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Went to Lowes to look at attic fans...

A

arcas

Platinum Member
I've been thinking about installing a temperature/humidity-controlled fan in the attic. They come in 3 forms: the powered dome thingies that you install in place of the passive aluminum roof vents, gable fans and whole-house attic fans. The powered dome thingies operate at around 1000-1200cfm, the gable fans are around 1500cfm and the whole-house fans really vary...5000+ cfm.

Anyway, what struck me was the amount of power these fans draw. The powered dome thingies operate at around 8-9 cfm per Watt. The gable fans were around 5 cfm/Watt. The whole-house fans were around 14 cfm/Watt.

For comparison, one of my computers has a 109cfm 4.75" fan that draws just under 7 Watts. That is, it's delivering 15.57 cfm/Watt! It used to have an all-metal 130cfm 4.75" EBM/Papst fan that drew around 7.5 Watts --> 17.33 cfm/Watt. I replaced it because of noise 🙂

Now, I realize the intended uses of an attic or gable fan is completely different from those of a 5" muffin fan. But it's very interesting that a 5" muffin fan is over than 3 *times* more efficient than the gable fans people are installing in their homes. It's also interesting that only the whole-house fans approach the efficiency of muffin fans.




 
We went out and bought a solar powered attic fan. It was much more expensive than a typical electric one, but it easily made up for the price difference when you consider the cost of running it for a year and the cost of an electrician to run a circuit to it. It took me about 1/2 hour to install - Hardest part was going into the attic and marking the spot centered between the rafters!

Think about the solar powered ones, if you're looking. You won't be sorry.

- G
 
Strange you should mention the comparison, I was looking around my attic this spring & using the same mindset that I use for cooling my pc case.

I'm thinking of doing some custom ductwork & modding a solar fan to vent under the eaves rather than cut another hole in my roof...
 
Haven't seen any solar-powered versions. How much do they cost and what's the CFM rating?

Pliablemoose: haha. I thought I was the only one looking to apply experience gained from case cooling to my attic situation 🙂

 
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