We had a similar need, but only because I did not want the hassle or visibility of cutting into the ceiling to install a whole house fan. what I came up with after much searching has been a PERECT solution for us. It is a window mounted whole house fan. I did not have any thought that it would actually move air in the same quantity as the conventional whole house can. It is MARVELOUS! I am pasting the url for the site from which I ordered ours.It has been two years now and I would never be without it again. They install in any conventional window of reasonable size (see site instructions), and attach only by 4 little screws into the inside of the facing and do not show. They have switches that can be turned to either sucking or blowing so you can vary the pull either way. The window can shut down behind the fan for rain or winter. And it draws air in a major way. We have saved scads on electricity bu using it when the nights are cool enough to leave it on all night and then close up in the day. The AC will not come on for hours or even at all, of course depending on how cool it got and how hot it reaches in the day. We love VERY cool air so can tolerate it getting down to 62 or so at night to keep it from getting very hot the next day. That would all be determined by your own tastes.... They were out of stock when I ordered and so I had to wait a couple of weeks, but the company shipped promptly once they had them in stock. I am so glad we went that route! Check it out.

Here is the url: http://www.rewci.com/20wholhouswi.html

Thanks. Never heard of that solution, certainly worth considering.

I do have a few questions: Where do you live (city/state)? Does it seem to matter which side of the house you mount the fan?

I can't answer your question, but wanted to suggest that you try the Gardenweb's Heating & Air Conditioning Forum. Lots of experts there. You could either post your question there, or do a search on that Forum for "Whole House Fan". I did that for you, and came up with 21 threads.

Here is a link that might be useful: Search Results for Threads on Whole House Fan

We live in the Shenandoah valley of VA, a reasonably mild place. According to directions, you place it wherever you wish. As I said, it can be turned on to suck or blow, so it is totally at your discretion. It is easy to move so no problem to choice poorly and then fix it. You would never see the small screw holes if you changed windows. We have it in our bedroom window and use it to kill road noise as well but the noise it makes would probably annoy most people. Choose to have it in a spare room or in the master. Upstairs is obviously best. We have it blowing out, bringing cool air through our upstairs and our bedroom and also using the air to blow any small shower that might come up. It does BLOW on high and even on low so it moves a LOT of air.I assume you found it on the url??

I'm in the same boat, I don't have an attic to install a WHF. I did find a fan by QuietCoolfans http://www.atrendyhome.com/qufanromoqc.html that vents directly outside. Personally, I'm not about to mess with my roof, so I was hoping to use this on the side of my house. I emailed them but haven't heard a response and their phone # goes to VM. In the meantime I ordered the Air King 9916 20" window fan. I didn't realize this fan was made for double hung windows and I don't have a single one. I will need to setup some barrier to fill out my sliding windows.

Thank you all for the suggestions. Don't know why I didn't think to go to the Heating and AC Forum first.

I have done some reading about the window fan suggested by greengirl -- that does sound like a great idea. I gather the fan is a bit noisy, but tolerable. Several years ago I bought a bathroom exhaust fan/light/heater from that same outfit from which she bought the window fan. When we opened the unit to install it, we discovered that it was damaged; it was replaced quickly and cheerfully as I recall.