Do you know attic fans?

I put one in in my former house years ago. Raised Ranch and right at the top of the stairs at the beginning of the hallway. Never needed AC. Opened the windows at dusk/sunset and it pulled in cool air and out through the attic also cooling the attic.
My Victorian home with Twenty 6foot high double sash do the same thing. Open the top and the bottom at dusk. cool air in through the bottom and rotated out the top sash. That’s why old house with double sash never needed AC either.
For a single story house this will also work well. Not knowing the floorplan, I would suggest finding a central location to optimize airflow to all parts of the house. Sleeping area airflow is key.

I love attics. Much more so than basements. Not sure I’d consider myself a ‘fan’ though.

Basements come in handy for tornadoes. :D

What size for 1200 sq feet?

A general formula of either 2 – 3 CFM, or “Cubic Feet per Minute”, per square foot of living space.
That said you would target 2500 CFM to 3500 CFM. This can vary based on the climate zone you are in. Also you need to make sure the attic has louver vents that can properly vent that amount of air as well.

Wouldn’t louver vents come with the fan?

Yes, for the units. I assumed you want this mounted in the ceiling. I was referring to the venting in the attic space to ensure good airflow. Either vented via ridge, gable, soffit, turbine, box, etc.
Apologies that I wasn’t clear.

Got cha. I don’t recall if my last house, which I owened for 20+ years, had external attic vents. As far as I know it just pulled the air into the attic where I assumed the warm air just hovered at the ceiling of the attic. It was fully insulated.
Anybody wanna see a pic of it from when it was built on 1919????

I would love to see

I’ll work on it!