On Apr 17, 2:27*pm, "HeyBub" wrote:
BobR wrote:

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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.

There are at least two exceptions.

1. If the wind is blowing parallel to the ridge vent, no suction.

2. If the wind is blowing perpendicular to the ridge vent, as much (or more)
is blown INTO the ridge vent as is sucked out.

All in all, I suspect it's a push regarding wind and ridge vents.

Do some research on the subject and you will see that is not the
case. Its a rare case the the wind will be blowing directly parallel
to the ridge but even if it is, it will reach some point of leaving
the roof and will thus draw a low pressure. As for the perpendicular
blowing as much in as is pulled out, that is not even close to the
case. The low pressure on the back side will far exceed any air blown
in and the air blown in will be directed directly out the other side
increasing the pull on the air in the attic.

A machinist friend of mine once got a contract for producing a vacuum
pump that used compressed air. It operated on what I believe they
term the venturi effect. The compressed air was released at a point
where it pulled additional air from the vacuum feed line. The
resulting low pressure zone would pull a complete vacuum on a 55
gallon drum in a matter of seconds. It was amazing to see how
effective it was.