SteveBell wrote:
RicodJour wrote:
On Apr 17, 10:05 am, "SteveBell" wrote:
SteveBell wrote:
Seems like we need to replace a roof after most recent
storm in our (Dallas,TX) area.I'm thinking about putting
impact resisting shingles and since it requires
more ventilation I can't decide if I should put additional
wind turbines or have a solar fan installed instead. Our
electric bill is not that high during the summer so I'm not
sure if there is any benefit of having a solar vent + we
have plenty of wind to keep turbines rolling.
The first time you install a wind turbine, you'll discover
that the rotation doesn't actually do anything, except maybe
keep rain out. The turbine isn't fastened to a fan of any
kind, so the square inches of pipe is the only thing you need
to consider. You need to have roughly the same number of
square inches of exit for hot air at the top of the roof as
you have inlet for cool air under the eaves.
This assertion can be debunked quite easily.
Simply stand under the turbine with a stick of incense and
watch the smoke. Then stop the turbine and watch the smoke
again. In the former case, the smoke is sucked out quite
rapidly; in the latter case, the smoke goes nowhere.
A ridge vent - or hole in the roof - depends on a temperature
difference between the air in the attic and that outside to
generate convection currents.
A 12" wind turbine will move about 350 CFM of air in a 5MPH
wind, irrespective of the temperature differential.
With no wind, the turbine acts like a ridge vent, dependent
entirely on convection currents.
So what's the mechanism? How does the spinning top pull air out?
Analogous to a flywheel and utilizes the Venturi effect.
More info:
http://www.realvents.com/

I saw that page in my searching, but it just crows about how it's
"better", not explaining the physics.

Still searching since this is interesting.
I looked also. If you find a good site please post.

Lou