For context, I’ve got a basement room in an old house that isn’t tied in to central air conditioning, and sometimes the air gets a bit stale.
It has a basement window, so I’ll open that up and stick a fan in the window to blow air out, but someone told me that it’s better to have the fan outside and pulling fresh air in.
The room won’t be overpressured as it’s got a big gap under the door, and the fan doesn’t cover the whole window.
In: Physics
Depends. If it’s warmer outside and you want it inside, then blow it in. If it’s warmer inside blow it outside. There’s no such thing as cold, just the absence of heat.
What id do is open the basement window, then open the door and another window in the house. Then have the fan blow out the basement window (try both, I’m not sure which will week better). Get one that covers the whole window if possible.
My parents house has this on a larger scale and it cools the whole house in like 15 minutes if its cool out
Fans like you’re talking about aren’t very good at pulling air in, they push the air from where they are (which in your case is inside). If you set it up “blowing in” it will be mostly blowing air that is already inside further inside. If you set it up “blowing out” it will be blowing air that’s inside mostly outside. Blowing out will be more effective, all things being equal. That said, it’s not always equal, if air is already being naturally sucked in with a window open, don’t fight it.
I’m assuming your goal is to cool the inside air down.
If the air outside is cooler than the air inside, it’s more efficient to open two windows on opposite sides, with the fan blowing outwards in one of them. This directly pushes the warm air out and indirectly sucks replacement air from outside.
If the air in the house above the basement is cooler than the basement or the outside air, then open one window with the fan blowing outward and open the basement door to allow cool air to flow in.
In general, it’s more efficient to orient fans to blow outward to cool homes down, but the difference is pretty miniscule.
Any mech engineers in here to answer this? I’m an EE, so no my thing. I’d think someone who had thermodynamics would be able to answer.
I’m going to take a big guess and say blowing OUT is better.
Here’s why.
Two of the homes I’ve lived in, came equipped with what we called a “[whole house fan](https://www.greencat.ninja/sites/default/files/styles/panopoly_image_original/public/lifestyle.jpg)”. It was in an upstairs hallway, mounted in the ceiling of the hallway, and blew into the attic.
If you turn the whole house fan on, it will draw air IN through any windows you have open. We would turn the big fan on, and open the living room windows, and you’d get a strong current coming into the living room.
I think blowing in is best. If you set the fan to blow out, it may be slightly better at blowing the inside air out, but the replacement air has to come from somewhere. Most likely this replacement air will be pulled from the rest of the basement, or from the house, so it will also be kinda stale. Blowing in from the window gets you air from outside directly into the room, ideally directly at you.
Blow out. Open a window or two on the other end of the house from the fan. Also get a ceiling fan going inside to prevent a single unmixed river of air flowing straight through. I usually blow out all night then blow in to the main room while I’m getting ready for work. Then close up the house to keep the cool in.
Always blowing out, fans “take” air from all direction not only from the back so unless there’s a duct to make sure the air is coming from outside you’ll be just moving mostly the same air. Blowing out creates a current that makes the air go out so it gets replaced
Look up Bernoulli principle place the fan a foot or two away from the window blowing out the air blown by the fan will draw additional air along with it as it flows out the window opening
Edit:typo
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