What is the current roofing system? Is it flat? And what's it covered with? Is it a traditional 'A-framed' roof? And what's it covered with? In either case, is the roof line vented with either soffit vents or eave vents?
To partially answer your question, an attic fan is used in an attic (which you don't have.)
RE: A whole house fan, I've heard of them being installed but you have to consider a couple of things. 1) You will be venting to the outside, DIRECTLY. How will you 'protect' the fan from the outside 'elements', including rain, sun, snow, hail, and such? 2) Will you be able to install the fan in such a way to keep out bugs and such? 3) Assuming you understand how a whole house fan operates, Air-Out MUST = Air-In. How will you 'feed' the fan?
If you don't understand how a whole house fan works, even assuming you can 'handle/fix' any problems associated with the elements and bugs, the fan needs to be able to do what it's DESIGNED to do. All I'm saying is that EVEN if you can do this, you should read up on how the fan is 'fed'. If you can't meet this requirement, in spite of handling any 'problems' w/Mother Nature, I wouldn't do it.
I've only heard of someone doing what you've described doing only once. And at the time, they had no problems. I never did see the install and never got to 'question' anything. W/that, I can't say if it was a 'success'. Unless you can find a fan designed for your particular installation AND find one which can be adequately 'fed', again, I'd skip it. So, what are your alternatives?
Well, the good news is that hot air rises. The installation of a skylight or 2 may be the answer. Again, in order to 'push' out the hot air, the room(s) will need to be fed w/air. Perhaps opening a window or 2 will suffice. A screen will slow down the movement of the hot air but it won't stop it from being pushed out. And to boot, I suggest a Manually Opened window vs. one that works w/a motor. If you have a flat roof, the skylight will need an 'extension kit' to deal w/snow and water build-up. Of course, once you put holes in your ceiling, you're potentially exposing yourself to leaks. If it's a peaked roof, you MAY not need the extension kit but the potential for leaks is still there. (That's the nature of the beast.) Just be sure you have a Pro install them. Preferably, get a pro that is recommended by the Retailer. (He's gonna have to put his reputation on the line a little so you know he won't be refering you to a fly-by-night pro.)
Others may have more to say so stick around a few days. Velux sells nice skylights, and their windows come w/extension kits, if necessary. Velux.com My best to ya and hope this helps.
Jay J -Moderator