On Apr 17, 7:30*am, "HeyBub" 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.- Hide quoted text -

- Show quoted text -

The same mechanism also works with the ridge vents if there is wind.
The wind blowing against the roof will be forced up and over the roof
resulting in a low pressure zone on the back side of the roof. This
low pressure zone will draw the air up and out of the ridge vent even
more effectively than the wind turbine. So the result is that ridge
vents are not totally dependent on convection currents.