Since winter is coming up soon, I wanted to try pulling in the cold air from outside straight into my PC for extreme low temps. I went to Home Depot and got a dryer duct and some rigid foam insulation to put into my window so the cold air won't freeze me while I sleep. Home Depot only had 2x8 feet slabs of insulation so I have plenty.
I cut the foam to the width of my window so it can fit, then I cut a hole in the foam so the air can go through the duct. I used an old Newegg box laying around to to attach the duct to the PC case.
It was around 40°F (4.44°C) outside during this first test of PWAI, the case was COLD to touch! My 4770K cores are idling at 20-25°C. However the stock fans in my case suck and don't push much air. The 140mm fans only push 66 CFM and 0.84 mmH20 static pressure. I looked on eBay for some nice powerful Delta fans. I found the AFB1212SHE for $18 each. When they arrived, they was thick and heavy!
These babies can push 152 CFM at full speed of 3700 RPM with 14.5 mmH20 static pressure at zero air flow and they are LOUD! One of the fans had issues so I opened it up and greased the shaft and bearings up. Runs like new now. These are way overkill, so I just run them at lower speeds. However the cheap fan controller built into my case only offers 5V, 7V and 12V speeds. That doesn't give me much control over the sound and speed levels. So I made a trip to FrozenCPU here in Rochester to pick up a PWM splitter so I can safely control the fans with my motherboard PWM header while powered by the PSU.
With the PWM splitter, I can fully control the fan speeds according to temps. At idle, they just spin at ~1000 RPM, revving up to 2000-2500 RPM under load. The fans goes full speed when cores are above 80°C.
Currently, the PC gets colder when the load goes up because of the fans revving up under load. See graphs below!
These core temps are only with 40°F (4.4°C) outside air. Wait until it gets below 32°F (0°C)! Here is a comparsion with and without the PWAI. You can see a difference with min idle temps and the max loaded temps. The PC temperature follows outside air temperature.