[SHIBUMI]

Please jump in with your experience with these. The house is 1900 square feet, 2 fans were recommended, not sure what they do for you and if there really work????????

thanks to all

[Blueblaze]

I installed a powered attic fan in a house I built about 20 years ago. It wasn't solar. It just had a thermostat that caused it to run anytime the attic temp was above a certain temp. I suspect that it was much more powerful that a fan powered by a 6" solar cell, though.

It certainly made the attic more pleasant in the summer, but I never noticed any drop in my A/C bill -- probably because the house was so well insulated that the attic temp wasn't much of an issue. Or maybe the reflective barrier I installed on the rafters when I built the house was all it needed. In any case, it quit working after about 5 years and I never replaced it. And that's the main problem I see with these things -- moving parts in a harsh environment. I would imagine that the solar version has an even worse lifespan.

One other thing to consider -- if you have a house fire when that fan is running, your house will burn down much faster. They really need to be connected somehow to the smoke detectors, but I have no idea if you can find one like that today. Mine wasn't, but I had a switch so that I could at least turn it off if there was a fire and I had time to do it.

[villagetinker]

I agree an AC powered fan will move a LOT more air then any solar powered fan, and it will work to continue to lower attic temperature AFTER the sun goes down. I also agree with a suitable way to stop the fan in case of a fire. There have been previous threads on this as well as some very good information on fan with built in fire stop capability.

[Maker]

What issue are you trying to solve?
What factual data do you have to document that there is a problem?
Can any of the attic fan sellers provide you with a written guarantee for performance, temperature reduction, and cost savings?
Would spending the money on better insulation be a better choice?
Would spending the money on more efficient AC hardware be a better choice?
Have you asked your energy supplier to conduct a free energy audit? See if they have a thermal imaging camera to look for insulation and window problems.
Are the existing soffit vent openings clear or blocked with insulation? Are there more than enough vents? Are baffles in place?
Why did they say "two fans"? Why not one, or three, or four? How did they come up with that?

You can put a remote temperature sensor in your attic and see what the actual temperature is. Maybe your attic is not as hot as you think.

Outside air moves via convection from your eaves to exit the vents at the top of the roof. Adding a powered fan often changes that. Air gets drawn into the existing vents by the fan. Natural convection is reduced, and the entire attic remains about the same temperature. This will always happen when the fan is placed anywhere near existing vents. The airflow becomes into the peak vents, and then out the fan. There is no airflow into the attic from the soffits. The attic air space below that fan height is stagnant, and hotter. Exactly opposite from expected.

The only fan I have ever witnessed being somewhat minimally effective was in a 2 story house, on the ceiling at the top of the stairs. They would open windows and turn it on after the outside temperature dropped below the inside temperature. That cooled off the living space and brought in fresh air. Effective only at certain times of the year; when weather conditions were right (low humidity); and when timing worked out (not hours after coming home to a hot house).
He was a geek and wondered if he could cool the attic space. Collected loads of temperature readings. When running it all day to see if it cooled the attic on a sunny day, or lowered the interior temperatures, those numbers showed no detectable change between running or not, comparing similar days. That was a different use case though... pressurization of the attic space, vs putting it into a net vacuum.
That unit had insulated metal fireproof baffles that closed when it was off. It also was not quiet. Because of the limited usage, he said he would not have put it in if he were able to go back in time.

[Malsua]

Originally Posted by Rich Iwaszko

Please jump in with your experience with these. The house is 1900 square feet, 2 fans were recommended, not sure what they do for you and if there really work????????

thanks to all

Yes, they do work.

No, I don't sell them. I am a licensed home inspector and I also do thermographic inspections for heat/AC loss and water damage.

From personal experience my Courtyard Villa was a blast furnace if you pulled down the stairs after noon on any sunny day. Now that I've installed two Solar fans? It's hot, but not Satan's breath when you open it.




What I see when I do inspections is about like this. If the ridge vent is performing properly or there are passive vents and the attic is reasonably ventilated, a Solar fan probably won't do that much. In fact, mixing venting can be a bad thing because a solar fan can scavenge from the ridge vent and recycle the hot air, not moving much.

If your ridge vent is a super small and the attic is super hot, a solar fan will help. There is also the issue with left over sheathing during builds that prevent the proper movement of air in the attic space. Some builds have a bunch of sheathing inside that needs removed to help with air flow.

Below you will see two ridge vents. One is working properly, the other is missing entirely. That second one needs a solar fan, opening or something.

[JohnN]

I had Solar Guys install an electric vent fan in the garage, pulling the air into the roof.
My garage is reasonably cool, outside temperature but shady. The attic is a bit warmer, but not stifling hot.
Do I have quantifiable cost savings on my A/C? No I don't, but the garage temp is pleasant enough and with the attic quite cooler, I have to think there is some savings.

