i have an atx case with 4 open windows on the left and 4 on the right side, each window is 30cm x 10cm, i have put mesh on the windows to prevent dust as possible, however i would like to know since my case is kind of with open sides, which would be better a positive or a negative air pressure?, and where to put fans please?
I have ALL fans blowing IN as in INTAKE...EXCEPT for EXHAUST...your exhaust will be as close to the top as possible...ie..top back of the case OR top mounted fans blowing out...heat naturally rises...all the components inside the case benefit from the greatest amount of cool air entering the case as much as possible and with a top mounted or back top mounted fan of 120MM or bigger..140MM better...200MM BEST...whatever you can squeeze in at the top portion of the case should be the ONLY exhaust...
I've built numerous rigs both AMD and INTEL...and this seems to provide the coldest motherboard component temps and the cpu is usually mounted towards the top portion of the case...the heat generated by the cpu and voltage regulator modules...VRM's...is where the most heat is produced..well...except for the GPU...however I prefer to have ALL the heat from the cpu and vrm's to be exhausted at the top or top back of the case...that way all that heat is NEVER allowed to be circulated to the other areas of the case OR the components IN those areas!!!
The last four rigs I built were 2x Antec 1200's with AMD...and...2x Intels..one in a Antec 1200 and my current rig...BlackHawk Ultra Super Tower...ALL configure as I just described...I'm now up to 5x120MM side fans..intake...1x200MM side fan...Intake...4x 140MM front fans...Intake...1x120MM backside of motherboard...Intake...and 140MM top back...Intake...I have my H100 set to Push/Pull...OUT...at the top of my case...4x120MM fans mounted to it and 1x120MM fan beside the H100..ALL are my only exhaust...my temps ambient for motherboard are usually 29C...even under extreme loads...my cpu hits maybe 49-51C under 100% load for hours and hours...My GPU...xfx 6970 idles at 45C and maxes at 59-61C...has been that way for 4 months now...those temps are SO safe!!!!!
I know this is a long post but it outlines my reasoning for this particular method of intake vs exhaust and what I've found works very well!
if you want a clean case, have positive pressure with air filters in front of all the intake fans. If you want a cool case slightly negative pressure is good with most of your fans aimed at exhausting hot air from the upper/rear of your case. Air flow direction is also important. a cross flow setup from lower/front(intake) to upper/back (exhaust) is the best way about things to keep everything cool.