Solar Attic Fans

[Shockah]

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Cheap Attic, Bilge, or Compartment Fan.

30watt Bilge Blower/50watt Panel... nothing in between.
Volts as high as 16.5
Blower begins blowing at >3v.

[russ]

OK, somebody got careless with the Moderator editing tool and inserted someone else's words in the above post under my name. Whatever happened, the above reply to Naptown did not come from me.

I doubt Mike did it and I didn't so careful with the finger pointing - these forum platforms are generic I suppose - easy for someone to play games.

[inetdog]

The use I have in mind is actually for a garage which has only small passive louvered gable vents. In the summer it gets really hot and makes the workshop area almost unusable.
I can put money into radiant barrier insulation on the inside of the uninsulated open truss roof, or powered gable fans, or something solar. Any thoughts on the respective merits of each? (Almost forgot: Currently there are no floor level or other vents in the walls, but I do have screened windows on the shaded side that can be opened if I remember.)

(I have seen discussions of line-powered fans that say the Home Depot type will only last a few years, but touting a $400 line-powered German model. Are there lifetime issues with the solar-powered DC motors?)

The summer outside temperature does not get much above 100 on the worst days, but the inside of the garage can easily get 20 degrees or more hotter at head level and intolerable up near the roof.

OK, somebody got careless with the Moderator editing tool and inserted someone else's words in the above post under my name. Whatever happened, the above reply to Naptown did not come from me.

[stev]

I want to put a box fan in the gable end of my house.
I have a 105 watt solar panel to run it.
A new Grape Solar fab 8 from Home Depot.
Any 12 volt box fans? Any ideas?
Good idea on the radiator fan from the auto junk yard.

[Wy_White_Wolf]

I took an old cooling fan and it's relay out of a junker car. Wired the relay to a snap switch to acitvate and a 100W solar panel. Turns on about 85F and off at 75F. Works great and was alot cheaper than the premade units. I only expected it to last a year but it's starting it's 3rd year and running strong.

WWW

[Volusiano]

I have 3 solar fans from Home Depot, mounted and sealed to the roof under 3 of the 5 "metro" metal roof vents. I have a continuous soffit with ducts between trusses.
I attached 60 watt panels to each of them. They spin fast.
My attic has radiant barrier on top of the fiberglass insulation and my attic temperature has lowered substantially.
135 degrees was common in the summer, now it doesn't exceed 105.
They have been in operation for over 14 months, I feel they will pay for themselves over time.

I'm in South Florida, Your mileage may vary

How are you able to attribute how much of the lowered attic temperature to the radiant barrier and how much due to the solar fans? I would guess that much of it is due to the radiant barrier.

[inetdog]

They are not for everyone! Most likely no roof penetrations in hurricane country are acceptable.
They work great here in NY.

Interesting.
I have no doubt that they work great in the sense that they can be seen spinning.
But there have also been some credible studies that purport to show that in terms of actual air movement, a pivoted fixed vent (keeping the horizontal opening downwind) without the obstruction inherent in the whirlybird actually does a much better job at less cost and with smaller roof openings.
If there is little wind, then the restriction to air movement that the whirlybird provides makes the ventilation much worse than an open vent (with a rain cap).

[russ]

Seems to me like a radiant barrier and a air mover fan is your best bet.

[inetdog]

How about vents for a detached garage?

how much they help is dependent on how the attic is ventilated now. But generally they are not worth much.

The use I have in mind is actually for a garage which has only small passive louvered gable vents. In the summer it gets really hot and makes the workshop area almost unusable.
I can put money into radiant barrier insulation on the inside of the uninsulated open truss roof, or powered gable fans, or something solar. Any thoughts on the respective merits of each? (Almost forgot: Currently there are no floor level or other vents in the walls, but I do have screened windows on the shaded side that can be opened if I remember.)

(I have seen discussions of line-powered fans that say the Home Depot type will only last a few years, but touting a $400 line-powered German model. Are there lifetime issues with the solar-powered DC motors?)

The summer outside temperature does not get much above 100 on the worst days, but the inside of the garage can easily get 20 degrees or more hotter at head level and intolerable up near the roof.

[tonystewart]

They are not for everyone! Most likely no roof penetrations in hurricane country are acceptable.
They work great here in NY.

Did your area receive extensive wind or water damage from the last hurricane?

[LucMan]

Do you know what we call those in South Florida? Hurricane openings! The new roofing codes won't even allow them to be installed. No roofer will touch those in South Florida.

They are not for everyone! Most likely no roof penetrations in hurricane country are acceptable.
They work great here in NY.

[tonystewart]

Take a look at the Whirlybird attic ventilators, just a slight breeze and they spin removing humidity and hot air from the attic.
http://www.ehelpfultips.com/do_whirl...vents_work.htm

Do you know what we call those in South Florida? Hurricane openings! The new roofing codes won't even allow them to be installed. No roofer will touch those in South Florida.

[LucMan]

Take a look at the Whirlybird attic ventilators, just a slight breeze and they spin removing humidity and hot air from the attic.

http://www.ehelpfultips.com/do_whirlybird_vents_work.htm

[tonystewart]

If I have a single 120w solar panel, can I safely power two of these fans?

Yes, no, maybe, depends on voltage, amperage, etc. Kinda vague

[peakbagger]

Hey Tony, up in NH if the conditions are right, I get snow blowing in the upwind gable end vents even though they are louvered. I have a big plastic tray that hangs below it to catch the snow so it can melt and evaporate before it gets into the insulation. With snow, the ridge vents can get covered with snow and stop air circulation up through the soffit vents causing ice daming, thus the gable end vents. I guess regional conditions always factor in.