Ventilation Fans pt 2
wisdom would seem to be against using fans for venting the heat
out of the roof, particularly during summer months as regards
to operational life and efficiency of the fan.
there is nothing to prevent you from using a fan(s) for air
ingress (eaves) into the roof space as the ambient air flowing
over the motor is never going to be critical and as long as
the roof ventilator does not create too much resistance so as
to cause the fan motor to overheat, then it could be considered
an alternative in creating a positive flow in ventilating the
heat out of the roof space.
In all cases
the roof ventilator needs to be able to cope with the flow required
to ventilate the roof efficiently and the duty of the fan needs
to be proportional to the release as a pressurized roof under
these circumstances is something to avoid.