Your Questions About Solar Powered Attic Fan

Mark asks…

Can you get wind powered window fans?

OK, my parent's attic has two small windows. The windows don't face the ocean, which is unfortunate, because there is a sea breeze. I'm wondering if there are:
1.) wind powered window fans, OR
2.) solar powered window fans.

I'm also wondering if it would be dangerous to stick a window fan in the windows, if they can't go up to the attic to maintain it. Would it be in danger of over-heating?

ssadmin answers:

Or 3.) put a window on the other side of the attic.

Richard asks…

90 degrees and no power. Need solar fans or something else.?

Where can i find solar indoor fans? I am not referring to Attic fans. My family lives in Africa where they have power shortages that last for 2 weeks or more.So i want to get them a couple of solar fans. Something bigger than the portable fans. If you have alternative ideas please give me your suggestions?
A solar fan is a fan powered by sunlight. I found some portable ones, but i wondering if i can find something a bit bigger.

ssadmin answers:

There is a project that several groups at GVSU have been trying to perfect for a couple of semesters now involving a fan that operates on hanging weights. It is difficult to describe in words, but basically a gear reduction slows down the speed of the dropping weight so that it lasts for at least a half hour or more on every “charge”. The system they're working on is being designed for similar applications in Central America, and the prototype has been built using mostly discarded parts: used rebar, old fabric, bike sprockets etc.

Mary asks…

What size of solar panel would I need to power a small extractor fan?

I am in the process of building a passive heating system for my house. My house has a largish crawl space under a dark grey tin roof, which heats up enormously.
I am thinking about buying small extractor fans and install them so that they channel the hot air from the attic down into the rooms through pipes which exit into the rooms via ceiling ports.
I want to power the fans by solar panels, so that sunshine automatically makes them blow the hot attic air down into the house.
I live in southern NZ, with temperatures, sunshine hours, and intensity comparable to those of Northern California.
What size of solar panel do you reckon I would need to ensure proper functionality?
Thanks for your advice.
I am perfectly open on performance specs of the fan heaters, if necessary, I'll even build my own. All they need to do is shovel down air. Every little helps.

ssadmin answers:

I have seen some 24 Volt DC, 18 Watt fans used to ventilate a portable restroom, and they seem to move a fair amount of air. You might do well with 40 Watts of solar and a couple of fans that size.

Sharon asks…

why don't houses use eletric fans to cool attics poosible solar power?

ssadmin answers:

Lots of houses use aftermarket solar and conventional electric attic fans, and these products are widely available. These require prep work to make them really effective at keeping the attic cool. Plenty of soffit and/or gable vents are required to draw cooler air in while the attic fans are pulling hot air out the top. If the attic isn't ventilated well enough, the fans will be all but useless.

Solar attic fans have polysilicon photovoltaic cells that generate plenty of power to move several hundred CFM if your attic is well ventilated and if you have ample sunlight, preferably on a roof that slopes to the south or southwest. I have two of them rated at 1000CFM and they work great — i save $75-$125 a month in electricity for air conditioning during the summer. Conventional electric (120VAC) attic fans are much cheaper if you are handy enough to wire them yourself. Hiring a separate electrician to do the wiring can be $$. The cost of the electricity used by an attic fan is minimal.

Most newer houses don't have attic fans unless you custom build, but they do have R40 or greater insulation to keep the house cool and plenty of soffit / ridge / gable vents to keep the attic ventilated. A homeowner can easily add (a) solar attic fan(s) on top of the roof if needed.

Jenny asks…

If I add 4 large 12V computer fans to my roof vent and power them by a solar panel, will it make a difference?

i would like to construct 4x 12VDC computer fans under my roof vent. These would be wired in parallel to a 12V solar panel (Wattage depending on size of fans). I know this would only work during the day, but that's really all I need. My question is, would this make a difference in the temp in the attic or am I wasting my time. Really, I don't want to spend $300 of a pre-made kit and have to replace the vent.

ssadmin answers:

We had a solar vent put in our roof, and were amazed at how much cooler the house got. Years later, the house was still cool, but when I went up to check the fan, I found that the solar panel had burned out, and the fan was not moving. Apparently, just having a large vent near the ridgeline, even without forced air, is enough to make a huge difference.

If I had to do it again, I would put one of those wind-powered vents, the kind that looks like a turban, up there. In our neighborhood, those things have been on people's rooftops for like 20 years. They've rusted, but I still see them turning in the breeze.

If you really want to use the existing vent, maybe consider one of those really powerful attic fans, that plugs into AC. You would only need to run it on low, or maybe just for a few minutes to clear out the hot air.

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