[faithfulfrank]

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