In order to optimize the airflow in your PC, it’s best to gain an understanding of how cooling works inside a computer case. This way, you will be able to set up the cooling fans the best way for any situation.

There are various ways that you can configure the fans to give you different results. So I’m going to share all of them and point out which one I recommend based on my experience after building hundreds of computers from scratch.

I’ll just mention though, that it’s easy enough to create decent airflow through the inside of a computer case and get the system temperature down to acceptable levels.

The true challenge is keeping it cool, quiet, and clean as time passes. So that’s what we will be focussing on. A complete understanding so you can configure cooling like a pro.

The main three types of airflow configurations

We will start out by taking a look at the three ways to configure cooling.

To help you understand my explanation better, here are the two types of fans I will be referring to:

  • Exhaust fan: This is the fan that has its blowing side mounted to the wall of the case. It draws air from inside the case and blows it outside.
  • Intake fan: The blowing side is facing the inside of the case and draws air from outside the case and blows it inside.

Negative internal air pressure

negative air pressure fan configuration

Negative air pressure means that more air is going out than in. The exhaust fan(s) have a higher airflow rate compared to that of the intake fan(s). And of course, we are referring to all the fans inside the case as a collective.

Examples include:

  • More exhaust fans of the same size or larger than intake fans.
  • The exhaust fan spins faster and is the same size compared with the intake fan.
  • The exhaust fan has a higher airflow rate specification compared to the intake fan.

Side note: The same points listed here can be applied to any fan configuration when comparing airflow rates.

While it is an effective way to cool your system, it can quite often result in more dust being pulled into your case over time. It is also more difficult to add filters to the intake areas of the case that specifically draw air in through them exclusively.

This is because air may be drawn in where the is no place to add a filter.

However, in some unique instances, you could have a situation where a negative air pressure configuration won’t draw in much dust.

These conditions would have to be met:

  1. There must be a large enough intake area that is filtered.
  2. The filter must have the correct pore size and density.
  3. The filter must have the correct cross flow rate.
  4. The computer case cannot have too many intake areas that are unfiltered.

If these conditions are present, it can be argued that the case may remain clean for longer periods of time.

Positive internal air pressure

positive air pressure fan configuration

Positive air pressure means that you have more air being blown into the case than out. The intake fan(s) have a higher rate of airflow compared with that of the exhaust fan(s).

While having some positive internal air pressure inside your case is a good thing, it is not the best if it’s to the extreme.

If a whole lot of air is being forced into the case with little exhaust airflow, you can find yourself in a position where not enough air movement occurs.

This results in stagnant air which can get hot from the internal components and end up raising the internal temperature of the PC.

Slightly positive internal air pressure (More balanced)

slightly positive and more balanced fan configuration

This is what I have found to be the best in terms of keeping things cool and clean. Having positive air pressure means that the air will be drawn primarily from your intake fan(s), and as I’ve mentioned, the air is easier to filter.

A standard air filter can be installed in front of your intake fan(s) if your case doesn’t have one to ensure that cleaner and more dust-free air is drawn into your case.

Because the airflow is more balanced, plenty enough air is still exhausted, which means that plenty enough air is flowing in and out.

This leaves very little chance for stagnant air hanging around to warm up and to cause the internal temperature to rise above desired levels.

How to configure the fans

Take a look at the fans that you currently have in your PC. Take note of how many intake fans you have versus the amount of exhaust fans.

If you have any that are noisy, disconnect them one at a time until the noise is gone. You will then be clear on which fans you need to replace. If a fan is noisy from a cold start up but goes quieter as it spins, be sure to replace it as it will most likely give you problems later on.

Tip: Do not disconnect crucial fans for hardware components while your computer is running, like CPU or GPU fans for example.

Assess the number of fans you need

The size of the computer case will dictate how many fans you are able to install to a certain degree.

For most mid tower cases, you will preferably want around two or three fans on the intake on the front side of your PC and one exhaust fan.

If you have a larger full tower case, three intake fans at the front and one at the rear exhaust would be a good starting point. A larger case has more areas where air can be pushed out of the case, compared to a smaller mid-tower. So I recommend a minimum of three intake fans.

