Whole house fans, sizing and placement?

I think the whole house fan could be a good idea but there could be some problems because of it. The air that is exhausted by the fan has to be replaced by another air source which would be outside air. You live in an area that has very hot weather and if the fan is used during the day, your house will get hotter. A better approach would be to ventilate the attic only. I am sure that the attic or roof space could easily reach 140 during the day. This temperature would not only cause heat be transferred through the ceiling into the living space but will also allow radiant heat to go into the rooms. Ventilating the attic space will not only lower your A/C costs, but will extend the life of your roof.