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  #41  
Old 07-04-2012, 08:45 PM
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As a licensed Florida Home Inspector, and one who has inspected more then a few homes in The Villages, I will tell you that everything I have read and studied state that Solar powered vents are a bad idea. I know there are companies out there that will tell you different, but one must ask if their info is designed more to make a sale, or is it based on current industry studies.

A typical Attic is designed to pull cooler air passively from the soffits up through either a ridge vent or non-powered roof vents placed close to the ridge. This natural convection works well as long as you have the proper amount of ventilation.

When you install a powered vent, it will take air from the least resistance. This usually is from the already installed ridge vent....thus "short circuiting" the natural convection from the soffits and leaving much of the attic with less air movement.

Worse, sometimes they can produce negative pressure from openings in the living space ceiling and draw CONDITIONED air from the interior of the house into the attic....costing you money. Now this would not happen if you had a completely sealed ceiling, but I have YET to see one. If your ceiling was totally sealed and well insulated, you would then not care about attic temps.

This negative pressure could also cause backdrafting from a water heater and put carbon monoxide into the house.

Studies have shown that powered ventilation may lower the temps up by the ridge by about 10 degrees, but the temps right above the insulation show a drop of less then 5 degrees.

David Butler, author of Optimal Building Systems states that putting the pressure imbalance issue aside, there is simply not a good payback. Let's say one spends around $400/year on A/C. (I know that is low for around here, but bear with me). Ceiling loads typically represent 10 to 25 percent of your cooling costs....which would then be between $25-$100 dollars. It's a well known fact that radiant gain from the roof makes up well over half of the ceiling load, (that is why many folks feel radiant barriers are a good idea in our climate). If you assume a 50% figure, and the difference between your interior temp (let's say 77 degrees) and your lower attic temp drops from let's say 120 degrees to 115 degrees, giving you a delta t of 38 degrees instead of 43 degrees, or about 12%, (given on a 100 degree outdoor temp), cooler days it would be even less. Even if you make the most optimistic assumptions, your savings would come out to be between about $3.00 to $12.00 a year.

When factoring in the short cycling of the air, potential of backdraft, the possibility of drawing in CONDITIONED air into the attic, making another opening in your roof that might leak someday, very low if any payback, my suggestion is to invest your money elsewhere.

This is not just my opinion. Many agencies, like the Florida Solar Energy Center, as well as the American Society of Home Inspectors, etc say basically the same thing.

I apologize for the long post. My only intent is to help by giving some industry info on the subject.

Respectfully, Frank
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  #42  
Old 07-04-2012, 08:53 PM
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FRANK............where the heck have ya been, man?

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  #43  
Old 07-04-2012, 09:14 PM
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Quote:
Originally Posted by jane032657 View Post
Are the tubes and fan eligible for federal tax credit? Or just one or the other? We are thinking about putting in six-two bathrooms, one hallway, over Kitchen Island, in living room and parallel to living room in walkway space, as well as the fan. Any disadvantages to solar tubes, i.e. is it ever too much light?
I think many of us look at homes and for some reason they seem lighter and brighter? Maybe its out positive energy and enthusiasm to move to TV.

Our house once we were in it for a day or so the wife looked at me and said, Were living in a cave! It is to dark in here.

Were thinking up to 3 -4 Solar tubes.

No tax credit for them but a tax credit on the radiant barrier and solar fans.
  #44  
Old 07-04-2012, 09:21 PM
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Originally Posted by Bill-n-Brillo View Post
FRANK............where the heck have ya been, man?

Bill
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  #45  
Old 07-04-2012, 09:26 PM
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Quote:
Originally Posted by faithfulfrank View Post
A typical Attic is designed to pull cooler air passively from the soffits up through either a ridge vent or non-powered roof vents placed close to the ridge. This natural convection works well as long as you have the proper amount of ventilation.
Agree

Quote:
When you install a powered vent, it will take air from the least resistance. This usually is from the already installed ridge vent....thus "short circuiting" the natural convection from the soffits and leaving much of the attic with less air movement.
Not saying you're wrong just want to understand, there is more sq" of ventilation area in the soffits than the ridge vents, I think you agree.
Therefore, the least resistance in not the ridge but the soffit, does that make sense?

