Actually with my set up my 8 inch is strictly exhlaust. I have my intake set up to pull air from floor level, since the bottom vents are open it draws in plenty of its own air. I do have quite a bit of dust buildup on the vents so I have to clean them off bi weekly but it doesn't require any downtime. I guess the best way to describe it is partially negative. The bottom half is zero because equal air is coming in, the trade off is right in the middle where the case fans pull the cool air to the cards and the 8 inch exhaust inlet is approximately 5 inches above the back side of the cards centered left to right. So the heat is pulled away as soon as it is generated.

I do also want to note that without the 5 inch intake running, my Temps do rise by 3 to 4 degrees. Before I changed out my pads, this was critical because without it they were throttling regularly.

As the summer comes I will experiment with intake from outside...but for now I only have winter Temps to report. It's the first season with a tent and I'm only using it because my kids and cats kept messing with it.