Ask HN: Do I place the fan so that it blows air inwards or outwards?

Post by heavenlyblue » Mon, May 28, 2018, 4:49 PM UTC

realpeopleio wrote: post #77

realpeopleio wrote: post #37

My 4rd grade teacher was convinced of the science of using two fans to cool off the classroom: one blowing cool air into the classroom from the hallway and one fan blowing hot air out of the classroom through a window. The kids that sat near the fan blowing in the room from the hallway were quite content, but the kids by the window were always complaining and they would secretly turn the fan in the window around so i…

I should add that my teacher would think we couldn't understand the science or concept behind airflow going through the classroom to cool us off. He'd explain it over and over and get frustrated that so many students didn't seem to "get it." But really they did get it, it just wasn't working for them. I wonder if the arguments about scientific things nowadays aren't similar. It may not be that someone is stupid or do…

Post by spdustin » Mon, May 28, 2018, 4:59 PM UTC

m0rose wrote: post #87

colanderman wrote: post #83

Earlier quoted context omitted.

I strongly disagree on the setup with only one fan. Having only an exhaust fan in the room will draw nasty air in through cracks in the house's structure, possibly stuff with e.g. mold spores. My wife could never remember which way was which for our window fan; I could tell by smell when she had left it exhausting for more than an hour. If you have only one, set it to intake and leave another window open a bit (maybe…

Agreed. In my own experience, it's much more effective when cooling a room to pull the cool air in than to try to exhaust the hot air from the entire house so that cool air will eventually trickle into the room you're trying to cool. Changing from pushing the air out to pulling it in directly was an epiphany for me when I was younger and lead to many nights of better sleep. Even better, now that I own my own house, i…

Post by saalweachter » Mon, May 28, 2018, 5:15 PM UTC

colanderman wrote: post #81

kenhwang wrote: post #28

Earlier quoted context omitted.

Just to add, for computer cases, you want it to be a high pressure zone because intake fans generally have filters in front to catch the dust before it gets into the case. Negative pressure means dust gets sucked in from the cracks.

Same applies for house fans -- you want the intake fan to be slightly stronger than the exhaust fan. Else the negative pressure will draw outside air in through cracks and all the fun smells that come from those places. (I have a combination energy recovery ventilator/HEPA filter that has has a restriction filter on its exhaust for this reason. Else it would just suck crappy air in from the basement instead of fresh…

Post by Steel_Phoenix » Mon, May 28, 2018, 5:39 PM UTC

neltnerb wrote: post #89

cbanek wrote: post #9

Like others have joked about, it's really about where you want the air and temperature to go. Let's say you have three fans in a computer case, one at the back, one at the front, and one on top of the CPU. If they all blow out of the case, then you've basically created a negative air pressure zone, and you will be sucking air through the vent holes elsewhere, and through any gaps in the case. This may have effects fo…

Height is also important if you've got a multi-floor house. In upper stories, make the fans face outward and on the ground floor make the fans face inward and you'll set up a continuous air path throughout the whole house favoring cooler air. Personally for a single fan in a smaller room where you're near the window, I'd say just point it in. That way you get fresh air right where you are sitting, you get the breeze,…

Post by mark212 » Mon, May 28, 2018, 8:25 PM UTC

spdustin wrote: post #103

m0rose wrote: post #87

Earlier quoted context omitted.

Agreed. In my own experience, it's much more effective when cooling a room to pull the cool air in than to try to exhaust the hot air from the entire house so that cool air will eventually trickle into the room you're trying to cool. Changing from pushing the air out to pulling it in directly was an epiphany for me when I was younger and lead to many nights of better sleep. Even better, now that I own my own house, i…

In some zones, whole-house ventilation fans (which are installed in the ceiling below the attic) are excellent and efficient ways to cool and/or ventilate a house quickly—by exhausting the air in the living area of the house up and out through the passive vents in the attic. Open some windows, turn on the whole-house fan, and the air in the house is fully exchanged with fresh air from outside very quickly. It helps t…