Cooling

[xtant]

In general, it's better to have fans blowing cool air in from the outside.
I'm not an expert in this, but I'd think a push/pull setup where you have one fan blowing in on one side and another blowing out on the other side would allow for maximum ariflow, as long as the path inside the case is unobstructed by cables or cards.

[OuTpaTienT]

Generally the main fan in a system is the power supply fan and it usually blows outward from the upper/rear of a tower case. To enhance cooling it's best to add a fan to the lower/front of the case that draws air inward.

That way air comes into the case from the lower front, circulates over the motherboard & cards & RAM etc., then exits the case through the power supply at the upper rear.

Note that most cases don't allow for sufficient air flow through the front facing. This can easily be fixed with a large diameter drill bit and a drill. Make a number of holes right where you can place a fan. If done carefully this won't look bad at all. You could even make a design with the holes and be creative.

[jefwag]

I'm curious to find out what direction should case fans run: Should they blow in cool air or should they run in reverse, exhausting the hot air from inside the CPU case. I have a full tower and wanted to add some extra fans.