The electric fan can run 24/7 and it was quite affordable. I'm happy with it.

[Battlebasset]

Originally Posted by Malsua

What I see when I do inspections is about like this. If the ridge vent is performing properly or there are passive vents and the attic is reasonably ventilated, a Solar fan probably won't do that much. In fact, mixing venting can be a bad thing because a solar fan can scavenge from the ridge vent and recycle the hot air, not moving much.

Excellent post. We have the ridge vents and were told pretty much the same thing. If you start adding fans, other vents, it will impact the ridge vent process and efficiency.

I have seen fans that pull more in from the soffits so as to aid the ridge vent. But when you factor in the cost vs savings, assuming your attic has good insulation, I can't imagine it would be worth it.

Bottom line, Florida is hot much of the year. Turn up your air and live with it.

[retiredguy123]

Originally Posted by Battlebasset

Excellent post. We have the ridge vents and were told pretty much the same thing. If you start adding fans, other vents, it will impact the ridge vent process and efficiency.

I have seen fans that pull more in from the soffits so as to aid the ridge vent. But when you factor in the cost vs savings, assuming your attic has good insulation, I can't imagine it would be worth it.

Bottom line, Florida is hot much of the year. Turn up your air and live with it.

I agree. Who cares how hot the attic is? Show me the data where you are actually saving money on electricity.

[Malsua]

Originally Posted by retiredguy123

I agree. Who cares how hot the attic is? Show me the data where you are actually saving money on electricity.

The issue we had was that the AC could not keep up. Interior temps would creep up to 78 or 79 and the AC ran almost 24/7. Our normal set point is 76.

Now? The house and the garage stay cooler, the AC doesn't struggle. The garage went from intolerable to just warm.

Saving money? I don't know, it would seem so. We definitely improved comfort.

I'll say again, unless you've got a problem, Solar fans aren't going to help you. My ridge vent is cut to code minimum and the roof is new, getting it fixed at this time isn't worth it, so the fans made sense and work for me. Your mileage may vary.

[Battlebasset]

Originally Posted by retiredguy123

I agree. Who cares how hot the attic is? Show me the data where you are actually saving money on electricity.

As I think about this, gluing some foam board to the backside of my indoor attic access might be worth the money/effort. It would be a non-insulated point as there would be no blown in insulation on the top of it.

When I lived up north, and being cheap, I built/put a box fan into a piece of plywood that then was placed into my upstairs indoor attic access opening. The fan pulled from the house and into the attic and with the windows open on a cool night, it actually made the house cooler. Sort of a poor man's attic fan.

I might give that a try in my garage down here. Cheaper than installing a fan in my roof, and no need to cut into my roof. If it doesn't help, I'm out my time, and being retired, I have some of that to spare.

[SHIBUMI]

thanks for all the info........looks like a no go for reasons mentioned

Originally Posted by Battlebasset

As I think about this, gluing some foam board to the backside of my indoor attic access might be worth the money/effort. It would be a non-insulated point as there would be no blown in insulation on the top of it.

When I lived up north, and being cheap, I built/put a box fan into a piece of plywood that then was placed into my upstairs indoor attic access opening. The fan pulled from the house and into the attic and with the windows open on a cool night, it actually made the house cooler. Sort of a poor man's attic fan.

I might give that a try in my garage down here. Cheaper than installing a fan in my roof, and no need to cut into my roof. If it doesn't help, I'm out my time, and being retired, I have some of that to spare.

[Mrmean58]

Originally Posted by Rich Iwaszko

Please jump in with your experience with these. The house is 1900 square feet, 2 fans were recommended, not sure what they do for you and if there really work????????

thanks to all

I had two installed and would do it again. I also had insulation placed over my lanai and garage along with a radiant barrier. The attic stays much cooler protecting the items we have stored over the garage.

[Resident]

Originally Posted by Rich Iwaszko

Please jump in with your experience with these. The house is 1900 square feet, 2 fans were recommended, not sure what they do for you and if there really work????????

thanks to all

Ask the installer for written specs on the solar attic fan -( ie -what is the cubic feet per minute the fans will move). If you’ve got a 1900 sq foot house - the attics volume (cubic feet nor sq feet) is going to be much more and all solar fans are vastly “undersized”. These are not the large ac powered “attic fans” of the past that move vast amounts of air- solar fans resemble small little hand held fans that you might get at an amusement park to cool yourself off (just stuck into a tube vent on your roof) Not going to do much for a massive cubic foot attic space. I speak from experience working in attics throughout the villages. No noticeable difference at all between homes with or without the solar powered fans. What makes the most difference is lighter colored shingles on the home.

[Rwirish]

Save your money.

[Bridget Staunton]

My hubby said (40 years in HVAC) said they are useless use fans powered by AC