Try to stick to the largest type of fan your case can support. You will be very happy you done this, later on, so you can enjoy a very quiet system.

The fan I recommend if you are needing a 120mm fan, is the Noctua SNF-S12B Redux 1200 PWM (view on Amazon over here).

Common fan sizes used in computers

Fan Cage Size (Entire Frame)Between Mounting Holes
40mm32mm
50mm40mm
60mm50mm
70mm60mm
80mm71.5mm
92mm82.5mm
120mm105mm
140mm124.5mm
200mm154mm
220mm170mm

Also, choose fans with ball bearing as opposed to a sleeve bearing, it will last much longer.

In some cases, adding an extra fan at the upper rear of the case can help with keeping the CPU cooler. Not all cases have a fan mount at the top, so it may not be an option.

Note: Selecting fans with four wires will allow you to have easier control over them. This will make fan speed control so easy from most controllers even when controlling them from a motherboard.

Configuring the fan control speeds

PC Airflow Optimization (A Guide to Setting Up Your Fans) 1
Fan with Simple External Speed Controller

There are many ways that fans can be controlled. Plenty of manufacturers offer a wide range of products to accomplish this.

If you are planning to set them up once and forget about them, simply connecting them to a pin header on your motherboard will do fine.

Most BIOS programs support fan speed adjustments that enable you to adjust the speed curve or allow full automation on the fan speed when the temperature alters inside the PC case.

This is achieved using temperature sensors to get temperature readings.

If you find that your motherboard’s BIOS doesn’t provide the configurable features that you’re after, installing a software application like SpeedFan is an option.

If you want to take things a step further, a fan controller system could be the ideal hardware component to add to the system.

All the fans connect to a module, which also connects to your power supply. The module allows you to consider each fan’s speed based on the temperature readings from the sensors.

They are commonly referred to as PWM fan hubs or simply fan controllers.

More expensive models have a firmware package that can accept programmable profiles to automatically control the fans in relation to temperature readings.

Some even offer touchscreen interfaces on an LCD display that can be mounted into a 5.25 inch drive bay slot.

How to maintain good airflow while keeping everything quiet

In our other article, we covered how you can keep a computer quiet. In essence, try and install the largest fans you can.

This might go against someone’s first thought which could be that bigger fan blades equal more noise.

While there is truth to that, there are other factors to consider. Fans are driven by motors. Motors spinning at a higher RPM (Revolutions Per Minute) can generate more noise. And the same holds true for the fan blades moving through the air.

When you use a larger fan, a greater rate of airflow can be achieved at a lower RPM. This means that fans only have to spin at a fraction of the speed compared with smaller ones to achieve the same airflow rate.

The other main thing that helps with keeping your system cooler and also but quiet, is the number of fans you use. A few more large fans spinning slowly is better that one fan spinning faster to try and achieve proper cooling.

When it comes to fan speed control, the fan is required to spin as fast as needed to keep the internal temperature of the case cool at any given temperature. So it will only spin as fast as it’s needed reducing unnecessary higher spinning speeds which generate more noise.

Rubber-mounted fans or fans with rubberized mount areas also add a little extra when trying to keep things quiet. It will lower the amount of vibration produced by the fan.

How to test the airflow in a computer case

Initially, simply using your hands can tell you a lot straight away. You can get a good idea of airflow by removing the PC case lid and feeling how much air is coming in from the intake fan(s) versus the exhaust fan(s).

Some fans have a poor design, and it may seem like they are spinning and doing their job, but the airflow can be poor. This is not ideal and I recommend replacing those types of fans right away. I found that it was most likely to happen when an extremely cheap fan was installed.

As for viewing the airflow, that’s if you have a clear case lid or some clear plastic taped to one side of the case, would be to use some incense. Use about three sticks together and watch where the smoke travels inside the case when it’s going.

The other possible option is to pick up a fog blaster from a toy or hobby shop. How well that would work though, is anyone’s guess.

