Dr. Joseph Lstiburek is an expert and is considered one of the pioneers of what's now called "building science".

His view is that the ceiling plane (between the house's interior and the attic) needs to be airtight. Any holes/gaps cause leakage of air from the house into the attic at unwanted times.

Attic fans do cool the house when running, the problem is the openings for it will also heat the house when the AC is running and cool the house when the heat is running

Here is a link that might be useful: Attic ventilation

Whole house fan is called an "attic fan" in new orleans. Most houses had them before air conditioners were invented and widely used. I grew up with one before AC and even had one in the house I am living in now, but we removed it when we remodeled 10 years ago. An attic fan mounts to the ceiling joist and the cut out was 4 times larger than the one you have... because the fan is bigger. Unfortunately it brings in the outside dirt, noise, humidity, and there is only about 2 months out of the year that it is marginally comfortable to use. But, as you said, you will save money if you are willing to turn off the AC. Before window ac units, having an attic fan was all we had..... and it was much more appreciated back then. About 90 percent of the homes in my subdivision had attic fans...thats over 2000 homes that were built in the early 1950's. A couple of nites each year we will sleep wth the ac off and the windows up..... almost like camping out.... and you would be surprised at all of the noises you hear with windows open at night. Thanks for the memory

This post was edited by henry4321 on Wed, Oct 1, 14 at 10:07