Solar-powered technology for This Old House
Able to tear myself away from The Discovery Channel for just a moment, I caught an episode of Ask This Old House, which featured some new house gadgets that I found very clever: solar-power attic fans. Manufactured by Solatube, Air Vent, Sun Rise Solar and others, these devices use integral photovoltaic cells to power a roof- or gable-mounted fan. The fan runs anytime the sun shines, year-round, to ventilate the attic space of a house. In summer, the fan reduces overheating in the attic; in winter it keeps the attic cold, which helps to prevent ice dams on the roof. The year-round ventilation also helps to keep the attic air spaces dry and free from moisture damage.
Posted: Sunday, Apr 1, 2007 5:51 pm by adam
File as: Energy; Wind, Solar and Hydro
Comments
Comment from Cape Cod
Time: Monday, Apr 2, 2007, 9:43 am
I came across these a couple months ago while looking for a way to vent my attic space. The DIY (no electrical wiring) is also a very appealing aspect. You can also get a temperature sensor, so the fan will only run if the attic temperature is say 80+ degrees. I am considering the one with the detached solar panel so it can be placed where the sun shines (on the roof), while venting the attic through the gable end.
These would also be a great way to “cool” a small outbuilding.
Comment from adam
Time: Monday, Apr 2, 2007, 11:16 am
Thanks for your comment. A thermostatic control does seem like a good idea. And for a small structure, this type of fan would probably work quite well as a whole-house fan for cooling. Please let me know how it works out for your home.
Comment from Dave Brooks
Time: Tuesday, Apr 3, 2007, 2:23 pm
It would have to be a *really* small boulding for whole-house cooling. They seem to be about one-foot fans, and with 12-volt DC batteries they can’t be too zippy. It takes a lot of ooomph to move air: My attic fan is about three feet in diameter and on household current so it can wail as needed, but even so it doesn’t get to the entire house. Plus, of course, these won’t work at night or on cloudy days. Good idea for attics, though - but I agree you’d need a detachable solar panel to get maximum solar power.
Comment from adam
Time: Tuesday, Apr 3, 2007, 6:02 pm
Yes, you are right; the size would be quite small. Of these fans, the largest I could find claims to move about 1250 cfm. I estimate that at this would sufficient for only about 300 square feet of living space. Attic ventilation would be the best application, rather than house-cooling.
These fans don’t use batteries as far as I can tell. They seem to direct drive a dc motor. From what I saw on the show, they will work on cloudy days, provided there is some ambient light. But the amount of air the fan can move will depend upon the amount of available light.
Good comments, thanks!
Comment from Bill Chicago
Time: Tuesday, Apr 10, 2007, 12:18 am
Great show and fascinating gadgetry!
I am about to re-roof my cedar shake roof and have been told by a very knowledgeable and straight-shooting roofer that I should not reinstall the two large, thermostat controlled attic fans (they are pretty old!), but instead should just add a few more vents (passive box vents).
He swears by them and uses a formula to determine how many one should have to support an attic of a certain size…in my case (c. 2,000 square feet) a minimum of 11 units…with more being fine too. These are low cost units.
The current roof includes two fans and about 6 of thes box vents, but the roofer tells me (with a smile on his face) that the moisture is exiting one opening only to be drawn back into the roof by another and that the fans are useless and only complicating what should be very simple venting process.
Though we live in Chicago, the southern elevation of the house is in open sun and during the summer months the attic can easily exceed 100 degrees.
After seeing the recent broadcast featuring the solar fans, I was considering a combo-solution, i.e., replacing the old fans with these newer models as well as installing new, low-profile box-vents…and more of them.
What’s the truth about this science? And what approach do you recommend?
Many Thanks,
Bill
Comment from adam
Time: Tuesday, Apr 10, 2007, 6:44 am
Bill, you’ve presented some good questions. Although a homeowner, I’m not really qualified to answer your question, and would have to assume your roofing contractor knows what he’s talking about.
None the less, my opinon is that active ventilation is better than passive. I don’t buy his argument that a fan is somehow not an improvement. And I would think that you’d want all the ventilation you could get, to avoid moisture damage to your cedar shakes. If nothing else, reducing your attic temperature will also be beneficial toward keeping your house cool in summer.
I suggest you post your question on some reputable home/garden sites. In particular, I’d recommend Fine Hombuilding magazine, which runs a very good site with a forum for questions, although you’ll have to join as a member to get access to the forums (http://www.finehomebuilding.com).
Best of luck, and do let me know how things turn out.
Comment from MC Solar Power Marr
Time: Friday, Mar 14, 2008, 10:05 am
This is an interesting post on solar power. I bookmarked it so I can return and follow the progress. I have a solar power Website at http://www.online-solar-products.com/ and a solar power Blog at http://www.online-solar-products.net/ that I think you will find interesting.
Comment from Monica
Time: Tuesday, Apr 22, 2008, 11:49 am
Hi MC Solar POwer Marr!
I did not find any information on the Solar POwered Attic fans on your website. Would you care to reccomend one for a 2500 sq.ft. home.
Thank yoU!
Regards,
Monica
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