Joe wrote:

Turbines are a feel-good thing like hanging strings on vent openings
so you can see if air movement is occurring. They move slightly less
air than an equivalent size open hole in the roof (think Laws of
Physics). Some folks like the industrial look, so if that's your
preference, go for it. Soffit vents and ridge vents are the modern way
to evacuate hot air, and you can't have one without the other.
Manufacturers of the products have guide lines for soffit openings
required for ridge vent effectiveness. HTH


Fiddle.

Roof turbines combine two mechanical devices into one:

1. A windmill that turns wind energy into mechanical energy and
2. an exhaust fan that sucks out hot air.

At a wind speed of 5mph, an ordinary turbine moves about 350 cu.ft. of air
per minute.

Assuming 1500 sq ft house, and an attic that's 6' high, 1500 x 6 x 0.5 =
4,500 cu.ft. / 350 = a full exchange of air every 12 minutes. Two turbines
would exchange the air in six minutes.