If you want to get more serious about testing airflow, airflow meters are available and you can place them in various locations with your system.

Checking the air filters

PC Airflow Optimization (A Guide to Setting Up Your Fans) 2

For best airflow optimization, check that the filters on your case aren’t too thick. If they are, there is a high probability that air won’t be able to pass through them easily enough, causing poor airflow.

If the filter has pores that are too large, or if the filter is too thin, dust will easily be drawn into your machine. This will make fans, heatsinks, and the inside of your PC case dirty quickly.

Cleaning these components properly is time-consuming, that’s why careful consideration must be made to limit dust entering the system to reduce intervals between cleaning.

There are some mesh style filters that are fine but will probably mean that you will need to clean them more often. Most of the time this is fine as they are usually designed for easy removal and reinstallation.

Make sure that there aren’t any obstructions for the airflow

If you look at the airflow path inside the case by looking at where air is drawn in and where it exits, you want to make sure nothing messes with that flow path.

Hardware like cables can cause flow issues. So always make sure that the inside of the case is tidy and free flowing.

A common example of cables obstructing airflow is the unused power supply cables that often get cable ties in a bunch. This is something that is large enough to obstruct airflow and needs to be kept tidy.

Recommended graphics card cooling fan configuration

PC Airflow Optimization (A Guide to Setting Up Your Fans) 3
Blower Style (Left) vs Shroud Style (Right)

When it comes to air cooling for your graphics card(s), two main styles of cooling is used by manufacturers. One is a fan blowing on a heatsink with a shroud, and the other is a blower-style fan.

My personal favorite is the blower-style graphics card cooler. This actually takes air from inside the case and blows it outside the PCI slot plate.

I’ve found that it helps reduce the internal computer temperature substantially. However, your graphics card may run slightly hotter, so I won’t recommend this style of cooling on a card to overclockers.

If you choose to go with the more commonly used shroud style cooler, make sure your case can handle the extra heat. So ensuring that enough air flows through your case is paramount.

Tip: Do not use a shroud style card inside smaller cases.

The downside to blower style coolers would the noise and temperature. Shroud style coolers are more common and are efficient at cooling the card, but raises the internal temperature of your PC.

The graphics card is the component that generates the most heat in a PC, by far, so consider your options carefully.

If you need to know how to make sure your graphics card fans are working as they should, please read our article on how to speed up your graphics card fans.

Things to consider for water cooling

PC Airflow Optimization (A Guide to Setting Up Your Fans) 4

Having a radiator cooler assembly for your CPU is usually something that a enthusiast would desire especially for overclocking the hardware.

In this situation, I recommend purchasing a computer case that caters well for such components. If you can get filtered air being blown by the radiator fans, it will reduce cleaning considerably.

If you aren’t bothered by the cleaning aspect at all, and you are happy cleaning fine radiator fins on a regular basis, move the radiator outside of the case and you will get the best cooling situation for both the CPU and inside your case. It will be the supreme choice in all aspects when it comes to cooling.

I recommend a front-mounted radiator configuration. The air from outside the case is cooler, which will allow better cooling through the radiator fins straight off the bat.

Of course, I’m not talking about situations where the radiator is too small and cannot cope with the amount of heat being passed through it. That is just bad practice and doesn’t come into play here.

The overall internal temperature may be raised slightly depending on the configuration of your custom cooling loop, but shouldn’t make any significant difference to the rest of your hardware that could end up causing issues.

Conclusion

As you can see, PC airflow optimization is something that requires some observation and planning. Beyond that, it’s simply common sense thinking about how air moves as a result of your fan configuration and case layout.

Always choose quality components when it comes to your cooling and power. It’s the foundation to build a reliable and long lasting computer.

There is always plenty of debate about which way is better for each component and build. Sometimes it’s not always about achieving the absolute coolest temperature for every single component.

I have found that these airflow optimization techniques are effective enough for cooling while keeping things practical and maintainable.

If you are ever in doubt which way works better for you with something, try it another way. This is the way you learn and become more experienced in setting up machines that don’t overheat and also practical for everyone to use and maintain.

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