How Do You Orient Case Fans?


If you have ever built or modified a desktop PC in a common tower PC case, you may have wondered how to properly orient the case fans. Or maybe you didn’t really think about it, and just installed the fans without considering what you were doing. If that was what happened, maybe you got lucky or maybe you didn’t…

Making sure you orient your case fans correctly is actually very important. Doing it the right way will give you proper air ventilation though the case. This will help lower the overall temperature inside the case. Having good case ventilation will also help your individual components dissipate heat, and get that heat out of the case. This is especially important for your CPU and GPU. It also affects the voltage regulator modules (VRMs), your chipset (Southbridge), and even your storage.

For example, if your CPU is running at too high of a temperature, it will operate at a lower clock speed. This will decrease performance. The same thing will happen to your video card. The longevity of all of your components is also negatively affected by sustained high temperatures.

Installing and Orienting Case Fans

In order to get better cooling inside your case, you need to think about the direction that the air will be flowing. You want to have cooler external air entering the front of the case and the hotter air exiting the back and top of the case. Hot air will naturally rise, so you are trying to take advantage of this.

The cooler air will flow over your components, absorbing some of the heat as it does so. This will help lower the temperatures of the components. The now warmer air should flow out the back and top, as you see in the photo.

Typical Tower PC Case
Typical Tower PC Case

This same principle is used in many data centers that have cold aisles and hot aisles. The cold aisle is actually quite cold. There is heavily air conditioned air coming up though holes in the floor. The front of a rack-mount server will be in the cold aisle. There are multiple fans pulling in the cold air through the front of the server. As this cold air flows past all the server components, it absorbs heat. The air gets much warmer, finally exiting out the back of the server. The hot aisle will have hot air returns in the ceiling to get rid of the warm exit air.

What About My Tower PC?

You want the fans at the front of your case to be pulling in air from outside the case. The fans at the back and top of the case should be pushing air out of the case. The orientation of each fan controls which way the air will flow. Most case fans have small arrows printed or molded on the sides of the fan enclosure that show the air flow direction.

If there are no arrows, most fans will have the air flowing towards the manufacturer’s label that is in the center of one side of the fan housing. You can also tell the air flow direction by looking at the curvature of the fan blades. The inside of the curve is the direction the air will flow. Finally, if all else fails, just use your hand to feel which way the fan is blowing the air.

This also comes into play with the fans on radiators from liquid cooling systems. So, after this explanation, you might want to take a moment to make sure your case fans are oriented correctly!

How Do I Know If My Components Are Too Hot?

There are several free utilities you can use to measure component temperatures. A couple common ones are GPU-Z and HWiNFO64. Most motherboard vendors have utilities that let you monitor temperatures and adjust fan speed profiles. Generally speaking, once your CPU or GPU get much hotter than about 85 degrees Celsius, you will see some thermal throttling.

Final Words

Some cases prioritize aesthetics over thermal performance, with very little air flow possible because the way they are designed. Many entry-level cases may only have one or two case fans. Some economy cases don’t have any case fans.

Larger diameter fans (meaning 140mm instead of 120mm or 80mm) can move more air with less noise. Some case fan brands and models are much better than others. You want to have pulse width modulation (PWM) fans (that have four pins instead of three pins). Case ventilation and cooling is a relatively complex subject, that has a lot more detail than I have touched on here.

What do you think? Is this something that concerns you at all? Please let me know in the comments. Thanks for reading!

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