The idea includes gaps where the roof meets the ceiling, so air is drawn from outside.
> If you aren't using A/C and have the windows open, then it only helps, of course.
I make use of the "stack effect" to cool the house down in the evening. Not even a fan is necessary.
One mistake I made was to not have the A/C pull from the basement, which is always 10 degrees cooler than the rest of the house.
> The idea includes gaps where the roof meets the ceiling, so air is drawn from outside.
Of course you should have soffit venting, but forced ventilation results in negative pressure, regardless of whether that venting is a cupola harnessing the wind or a motorized fan. That negative pressure will pull conditioned air out and building science research shows higher attic temperatures are better than forced ventilation.
Even better is larger amounts of passive ventilation, but if the only thing you change is adding forced ventilation, then you're creating negative pressure and this is worse if using A/C.