 PacketeersPremium
join:2005-06-18
Forest Hills, NY
kudos:1
 ·Time Warner Cable
 ·Verizon Online DSL
4 edits | reply to Ken Peterson
Re: Fan in window - blow in our out? just some practical advice to apartment dwellers about fans;
if you live in a building where some windows face out while others face alleyways,
know that in general alleys have slightly lower air pressure than building faces. *
this means fans should blow into building face windows and out into alleys.
I discovered this when deciding how and were to vent my kitchen hood fumes.
another reason has to do with cigarette smokers outside your apartment.
smoke is more likely to build up in alleys than building faces where it has
much more room to blow away and dissipate. so again, fan in on flat
sides of a building, fan out into enclosed areas like alleys and courtyards.
for this reason, it's prudent to buy an apartment where the bathroom windows
face an alley, not a flat building side - so the odors can flow out your window,
not back into the rest of your apartment.
* this may happen as wind passes by your building, a slight vacuum pocket
occurs in the narrows spaces between and around the exterior of each building,
since the air on the exposed sides is moving faster than the alley way air. |
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 The PigI know you want to be mePremium
join:2009-09-11
1 edit | reply to horsemouth
Need 2 fans
One in the front blowing one direction and the other in the back blowing the other direction, or Vice versa! |
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WHT
join:2010-03-26
Rosston, TX
kudos:5 | reply to scross
said by scross:said by UHF:the age old question, are you supposed to blow or suck? And the obvious answer, of course, is to try both and see which one you prefer! I find that answer, ahem..... hard to swallow.  |
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 KoilPremium
join:2002-09-10
Irmo, SC
kudos:1
4 edits | reply to Ken Peterson
Jeez...lotsa weird info in this thread.
I have surmised that I need to have 2 fans, blowing into the alley on Sunday when its sunny and when there is a breeze, to get more sucking / blowing across the sweat so I can feel the cooling that isn't really happening in the room. |
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 nunyaWho is John Galt?Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:8 | reply to Ken Peterson
I'd just buy a damned air conditioner. F___ it! |
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| reply to Ken Peterson
I think it's better to create positive pressure in the house, instead of negative (sucking air out). The reason I say this is that you have control of the source of the air being forced in. From the north, shaded side of the house? From the side where the lawn was just watered?
If you suck air out of the house, the replacement air could feed from the hotter, unshaded side of the house. And, from hundreds of small non-airtight places like electrical outlets (on walls that are receiving sun), and gaps around ceiling ductwork (pulling slight amounts of attic air in?). Cooling the inner walls and attics at the expense of the living area?
Maybe it's a small thing. But, I lay awake at night obsessing about these things.  |
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 seaquakePremium,MVM
join:2001-03-23
Millersville, MD
 ·Verizon FiOS
| reply to The Pig
said by The Pig:Need 2 fans One in the front blowing one direction and the other in the back blowing the other direction, or Vice versa! I have 2 window fans upstairs for our 4 bedrooms. Both fans are set to blow in. This increases the air pressure and forces the hot air to exit through non-fan windows. If the fans were set to opposite patterns, the net effect would be equalized air pressure and the air not with the flow pattern of the fans would hardly be affected. IF I was cooling a single room, one in and one out may work. |
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 AVDRespice, Adspice, ProspicePremium
join:2003-02-06
Onion, NJ
kudos:1 | reply to Chinabound
said by Chinabound:Having the fan(s) blowing the air in has always cooled a room much faster than using them to exhaust hot air out. it just feels cooler.
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standard disclaimers apply. |
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ke4pymPremium
join:2004-07-24
Charlotte, NC | reply to ElminsterOld
This was the FIRST thing that crossed my mind when I read the header. |
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The PigI know you want to be mePremium
join:2009-09-11 | reply to seaquake
said by seaquake:said by The Pig:Need 2 fans One in the front blowing one direction and the other in the back blowing the other direction, or Vice versa! IF I was cooling a single room, one in and one out may work. Isn't that what the OP said he wanted to cool off - 1 room?
said by Ken Peterson:Imagine a single upstairs large room in a finished garage with windows on the front and back. |
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 ParogadiWhat? Stop Looking At Me Like ThatPremium
join:2003-03-31
Racine, WI | reply to Ken Peterson
What side has sun when? I've always used fans in a push pull configuration, the cooler side is pulling air in, the hot side has the fan blowing out, switching depending on where the sun is.
If it's cool in the mourning close the windows and draw the shades too keep that coolness throughout most of the day. I.E. got the house to 73f by 7.a.m. knew it was going to be 85f by noon. Kept the house from hitting 85f till 3:30p.m.
