the validity of that point, but I will say that I have noticed buckling of the shingles this last year which may or may not have anything to do with the fan's failure.
> The roofing company's guarantee is for the next 29 years. They have so far given me no problems with coming out and rectifying any defects that have come up. They would stand to gain nothing from the replacement of the fan, as they would not be the ones doing the work. They may suggest opening the sofits so that the ridge vents work better, but I will know more on Friday. At the moment, I am more interested in getting that hole fixed before we have a downpour!


 
Having the AC unit in the attice is further reason to bring the attic within your house's insulated envelope. 
If you didn't seal all leaks around pipes, ducts, wiring coming into your attic the chances are that the insulation you installed is doing little but filtering the air moving from living space to attic.

Many shingle manufacturers are backing off of requirements for under sheathing ventilation. 

Depending on climate and location roof ventilation may not even be needed.  "Cold Roofs" are an alternative that is fast catching on.


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## firebroad (Jun 19, 2012)

[quote="semipro, post: 1133197, member: 9487"Many shingle manufacturers are backing off of requirements for under sheathing ventilation.

Depending on climate and location roof ventilation may not even be needed. "Cold Roofs" are an alternative that is fast catching on.[/quote]

Pardon my ignorance, but what does that mean?


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## semipro (Jun 19, 2012)

firebroad said:


> [quote="semipro, post: 1133197, member: 9487"Many shingle manufacturers are backing off of requirements for under sheathing ventilation.
> 
> Depending on climate and location roof ventilation may not even be needed. "Cold Roofs" are an alternative that is fast catching on.


 
Pardon my ignorance, but what does that mean?[/quote]
This is a good reference from the folks at Building Science Corp. It was published in Fine Homebuilding.  It covers both ventilated and non-ventilated (cold) roofs.
http://www.finehomebuilding.com/how-to/articles/a-crash-course-in-roof-venting.aspx


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## mellow (Jun 19, 2012)

I am in the same boat,  I have our upstairs air handler in the attic.  I have soffits and a ridge vent but I also have a window on one end,  during the really hot days I plug in a window fan and let it run blowing air towards the ridge,  my thought is it will help draw air up and out.  I have tried blowing the air out the window but that interferes with the ridge vent.

My main concern is keeping that air handler from roasting.


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## firebroad (Jun 19, 2012)

mellow said:


> I am in the same boat, I have our upstairs air handler in the attic. I have soffits and a ridge vent but I also have a window on one end, during the really hot days I plug in a window fan and let it run blowing air towards the ridge, my thought is it will help draw air up and out. I have tried blowing the air out the window but that interferes with the ridge vent.
> 
> My main concern is keeping that air handler from roasting.


I have a suspicion I will just have to get another 5 year roof fan up there, else spend a sh**load of money. Oh well.


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## woodgeek (Jun 19, 2012)

OK, I get and agree with ventilating the attic for moisture removal (cathedral or otherwise), but think a properly airsealed and insulated conventional attic floor will make an attic fan a moot point re heat load to the house underneath. I also figure the sheathing is R-1.5 under the shingles and less than R-0.3 from the shingles to the atmosphere, so the shingle temp won't care much either about the attic temp. Making the attic 10 degrees cooler might drop the shingle temp 2 degrees.

My air handler is also in the attic, and if the OP is getting a lot of AC load when the attic is hot, she should look over the return ducting...I had 3-4 sq in of gaps in my return plenum, which under 100 Pa suction from the handler let in a bundle of air. Supply side leaks are bad too, but not so bad in a hot attic as pulling that air in.


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## woodgeek (Jun 22, 2012)

firebroad said:


> I have a suspicion I will just have to get another 5 year roof fan up there, else spend a sh**load of money. Oh well.


 
The only moving part is the blower motor, and it is in a conditioned airflow (i.e. cool) when it is running.  Whenever it is hot in the attic, your AC will be cycling...how hot will the motor get during an off cycle...the housing is usually rated to R-5 or better....and it a motor! they are built to run hot.  I have never worried about my handler getting too hot... The controller boards are electronics, and 60-70°C is no bigs.

What am I missing?

I HAVE worried about my condensate pump freezing in the winter, cracking, and leaking in the spring.


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