Attic fans: cost efficient

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bcc87's picture
Status: Bronze Member (Offline)
Joined: Jul 14 2010
Posts: 52
Attic fans: cost efficient

Following up previous thread of cost effective energy items, I have 2 gable attic fans that were recommended by my HVAC friend to put in my home.

I was doing some reading, and some say while you will save $$, you won't get the return that is advertiesed (which I believe as well). But it will

make my AC unit run less which in return will save $$ during peak pge hours.


Any thoughts, experiences?

LogansRun's picture
Status: Diamond Member (Offline)
Joined: Mar 18 2009
Posts: 1444
Re: Attic fans: cost efficient

They've worked well for me thus far.  I have 2/30 amp, solar fans with hanging thermostats that kick on when the temp in attic hits 80 degrees, and turns off when it gets back down to 70 (which means that in the summer, they never turn off).  It's been extremely hot this year so I can't really give you an "it's saved me $" quote, but I have noticed that my A/C is able to keep up with the heat, whereas in years before it would always be a couple degrees hotter than what I wanted it.  

One thing, if you get fans make sure they have a battery pack.  Mine don't and if you get any cloud cover they'll shut down without backup power.  I was unaware of this when I bought them (I assumed they had it).  I know Costco has fans that are ready to go for about $200 or so (could be wrong on price).  

deggleton's picture
Status: Gold Member (Offline)
Joined: Mar 18 2008
Posts: 250
Re: Attic fans: cost efficient

I wonder where in the world you are.  In most cases/places, replacing highly heated attic air with outdoor air is your goal.  In general, installation of such fans should follow steps (air sealing & insulating) to put your attic outside the thermal boundary, which defines the conditioned space of your building.  Make sure no air from your living space can find its way to the attic, because if it can condensed vapor will cause problems in/after the colder part of years.

"Compared to poorly ventilated roofs, good roof ventilation helps to keep attic temperatures lower.  But expect less savings from improving attic ventilation compared to radiant barriers and sun-blocking measures, because attic heat gain is dominated by heat radiation."    Residential Energy (2009) by J. Krigger & C. Dorsi

(the community has been on this topic at least once before)

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