Whole-house fans are designed to cool the whole house. Typically, they pull air from the outside and vent it into the attic. I have one, and it is on right now. I have some of strategically opened windows around the home, opened just a crack, and the fan is doing a good job of drawing in the cooler outside air in, and pushing the hot air into the attic, through the eve vents, and eventually outside. The result is a cooler home and attic, cheaper to run than the a/c.
Of course, it is 2:30 am, and the outside air is much cooler than the house, which has been absorbing heat all day. Although I have tried various window combinations with the whole-house fan during the day, it just does not work the same as the a/c. It does cool off the attic some, but my attic is an attic, not a room. I do not believe a whole-house fan will work for you because it is designed to work with a fully breathing normal attic. Your problem could be that there is no insulation in the attic walls, or something else wrong with its design. A couple of questions:
How old is your house? Are the walls and ceilings insulated? Does it appear that the drywall/plaster ceilings match the contour and slope of the roof? Any other information you may have might be helpful as well, and I might be able to offer a suggestion.
Thanks - TomR