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You want good ventilation no matter your clime . . .

If you've got adequate soffit / ridge or gable vents; I can't see what such a fan would have to offer. If you haven't got good ventilation up there for whatever the reason; then it would help. You must remember however; that if you try to suck air OUT via the fan; there must be an equal amount of air coming IN . . soffits vents or such.

Not needed if you have proper ventilation in the first place . . . though it may not do much good; can't imagine it would do any harm . . .

Bob

We installed one on our last home and it made a considerable difference. While I agree with the previous poster regarding the need for adequate ventilation, the solar attic fan moves as much as 800 cfm of air actively. I seriously doubt that you would be able to achieve that with a passive ventilation system.

The biggest issue, imo, is whether or not you have an attic space to ventilate. We had a partial attic upstairs (over 3 bedrooms). We recommended the solar attic fan to neighbors who had considerable more attic with direct Western exposure. They ended up installing two fans and greatly enjoyed the results from the standpoint of comfort and reduced cooling costs (a/c didn't have to work as hard without a hot attic).

We also installed a whole house attic fan (to remove hot air from the house (we did not have/need a/c)). This was optimally used when the outside air temp was 10-15 degrees cooler than the inside. In California we had plenty of cool evening breezes but the inside of the house would take a long time to cool (with out the whole house attic fan).