I would go with Ruzumaki. I know the hot air trapped above ceiling but either you are using that power-less turbine or powered ventilation, the best result would still be the air temperature outside the house (it is higher sine rooftop radiating heat which will not be cooled down by fan sucking hot air underneath the roof.

In the case above, even if you have cooler air above ceiling, it will not provide insulation to room or hall below ceiling, thus air-conditioning will need to work harder and consume more power. With proper insulation, you do not need to care about hot air above ceiling but by doing so, it will cool down space under roof even if you do not use air-conditioning.