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?

--
Steve Bell
New Life Home Improvement
Arlington, TX USA