# Case Airflow, are side fans bad?



## JLV2k5

I saw this in a case article.

Things to Avoid
The following are things that will actually hurt the performance of your computer.

> A side fan.  It looks great on paper, right?  I mean, how can having another fan not be good for your computer?  Let's consider the two scenarios.  If the fan is blowing air into the case from the side, it disrupts the smooth front-to-back airflow that's already there.  And if it's sucking air out, it's taking air away from the CPU, which means the CPU fan has to work harder to get the same amount of air to the CPU.  Neither of these is better than what you already have without a side fan.

Is this true? I know some people with the Antec 900 actually installed a side fan in the clear vent of their case. Is this a bad thing to do, as seen above? A test may be required to prove this.


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## taylormsj

Its good, but if you have a H/S that blows air out the back of the case, then you dont want a fan on the side of your case if it is quite high up on the side, in the middle is good. 

ALso, huge side panle fans (250, 360 etc...) are bad, i had one, they completly screw air flow


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## JLV2k5

Yeah i cant imagine the huge ones being good. I had heard of ppl adding a 120mm to the side of an antec 900 and being fine. 

Don't most stock HSFs blow air directly up towards what would be the side vent?

I know some Zalman setups blow air along the MB.


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## taylormsj

Any heatsink that doesnt blow to the sides (or to the roof) are most probably not worth it! And stock heatsinks push air down onto the heatsink they dont blow upwards to a side vent


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## JLV2k5

taylormsj said:


> Any heatsink that doesnt blow to the sides (or to the roof) are most probably not worth it! And stock heatsinks push air down onto the heatsink they dont blow upwards to a side vent



What you said does not make sense. Are you saying that all stock heatsink fans blow the air into the CPU HS and are not worth it?

I know stock HSFs work, I have been advise to use them if I am not OCing.


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## taylormsj

Yes, every stock heatsink i have seen blows air down onto the heatsink, it doesnt pull air off it !!! And yes, these are poor, and any after market heat sink that doesnt blow through the heatsinks fins and out of the case cant be good for case air flow !


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## JLV2k5

Yeah that is true. Should i really invest in an aftermarket HSF if i am not OCing though?


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## footballdude2k3

with all of the airflow in the 900, i would think that you would be fine on stock everything else


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## JLV2k5

Haha. Thanks, thats if i get the 900. Did you order yours?


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## tidyboy21

I have a 250mm side fan which works great. With out it idle CPU temp was 26c, with it 21c. Northbridge temp also went down.


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## nffc10

My temps load around 5/6C lower with a fan in the side blowing air in. It's only 80mm but it works a treat.


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## JLV2k5

nice, thanks for the input.


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## nexolus

If you have a good airflow from front to back, no amount of sidefan will stop the air from continuing backwards.


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## Dr Donut

I have always used a sidefan in my cases and think that they actually help air flow due to the fact that temps have dropped, I know this could be because theres more air on the chipsets, etc.. but the temp of the air in the case decreases to but thats just my take


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## WhiteFireDragon

yes it side fans mess up airflow, but they also circulate and move air around, so it's a pretty even, if not better, trade off


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## apj101

i mess yeti


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## ride3k

I think the best idea is a front low intake + rear high exhaust + mid side intake + rear roof exhaust.  if you think about it the two intake streams will merge and then split at the exhaust fans


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## vonfeldt7

soooo what about the XCLIO Windtunnel. All it has is side fans lol. This would still be a decent case right? (I'm assuming so, because there's no front to back airflow for the side fans to disrupt)


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## OvenMaster

The only fan my POS came with originally was the fan on the PSU. Sheesh. I added a rear exhaust fan, a side case fan blowing in at the lower right near the front of the PC, and direct-ducted the fan on the CPU. Even when running Folding@Home, on the hottest days the max CPU temp with the stock heatsink is no more than 47°C and the case gets no hotter than 38°C. Even the hard drive temps dropped, which is a good thing.

The bad part is that now the computer sounds like a vacuum cleaner when it's running, and the air filters for the CPU and side fan get filthy real fast.


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## Yeti

apj101 said:
			
		

> i mess yeti


I hope that's a typo; I don't want you to mess me . I've been gone a bit, but I try to check here sporadically.  The next two years though I'll be pretty much gone due to training if everything goes to plan. 

As for the topic at hand, it's a bit too much of a generalization to say that a side fan is always good or bad.  There's so many factors that it's really a case by case scenerio.  The strength of all the fans, the position of the fans, the size of the case, the HSF, hard drives and other obstructions all play a role in the overall airflow in the case.  Of course you want to avoid opposing flows and mixing streams, but in many cases even that can be fixed with a little makeshift duct work.  If you're really concerned about it (and don't have a CFD program and lots of spare time), just change things around - turn fans on/off, adjust fan speeds, try some ducting - until you get the lowest temperature.  If you're really a geek you'll find a way to put it in a spreadsheet and make charts and graphs of the results


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