I'm not sure what you guys all do with your fans but silence and airflow / good temps are not mutually exclusive or anything...
Airflow is not just vents, in fact it barely is, airflow is all about case fans & RPM. Pressure and temp delta will do the rest.
I think the point is... air flow is not just about fans .
If a fan is blowing 35 cfm into a case, rest assured that 35 cfm is leaving the case ... otherwise the case would eventually explode. Since the fan doesn't have enough oomph to make that happen, the fan will just drop to near 0 ... but invariably, what comes in must go out and it does not need a extra fan to make that happen. Y ou don't need to match each intake fan with an exhaust fan. In most cases doing so will add problems.
Front .... here intakes are the best choice as a) there is no source of preheated air her and you don't want the exhaust blowing in ya face.
Rear ... this fan mount is high so ir's where aeat would collect and blows out the back away from ya face ... exhaust then.
Bottom ... same reasoning... and exhausted het would tent o rise ... sloooowly, so not hot exhaust will collect here
Top ... exhaust of course for air cooled builds but ONLY if you have enough intake fans ... 1.3 to 1.5 intake fans for each exhaust dur to air filter restruictions
Typical scenarios w/ an assumed moderately dusty air filter restriction of 25% ... all fans same model ... say package says 60 cfm @ 1.2 SP. In 'reality speak", that will meant about 36 cfm.
1 exhaust at rear .... this will suck out about 36 cfm, some of the air will enter thru front mounts, but les sbecause of the filters, most will come in thru rear grille and vented slot covers.
Add 1 intake fan .... because of filter restriction front fan will push in about 27 cfm and rear fan will remove 36 ... the remaining 9 will come in thru rear grille and vented slot covers.
In both situations, that air coming in the rear will be hotter than the front because:
a) the PSU and GFX card is pushing out hot exhaust and some of that will come in
b) As often as not, the PC is on a desk against the wall or adjacent floor will have a heat vent ... so during cooler weather ... if heat on, warmer air is coming in thru those rear openings.
Now when ya go to 2 fanbs blowing in and 1 blowing out, you solve both problems.... with 2 x 27 in (54) , ya have 36 going out so 18 cfm is blowing OUT thru the rear grilles. Now none of the heated air from heating system is coming in and no heated PSU and GFX card exhaust is coming in either. Same as using a fan in a window of a bedroom ... it's you go from two open windows (No AC) , the room will always be hotter than outside because of heat radiation on the walls, body heat, cooking electronic, lights etc.. But it s not like you need both an intake and an exhaust fan ... If the sun is setting for example and inside it's 95 inside and 85 outside, how fast the room cools will depoend on how long it takes to do an air change .... a 12 x 16 room w/ an 8 foot ceiling will do an air change in about 30 seconds with a 50 cfm fan. The heat is not stuck in the room unless of course the other window is closed. Open it and it goes out, it doesn't need an exhaust fan.
In short, the grille openings are an important part of the ventilation / cooling system ... which is why case manufacturers take the time to put them in and do the extra tooling to put vens in the slot covers. Of course w/o the fans, the grilles won't do much but they are very effective working together.
The ideal ratio depends on the Owner. With clean dust filters, your air inlet restriction (grilles, fan mount, filters might be as little as 15% ... in my youngest son's when i notice it /// I can peel a carpet off his filters .... prolly 35, maybe even 50% ... for a reasonably attentive person I'd say 4/3 ratio is reasonable ... for the average dude, I'd say 3 intakes to 2 exhausts. As long as you have more intakes to make sure you are nit sucking hot exhaust back in ya fine... whther that be 3/2 or 10/1
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