I didn't see this part answered yet, but 4 °F is a very small ΔT. You're not going to get much closer than that with passive cooling no matter what you do.
this post was submitted on 11 Jul 2026
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It hasn't been said but I assume you're closing the windows when the outside temp is higher than the inside temp.
We are men of science. Mentioning such trifles does not become us.
You need fans to blow the air OUT not in, and create a chimney effect between opposite sides of the building.
A small out blowing fan can be enough, if run all night.
Blowing out will cause air to be sucked in from the opposite side. Having multiple fans will only mess up the air flow and reduce the efficiency. Better two fan on the same outgoing window.
Of course, that will never cool down more than a few degrees above outside temp because walls thermal cycle will bring inside day heat at night and bring inside night cool in daytime. Specially thick or well insulated walls are designed to do exactly that.
So yes walls will warm you up at night, that is not avoidable. A well insulated wall will do that instead of bringing heat in during daytime... But heat is there and must be dissipated that's physics. Night time is the best option.
Edit: blow out at night. During daytime blow around, best way to keep cool is move that hot layer of air that get stick to your skin with a fan. Same temperatures but so much more bearable.
That's the basic theory I'm going with. Imagine a Y. Each of the top ends are two rooms with one window each. They are connected via a hallway to my bedroom on the bottom, which has two window on the opposite side of the building. The wind has the slightest tendency to blow down that Y so I have the air move in that direction.
The only wrinkle is that even with two fans in that hallway to bring the air in, there's still 3 temp difference between the top and the bottom, it gets to 1 if I flip one of those bottom fans to bring air in.
But I also have windows that open horizontally, so I have plenty of open air above the windows that I occupy with venetian blinds, so I could probably do a better job of sealing that up to improve flow and decrease backwash.
Edit: This comment brought to you by !dull_mens_club@lemmy.world
Don't forget to circulate the air within the rooms, not just move air through them. Even with airflow across the apartment, there's often pockets of air that rarely get circulated. Also, things like furniture, closets, and stuff will hold heat and warmer air.
For me, often just a ceiling fan or a fan blowing vertically from the floor in larger rooms is enough to make a big difference.
I’m guessing the walls are retaining some heat.
Guesstimate your own numbers, but the way my flat is built walls have heat capacity some 150x more than air inside. (reinforced concrete building, walls/floor/ceiling counted as half if shared with other flats) You will need to run a lot of air through, at at least couple C temperature difference, to make a dent in that
Yep. My house is block and brick and just soaks up heat all day and very slowly releases it at night. Unless there's a 20-30 degree (F) difference, it just doesn't cool down at all. It's even worse when the night time temps don't drop significantly until just an hour or two before dawn when it starts heating back up again.
That's great in the winter since a sunny day can "store" heat for the night, but it's miserable in the summer and you basically just have to pump it out with A/C.
Since fans don't cool the air at all, simply move it, your goal should be to take air from the coolest part of the house to where you are. Your 4* difference would exist with or without the fans. Rather than worry about that metric, I would concentrate on getting the moving air to where you're at so it will give you the sensation of being cooled via the moving air.
I know it is incorrect, but I read your good use of an asterisk instead of a degree sign as "four butthole".
Ok have a nice day.
It feels like roughly 120 buttholes outside.
Yup, fans are on me during the day time when it heats up. But at night, I just went to get things as cold as possible without running the a/c.
Remember to move as much of the warm air as possible at night — this means opening all your cupboards and drawers, which retain a LOT of heat. Cooling those down means they’ll help retain ambient temperature during the day instead of continuously leaking heat into the main airspace.