Quote:
Worse, sometimes they can produce negative pressure from openings in the living space ceiling and draw CONDITIONED air from the interior of the house into the attic
But those openings would have to have less resistance than then the ridge or soffit I would think.

Quote:
This negative pressure could also cause backdrafting from a water heater and put carbon monoxide into the house.
That's a stretch, how about using the right size not oversized fan in the first place. Moreover, with that theory those same fumes would exhaust out thu the attic.

Quote:
Studies have shown that powered ventilation may lower the temps up by the ridge by about 10 degrees, but the temps right above the insulation show a drop of less then 5 degrees.
Can you please point me to those?

Frank, understand I think the radiant barriers are my first choice, my second choice is to seal all the duct work in the attic, than a fan if that doesn't cut it.

Great to have a professional contribute but some of us like to dig deep into silly things like this
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  #46  
Old 07-04-2012, 10:16 PM
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Dear Jimbo,
I understand what you are saying.....I do not disagree, but I think that even though there is more sq ft of sofitt perhaps, there may still be less resistance from the closer ridge vents is some cases.

As to the backdraft situation, it has actually happened and is not too much of a stretch. I've inspected many homes where just having the bath vents and exterior exhausting range hood going caused a backdraft situation on a gas water heater or furnace. You could actually see it fogging a mirror when held next to the draft vent of the heater. With homes being tighter now it happens easier then when homes were more drafty.

As you asked, here are some interesting articles on the subject of not using powered attic ventilators.....

Home Energy Magazine :: Drawbacks Of Powered Attic Ventilators
Advanced Energy
http://tinyurl.com/66qq8jv

Hope you enjoy them, they are interesting.

BTW, I think the solar tubes are great in some homes, as long as they are quality ones and installed properly so as to not cause a roof leak.

Respectfully, Frank
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  #47  
Old 07-04-2012, 10:28 PM
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Default Installation

Quote:
Originally Posted by faithfulfrank View Post
Dear Jimbo,

BTW, I think the solar tubes are great in some homes, as long as they are quality ones and installed properly so as to not cause a roof leak.

Respectfully, Frank
Frank- I love you man!
  #48  
Old 07-04-2012, 10:30 PM
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Quote:
Originally Posted by faithfulfrank View Post
Dear Jimbo,
I understand what you are saying.....I do not disagree, but I think that even though there is more sq ft of sofitt perhaps, there may still be less resistance from the closer ridge vents is some cases.

As to the backdraft situation, it has actually happened and is not too much of a stretch. I've inspected many homes where just having the bath vents and exterior exhausting range hood going caused a backdraft situation on a gas water heater or furnace. You could actually see it fogging a mirror when held next to the draft vent of the heater. With homes being tighter now it happens easier then when homes were more drafty.

As you asked, here are some interesting articles on the subject of not using powered attic ventilators.....

Home Energy Magazine :: Drawbacks Of Powered Attic Ventilators
Advanced Energy
http://tinyurl.com/66qq8jv

Hope you enjoy them, they are interesting.

BTW, I think the solar tubes are great in some homes, as long as they are quality ones and installed properly so as to not cause a roof leak.

Respectfully, Frank
D0 you think the Solar Guys are a quality product and just to summarize as I do not understand all teh psts, is a solar fan a goo or bad idea? Just basic language for me please.
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  #49  
Old 07-04-2012, 10:54 PM
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Quote:
Originally Posted by jane032657 View Post
is a solar fan a goo or bad idea? Just basic language for me please.
Frank says no Carguys says yes, I think yes, but the first thing to install is a radiant barrier in the attic, if not satisfied then the fan.

But if I install a fan it will be ducted down near the attic floor to mitigate any short cycling.
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  #50  
Old 07-04-2012, 10:57 PM
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Quote:
Originally Posted by jimbo2012 View Post
Frank says no Carguys says yes, I think yes, but the first thing to install is a radiant barrier in the attic, if not satisfied then the fan.

But if I install a fan it will be ducted down near the attic floor to mitigate any short cycling.
My understanding is a cooler attic is a cooler house? No one is hanging out in their attics so I am just trying to ascertain the exact reason to put anything in the attic to keep it cool, aside from obvious reasons to keep air circulating to maintain the things you keep up there? I am getting a little lost on this discussion and I scored 15/100 on mechanical reason so I am struggling with all this.
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