Originally Posted by Flamso
Fair enough! I haven't really decided if I want exhaust for the roof and intake for the rest. Dust will be a lot more problematic than temps! Thanks for the explanation ADragg!
Well the good thing about using all or mostly intake fans is that the positive pressure helps with dust. In terms of performance, you'd arguably get better performance from all intake in the roof, but fan configs really don't make a huge temp difference usually anyway. The performance probably won't be noticeable or even measurable either way, as long as there's some kind of theory to the setup (obviously you want to avoid fans working against each other and you want to avoid all exhaust because then it would likely get choked with too much negative pressure). There's the theory of convection (hot air rises) that says you want to exhaust out the back and top but while it's a small difference, I've seen people get 2-3 degrees C lower temps using the "all-intake" method in well rear-vented cases (namely the Enthoo Primo and any of the Caselabs cases).
I'm big on all intake because I prefer positive pressure as much as possible for dust reasons and because I think it might yield slightly better temps. But in your case where you're more worried about dust and already know it's not going to make much performance difference, I don't really know what I would do. If you have a filtered top on your case, then I'd go with intakes on the top because it might perform a little better and because it will help with more positive pressure which will help keep dust out even more. Plus I don't like the idea of fans blowing air out against a filter. I would think a filter would be more restrictive when in the way of an exhaust than it is when you have it restricting intake. And I also think the filter itself would introduce less noise over an intake fan. Seems like it might be noisier over an exhaust, since filters do introduce some noise, sadly.
But if you don't have a filtered case, such as a Caselabs, then I'd experiment with both options, or else just do what you like the look of better, because there'd be two schools of thought. You could say exhaust would blow up and out of the case, thus keeping dust out in that manner. But positive pressure in general also helps with dust quite a bit, and it effects the dust intake of the entire case the more positive pressure there is. And since the top of a case often has the most fans and a lot of air intake potential, it could be argued that making the top an exhaust would decrease positive pressure too much and increase the amount of dust you take in altogether. So the top as an exhaust might help a little with keeping dust from entering the top, but it might also introduce more dust in general by decreasing positive pressure too much, so you might be better off intaking from the top still. Hopefully that makes sense.