Secondarily, should the fan be outside or inside the window?
Asking for a friend. (Me, help. I can’t remember physics, it’s too goddamn hot)
Edit: I’ve opened all the windows and set up a fan a short distance from the window pointing out and it’s reduced the temperature to near-tolerable levels. Unfortunately, venting through the attic was a no-go but moving things aside might make it an option next time. Thank you all, I appreciate the help!
Have an fan pushing out on the ceiling in the middle of the house would work good, it will get the hottest air out. But also keep in mind: the air has to come from somewhere, if the house is sealed (new windows) this will not work well.
I’m not a physicist. But I did live in an apartment at university, and shortness of funds plus hot weather meant experimenting with various box fan configurations.
What I found most optimal was to open two windows on opposite sides of the dwelling, with the one box fan aimed outward, using cardboard to block the openings around the fan. In my case, the choice of egress (ie air flowing out) window was based on: the window which best fit the box fan’s shape, proximity of noise to the bedroom, and the quality of the window screen.
As for why the fan points outward, this sends the heat of the motor (60-100 W) out of the dwelling, rather than drawing it in. Also, if facing inward, the high airflow at the tips of the fan blades would tend to draw small flies into the dwelling. But if the fan is at the egress window, then the ingress airflow will average out over the full surface area of the ingress window, producing a lower peak airflow rate, akin to a gentle breeze.
If you have a multi-floor unit or house, it would be optimal to place the fan at the highest egress window, to take advantage of heat naturally rising. Opening multiple ingress windows will quickly cool those rooms, while also reducing the peak ingress airflow and resulting drafts (eg blowing papers off tables). Of course, it’s necessary to open all the doors to form a path between the ingress and egress windows.
Ok, so I may be way off here, but it seems to me the better of the two orientations would be to blow air out, allowing the cool air in.
As the air inside the house heats up, it will rise toward the ceiling. The fan will pull that hot air down and out the window, causing cool air to come in to replace the hot air being drawn out. And because cool air stays low to the ground, it’ll create a convection of airflow.
