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Old 05-01-15, 03:28 AM   #1
gtojohn
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Default Solar attic fan built

Trying to stay ahead of summer this year. I have a dead area in my attic which would be conducive to heat gain. Its also right where a hvac system is. After pricing out solar fans and trying to snipe a few on ebay I built one myself. I bought a 30 watt pv panel on craigslist for $40, new 10" 12volt dc car radiator fan for $16 shipped, and a gravity roof vent for $20. The fan's tag says 80 watts. My 30 watt panel can make it scream. It seems the gravity vent restricts the flow somewhat. I could feel the air chop near the fan blades. I added a fan shroud made from a 12" duct start collar and it helped the fan draw more suction. Super easy way to use free power!

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Old 05-01-15, 07:43 AM   #2
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Very cool.

My father in law said the local restore had some PV attic fans for sale for $100. I have yet to check it out though.
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Old 05-31-15, 12:53 PM   #3
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I checked my attic temperature probes yesterday. Its been about 3 weeks since I last checked. I keep one on my attic floor an inch above the insulation. Max reading showed 99f. My other probe is near the new attic fan, sitting on top of my furnace return plenum about 2' from the roof deck. Max reading showed 113f! Thinking about how much warmer this space must have been without any nearby ventilation. This month the weather has been unusually very cloudy and rainy. Summer will be the true test.
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Old 06-01-15, 07:31 AM   #4
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How loud is it when its running?

My father in law just picked up a solar attic fan from the local restore for $100. Its very quiet.
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Old 06-02-15, 08:30 AM   #5
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When its up to full speed I can hear it in the driveway. It makes a whirl noise at high rpm. I cant hear it inside, even in the bedroom adjacent to it. What I've seen for various fan models is the panel size varies quite a bit. The one at the home improvement stores don't spec wattage. Additionally the fan blades can be a bit smaller. Right after I did this I found a solar roof vent thrown to the curb. looks like a bad motor, but the panel is much smaller. I might build another for my upstairs attic if I find another cheap panel.
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Old 06-05-15, 02:03 PM   #6
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Wow, congrats on building it yourself! That's the kind of ingenuity I like to see. So far it sounds like it'll be quite promising for keeping the heat under control. Depending on your climate, this could pay big dividends in keeping your home in good repair over the years.
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Old 10-10-15, 11:18 AM   #7
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I checked the max recorded temp logged on the thermometer near the attic fan, Summer high attic temp was 131F, with our hottest daytime exterior temp at 105F. Attic floor above the insulation max temp was 117F according to my notes, that one I check and reset regularly.
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Old 11-16-15, 12:20 PM   #8
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Was it noticeable after the installation, either in comfort or A/C reduced use?

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