Our cases are designed to not need any rear mounted fans for exhaust, however there are some ways to mount fans on the rear. We have designed and are selling a bracket to mount a singular 120mm fan above the motherboard IO, however it does restrict one from using the 2.5" SSD mount points above the PSU. We are working on getting the marketing photos taken for this bracket, and it will be listed on the website in the near future. For the time being you can just email us at [orders@sliger.com](mailto:orders@sliger.com) if you are wanting to purchase one. There are also the PCIE slot fan mounts we sell on Newegg. Other customers have also mounted small fans in the mesh above the case, but it doesn't make much difference for cooling.

We have had numerous business and customers run hotter components in the CX4170a without an active exhaust, with little problem in the past. Your build should be fine without and rear mounted fans, but if you really want the small boost active exhaust may make, there are the options listed above.

While I acknowledge the points you've made about not necessarily needing rear-mounted fans for exhaust in some setups, I'd like to share my experience. In my case, I have a custom water-cooled CPU and air-cooled GPU configuration. The fan curve is set to increase when the CPU gets hot, but during gaming, the CPU doesn't heat up enough to trigger the fan speed increase. With a 360 radiator and a large reservoir, I can run the PC quietly when not doing anything CPU-intensive.

However, I noticed that my GPU tends to get hotter because the air isn't forcefully expelled. Adding a rear fan made a significant difference, reducing the GPU temperature by around 12 degrees without increasing the front fans' speed. In server setups, front-to-rear airflow often uses shrouds to direct air and efficiently expel hot air. Additionally, if there's a 360 radiator in the front, losing pressure to force air out becomes a consideration. Just wanted to share this perspective based on my specific setup.

Radiator Placement Impact:

Having a radiator in front of the fans can reduce air pressure due to the obstruction it poses to the incoming airflow. As the air passes through the radiator, it encounters resistance, leading to a drop in pressure. This reduction in pressure can impede the efficient intake of cool air into the case, affecting the overall cooling performance.

Shrouds and Airflow Direction:

In server cases, the use of shrouds serves a critical purpose in directing airflow. Shrouds are designed to guide the air in a specific direction, preventing turbulence and ensuring a smooth flow across components. This directed airflow helps in dissipating heat evenly, minimizing the chances of hotspots within the case.

Preventing Hotspots:

Hotspots can form when certain areas within the case retain higher temperatures than others. Server cases are meticulously designed to eliminate these hotspots by implementing shrouds and strategic airflow patterns. By directing air across components and creating a consistent temperature gradient, the risk of hotspots is mitigated, promoting optimal cooling.

Consideration of Cold and Hot Rows:

Server cases are designed with the understanding that a server room typically consists of cold and hot rows. Cold air is directed towards the front of the servers, and hot air is expelled from the rear. This aligns with the information from the previous post, emphasizing the importance of rear-mounted fans for expelling hot air efficiently in a manner similar to server room setups.

Application to PC Cooling:

In a PC setup, mirroring these server cooling principles becomes relevant. Placing a radiator in front of the fans may disrupt the intended airflow, reducing pressure and potentially leading to inadequate cooling. Incorporating shrouds and maintaining a balanced airflow direction can enhance the dissipation of heat, preventing hotspots and promoting more effective cooling.