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Combining an attic fan with a ridge vent

18K views 29 replies 13 participants last post by  GoodStuff 
#1 ·
I would like to add an attic fan onto a roof that already has a ridge vent. I know that the two will not work together well if you put the fan 2ft from the peak like you normally do.

Where is the best place on the roof to install this attic fan so it will do the job it's designed to do?
 
#4 ·
Customer has an attic area they would like to use for storage that is incredibly hot.
Useless and unnecessary if you have proper soffit to vent ratio
As an electrician, I often work in attics during the summer months. "Proper" venting may be enough, but it sure doesn't make it comfortable or habitable up there.

Getting this attic space cooler is my main concern. If somebody knows where the attic fan should be placed in relation with the ridge vents, I'd be very appreciative.
 
#5 ·
If its a gabled roof,I'd put a louvered fan in as close to
the peak as possible.
Since this is only for getting the attic cooler,which will extend
the life of the shingles and cut back on air conditioning,it won't need
to run during winter months when moisture laden heat migrates
into the attic and needs to be extracted.
Having a louvered fan will keep it as a separate system,not
interfering with the natural venting needed during the winter months.
 
#6 ·
Since this is only for getting the attic cooler,which will extend
the life of the shingles and cut back on air conditioning...
Personally I can not agree with either of these ideas unless very specific conditions are met and those conditions are almost never met in the average house.
If the interior of the house is not well and completely air sealed then the fans will tend to draw conditioned air from the interior of the house to the attic. That will tend to cool the attic alright at the extra expense of air conditioning.
I don't have any specific conditions for the roof shingle only to say that I am not of the mind that there will be an appreciable difference in the life of the shingles with or without a fan to cool the roof deck.

Andy.
 
#11 ·
My thinking on things like this is if there's that much, that hot of air up there, there's not enough of that leaving. The (gable) vents in our house just pump out the hot air during the summer. It's quite impressive actually.
 
#13 ·
My house, when I bought it, had vented soffits and gable end vents.

I installed a fan in one of the gables and it cooled the house much better. A couple of years down the road I had a new roof installed with ridge vents, and continued to use the gable fan. It cooled as well or better than before.

A few years ago I pulled out all the insulation and had the roof sprayed with foam, closed up the gable vents and have saved a ton on heating and cooling costs.

My advice to the OP is throw the fan in and see how it works for you, they are not that expensive....
 
#14 ·
My advice to the OP is throw the fan in and see how it works for you, they are not that expensive....
Push comes to shove, that's what usually happens. But the fan is only part of the cost if you're not following best practices all the way. That's why there's so much debate every time a situation like this comes up.

I would and do take liberties with stuff like this in my own house, but for customers I pretty much play it by the book.
 
#21 ·
You can make things a little more simple and make the area somewhat air tight, and just blow a much smaller CFM of air into it. Think using radiant barrier that isn't a vapor barrier (or poke holes in it with an ice pick) to define the storage space, and vent to the attic above the highest storage point. Fewer possible issues.
 
#24 ·
I think you have to make the fan big enough so it has to draw air through the soffit vents as well as the ridge vents to be effective. Put it wherever it's convenient. If you finally figure out that we're trying to tell you not to have a fan and ridge vents, then put it up high after you close off the ridge vents.

I didn't think sparkies were so dense.
 
#27 ·
So, the answer has a lot to do with having proper ventilation to begin with...

I've ran into this situation many times - everyone loves to store things in their attic and too many attics are sweat boxes. In almost every case, I have found the soffit vents are either plugged and not breathing, or there is simply not enough soffit vent for the area to breathe properly. There should be 1-1/4 times as much "free space" venting through the soffits as there is vent space in the roof vents. Think of it in terms of intake and exhaust. There are Styrofoam inserts available that fit in-between the rafters and allow the soffit vents to breathe without the fear of insulation covering the duct space... I have also cut custom vent "breathers" out of 6" ducting that sat on the top of the soffit coverings to free up space for the soffits to breathe. In some cases more vent openings need to be cut into the soffits to achieve the 5/4 ratio of vent space.

Accounting for the opening size of the ridge vent AND the power vent is just simple math... compare that to the opening sizes of the soffit vents and you will have your answer - you can't draw more air than is available though, so justifying the answer without taking the soffit vent area into account is a mistake.
 
#29 ·
It is improper to have 2 types of vents in the attic space. Ridgevent works good although it does nothing for humidity. Exhaust fan works good, but the motors tend to last about 10 years and 1 month. (just past warranty) Also, nobody realizes when the motor stops working. It may be years before someone notices.

Whenever you put in an attic fan, it will draw air from the point of least resistance. In your case, without seeing it, it will pull air from the ridge vent. I have seen people install attic fans near pot vents. (I don't know the current term, but they are the ones where you cut small round holes in the roof and put a cover over them) When the attic fan kicks on, it pulls air through the pot vent. If it's raining, it pulls the water through also.

It was mentioned to seal the ridge vent. If you are going to do an attic fan. I think you need to close off the ridge vent. Great stuff will work. You could also remove it completely and install new ridge cap.

I realize not all attic fans go bad after 10 years and 1 month. I have seen alot though.
 
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