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1 edit | reply to Ken Peterson
Re: Fan in window - blow in or out? Thanks for all the input, folks. It's understood about the various variables that can come into play. All things being equal, without the variables like the wind flow, sun, all that stuff. Just imagine it was a calm evening. I think there is more of a nod for exhausting than to blow in. The best idea is one to blow in and one to blow out, but there is only one fan. |
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 Nick_LPremium
join:2003-01-22
Pittsburgh, PA | reply to Chinabound
Re: Fan in window - blow in our out? said by Chinabound:A door is opened on the opposite end of the outbuilding allowing for exhaust. It seems to me a fan blowing in cooler air is not only exhausting hot air out at the other end, but it is also cooling the warmer air exposed to the cooler air being blown in. Does that make sense? |
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Nick_LPremium
join:2003-01-22
Pittsburgh, PA
1 edit | reply to Chinabound
said by Chinabound:A door is opened on the opposite end of the outbuilding allowing for exhaust. It seems to me a fan blowing in cooler air is not only exhausting hot air out at the other end, but it is also cooling the warmer air exposed to the cooler air being blown in. Does that make sense? No, it doesn't. You need to remember two things: 1. you cannot create cold, you can only remove hot and 2. energy can neither be created nor destroyed. The cool air blowing in cannot "cool" the warm air, it can only displace it. The benefit of the fan blowing in is the stronger directional air movement causing increased evaporation on your skin, making you feel cool (that is, after all, the main reason we sweat, to move heat). The benefit of an exhaust fan mounted high is that you can have multiple sources of "cool" are coming into your space from different ends of the house/building causing it to seem as if the entire building is getting cooled more quickly. One other thing to consider is the "chimney effect". Warm air wants to rise. As it does, it pulls the air behind it. Get that air moving with the help of an exhaust fan and get your incoming air from as close to the ground as possible you can actually get a "stack effect" going that would be greater than the fans physical ability alone to move that volume of air.
Edit: To summarize- Cool a building, face the fan out (and place it as high in the building as possible). Cool yourself, fan faces you. |
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| reply to Ken Peterson
Re: Fan in window - blow in or out? Got bugs? If so then always face the fan out. A few lucky screen sized bugs always find a way through the screen. A fan facing in will drag lots of them through. |
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 NYR 56Premium
join:2000-12-05
Smithtown, NY | reply to Nick_L
Re: Fan in window - blow in our out? said by Nick_L:said by Chinabound:A door is opened on the opposite end of the outbuilding allowing for exhaust. It seems to me a fan blowing in cooler air is not only exhausting hot air out at the other end, but it is also cooling the warmer air exposed to the cooler air being blown in. Does that make sense? No, it doesn't. You need to remember two things: 1. you cannot create cold, you can only remove hot and 2. energy can neither be created nor destroyed. The cool air blowing in cannot "cool" the warm air, it can only displace it. The benefit of the fan blowing in is the stronger directional air movement causing increased evaporation on your skin, making you feel cool (that is, after all, the main reason we sweat, to move heat). The benefit of an exhaust fan mounted high is that you can have multiple sources of "cool" are coming into your space from different ends of the house/building causing it to seem as if the entire building is getting cooled more quickly. One other thing to consider is the "chimney effect". Warm air wants to rise. As it does, it pulls the air behind it. Get that air moving with the help of an exhaust fan and get your incoming air from as close to the ground as possible you can actually get a "stack effect" going that would be greater than the fans physical ability alone to move that volume of air. Edit: To summarize- Cool a building, face the fan out (and place it as high in the building as possible). Cool yourself, fan faces you. Your summary seems correct - I agree that the best theoretical method is to exhaust hot air from the top. However, the initial statements about thermodynamics are not particularly related. The cool air IS "cooling" the room, albeit by absorbing the heat from the hot air. Whether we view this as heating the cool air or cooling the hot air is irrelevant for our purposes. The main issue, as you said, is that intake will be more prone to mixing with the hot air and pushing out a lower temperature air through other sources than exhaust, which is more likely to push out the hottest air and pull in cool air.
That said, whatever feels better is what you should do. I'd rather sit in an 80 degree room with a fan blowing on me than in a 79 degree room with a fan sucking air from me. |
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| reply to Ken Peterson
Re: Fan in window - blow in or out? This is like glass half full or half empty. It really doesn't make much difference. The fan creates a slight temperature rise, get a high resolution thermometer, and probe the intake and exhaust sides of the fan in action and you can detect it, so blowing out would be more efficient.
But regardless of if you blow in or out, you are changing inside air for outside. If you blow it out, it comes in the other windows, if you blow it in, it goes out the other windows.
Blowing in has the potential benefit of stirring the air in the room up more due to higher turbulence.
Both have benefits and drawbacks, so just do whatever you like, and if you don't like it, turn the fan around! |
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| As you can imagine, this came from a difference of opinion of a friend and I at his brother's house. He wanted the fan to blow in to get rid of heat and I felt it would be better to exhaust the heat the the parameters set forth above (calm evening). He couldn't believe I would do that. He refused to see that exhausting the heat (with two opposite windows open) might be more beneficial than blowing the cooler air in from one source. It sounds like 6 or 1, half dozen the other. I still think I had the better idea. (don't we all?) |
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1 edit | reply to Ken Peterson
For me, it depends on how hot it got during the day.
In the bedroom, I have a reversible fan, which I like blowing in during the night. Don't usually use it at all during the day. Don't want it sucking in warm air.
In the living room I have it blowing out, with bedroom door open, so I'm getting a slow draw through the entire house.
In your case, I would probably have it blowing out all the time.
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| reply to UHF
Re: Fan in window - blow in our out? Let me ask her but mouth is full... LOL!!
(ok, that was bad...I sorry...) |
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