Re: turbine vents --- to install or not to install?
I put one up about 11 years ago. It was not an expensive one. It is still there. I needed it because of condensation on the underside of the roof.
The only times there have been noticeable squeaks were:
1. when it got knocked off level by a big hailstorm, and
2. occasionally in winter when it presumably got an accumulation of ice on the moving part making it off balance.
The axis is supposed to be installed vertically but I can show at least one near my place that is not anywhere near vertical and it seems to work.
They are definitely powered by the wind. I have heard one complaint that they leak, but I have no evidence of that.
A powered one might be better to cool the house on a hot, calm summer day.
It ain't the things you don't know that get you in trouble. It's the things you know for sure that just ain't so.