@H…can’t tell if you are
@H…can’t tell if you are being sarcastic or not but while UV does more damage to things (including skin), IR is where more heat is transfered

btw ethan…i hope you
btw ethan…i hope you blocked off the area of the gable vent outside the fan shroud. this really adds to the efficiency of the fan. otherwise a considerable amount of exhaust air bounces off the louvres and comes back into the attic short cycling the exhaist air

Also – construct/purchase an air-tight box cover for your whole-house fan to seal it off from the living area when not being used (did this at my dad’s). Alternatively, you could get one of those thin bubble wrap/vinyl panels with hook-and-loop fasteners to cover the attic-side louvers (did this at my brother’s). You will be amazed at how much this will add to your comfort.

Reminder: I am in Oregon, very dry so no humidity problems. We run the AC rarely, but recent tests have been with it on (forecast highs > 95 degrees). The attic has fairly good soffit venting and limited turtle vents just below the ridge. We have a whole-house fan as well. The attic is reasonably well insulated the ceiling is not well sealed.

Our overall strategy is the same before and after: open the house at night and run the whole-house fan for a while evening and early morning, then close everything down and leave the circ fan "always on" with the AC set somewhere in the 76-78 range.

Before gable fan: on a 95-degree day, starting from whole house under 70 degrees thanks to the cool nights and whole-house fan, by mid-afternoon the AC was running constantly and was unable to keep to the set point. Upstairs would get uncomfortably hot with radiant heat (ie stayed uncomfortable for some time even after the WHF ran for a while) and the thermostat (downstairs) would peak in the low to mid-80's.

After gable fan: on a similar day/start point, the upstairs stays comfortable and the AC can maintain the setpoint. There appears to be far less radiant heat upstairs—it is always comfortable and just a few degrees warmer than downstairs, but no noticeable radiant heat.

Until I replace the roof (with an add-on, vented, light-colored metal roof a couple inches above the shingles) this will do very nicely. The real solution IMHO is not more insulation (which is good, but which is solving a problem that would better be entirely avoided!) It would be better to reduce heat loading into the attic at all, which the new roof will do very effectively.

Is it drawing some conditioned air into the attic? Undoubtedly. Is it increasing the cooling load by doing so? NO, because I know the AC was running full-tilt before and failing, and now it works (and even cycles). This was a good tradeoff.

YMMV. Not a solution for Georgia 🙂

typically, tho not always,
typically, tho not always, there is a screen on the inside ite the gabe vent. this keeps out birds, bats,some insects, etc. the atea of the screen must also be subtracted

john, your statement is
john, your statement is incomplete and this all to common of a practice causes confusion amongst some readers. in some cases (maybe most) an attic fan can pull (some) air from the house to cool the attic . an attic fan can by no means pulls all the cooling air from the house as your statement could be read to mean tho i am sure that is not what you meant.

in my limited experience of a gable mounted fan, its installation resulted in the home being 8F cooler upon returing from work (~5pm) WITHOUT the A C on

Gary,
Gary,
You should really quote what information you are referring to. A general statement that you are making, without a reference, is vague, or at least state the persons name you are referring to their comment.
I could do the same thing you're doing without a reference point: As far as I've read and learned, the problem isn't that you can't cool your attic, the problem is you are cooling the attic with the air from inside your home. I can prob provide you with a minimum of a dozen quotes from within this page that state this.

Thanks Skye,
Thanks Skye,
So, my width is 18in and each louver has a 1 inch opening, but there are 7 of openings. So, my net free area for one gable vent is 18in x 7in =126 sq in?