I can only tell you that my computer is standing in a dust free area / room, the temperature in this room is around 19/20C.
I use 3x 120MM Noiseblocker eLoop B-12 PS as front intake on 800rpm (really quiet and enough air movement). I know these fans are PWM. But I prefer them on a fixed 800rpm.
I use 2x 120MM Noiseblocker eLoop B-12 PS at the top of my case attached to my H100i V2 radiator. I have placed them above the radiator and not beneath.
This will make sure the air will get pulled through the radiator correctly and will not leave any hot air.
I use 1x 140MM Noiseblocker Casefan eLoop B14-PS as rear fan to exhaust on a 800rpm.
I also make sure that i un-dust my case every week with a compressor.. this will take me 2 minutes. Make sure you have your fans locked.
Don't let your fans move when you blow air in.. this can cause really bad damage.
That's the secret.