I never really cared about the overall pressure of my case (NZXT Phantom) so long as it wasn't overheating and there wasn't a ton of dust building up, but now I'm beginning to get tired of the dust and my components are always cool. I calculated my CFM and found that I've got negative pressure in my case, good for cooling, bad for dust. My fans are:
140mm front intake - 62.5 CFM
120mM side intakes x 2 - 59.1 CFM x 2 = 118.2 CFM
200mM top exhaust x 2 - 103 CFM x 2 = 206 CFM
120mM rear (near top) exhaust - 59.1 CFM
Overall I've got -84.4 which seems to be quite a bit. I've got 2 options. I can disable one of the top 200mM fans to get my CFM to +18.6, or I can reverse the rear exhaust and have that become an intake bringing my CFM to 33.8.
I like having my large fans exhausting so I'd prefer to reverse the rear exhaust, but is this a common practice or is there something about it that would cause me to not want to do this? I'm going to turn it around and test out my temps when I get home, but I don't think there would be any overheating issues.