I have a Fractal Design R4 case which does have an air vent on the bottom. I have heard a lot of conflicting reviews and recommendations on which way to orient the power supply. What do you recommend? Power supply fan facing up or down??
Depends on the power supply, if it draws in more, you'll want it facing up. If it doesn't draw in much, face it down.
which ever way blows air out
I have a Fractal Design R4 case as well and the thing to consider in this set up is that in the fan down set up the PSU pulls cold air from below and exhaust it from the back of the case.
It effective remove any of it heat from getting into the case at all.
Difference is minimal in temps - really its a matter of taste and aesthetics. If you have a window and good looking PSU then fan up looks sweet....
I'm running a Fractal Define mini with the fan up and even in this smaller case it really was less than 1 degree of a difference if I have it fan down (PSU is a Corsair AX850 just for the record).
Just my 10c