When I discovered that the previous owner painted over the meager number of soffit vents on my South Florida home, I knew that my attic really needed ventillation.
This was my solution:
I took advantage of the overhanging soffits. I cut a 22-1/2 x 24 hole in the front and rear of the house. I framed the holes with moulding as if it was a picture frame. I cut a piece of plywood to fit and not fall through. A hole 18" in dia was then cut into the 2 plywood pieces. A cheap pair of 20 box fans were mounted onto the plywood sheets. One fan blowing up into the attic and the other exhausting the attic. Incidentally the 3 speed Lasko fans blow at 1,2 and 3000 cfm.
The fan blowing up is at the fron of the house and is running at low speed. The exhaust at high speed. A timer turns them on at 10am and off at 8pm.
Wow! What heat is blown out. My attic now stays below 110 weras before it approached 130. The house feels cooler and thereis now hot attic smell that I used to enjoy.
FWIW.
BoyntonStu