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What is the correct placement for case fans?

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Jan 6, 2005
In another thread I will be building a wooden case. However, I need to know what ways the fans really should be pointing and how many.

The easy part is the two 120mm in the back point out and the two 120mm fans point in from the front.

However I was thinking of some fans on the top as well. Should I have 1? 2? pushing air in? pulling air out?

One big fan? like a 250m fan?


Northern Senior
Apr 24, 2007
Rear and top fans are exhaust fans. Front fans are intakes. It's as easy as that.

You can have all the unrestricted airflow and cold air intakes as you want, but without the capacity to remove the resultant warm air, you're screwed.


Senior Something
Feb 24, 2004
You don't really need to push the air up since we're forcing the air to do what we want. Convection is more important with passive cooling setups.

I tend to buy/make computer cases with one or two rear 120mm exhaust fans and at least one 120 in the front. You can run more intake than exhaust and it'll keep the dust down but I tend to like running a negative delta air pressure and deal with dusting things off a little more.


Low Profile Senior
Jul 13, 2006
Since you will be making the case yourself, consider 140 mm for case fans rather than 120 mm, they will move more air with less noise (if this is really matter).


Oct 30, 2009
I saw a Silverstone vid where they used the top fans as intakes. And then I saw a review where the reviewer was in some consternation because the Silverstone cases overall cooled well.

I know this subject is reasonably well known. Thoughts?

I'm not trolling. I'm working on an NZXT Beta Evo, and I have some great Scythe Kaze Maru fans that work far, far better when they are pushing down than when they are pushing up.