PC Airflow Optimization (Fan Configuration Guide)

Understanding how cooling works inside a computer case is vital for the best PC airflow optimization.

I’ll mention that it’s easy enough to create decent airflow inside a computer case and get the system temperature down to acceptable levels, but the true challenge is keeping it cool, quiet, and clean as time passes.

The main three types of case air pressure

We will start by looking 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: It has its blowing side mounted to the wall of the case. It draws air from the inside and blows it outside.
  • Intake fan: It Draws air from outside the case and blows it inside.

Negative air pressure

Negative air pressure configuration example. A diagram shows a computer case with one fan blowing air in and three fans blowing air out.

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

Examples include:

  • More exhaust fans of the same size or larger than the intake ones.
  • The exhaust fans spin faster and are the same size or larger than the intakes.
  • The exhaust fans have a higher airflow rate specification than the intake ones.

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 often result in more dust being pulled into your system 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 there 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 unfiltered intake areas.

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

Positive internal air pressure

A positive air pressure configuration example. A diagram of two fans blowing air into the case relying on the case vents for air to escape.

Positive air pressure means more air is blown into the case than out. The intake fans have a higher airflow rate than the exhaust ones.

While having some positive internal case air pressure is good, it is not the best if it’s too excessive.

If a lot of air is being forced into the case with little exhaust airflow, you can find yourself in a position where insufficient air movement occurs.

This results in stagnant air, which can get hot from the internal components and raise the PC’s internal temperature.

Slightly positive air pressure (More balanced)

A diagram that shows an example of a positive air configuration but with good case airflow. It shows two fans blowing air into a case and one fan blowing air out.

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 (but not equal air pressure), plenty of air is still exhausted, which means plenty is flowing in and out to help achieve optimal airflow.

This leaves little chance for stagnant air hanging around to warm up and prevents the internal temperature from rising above desired levels.

How to configure the fans

Take a look at the fans that you currently have on your PC. Take note of how many intakes you have versus the number of exhaust fans.

If you have any noisy fans, disconnect them one at a time until the noise is gone.

You will then be clear on which fans you need to replace. If one or more are noisy from a cold start-up but go quieter as they spin, 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.

Fan airflow direction

The directional arrows illustrating the airflow and blade rotation directions.

Fan airflow direction is determined by the direction that it is facing. Take note of the small arrows stamped on its casing to see the rotation and airflow directions.

Some say that the intake side is always the top of the blade side, but I find this too generalized and not specific enough compared with the arrow markings on the fan itself.

Assess the number of fans you need

The computer case size will dictate how many you can install to a certain degree.

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

If you have a larger full tower case, three intake fans at the front and one rear exhaust would be a good starting point for optimized airflow.

A larger case has more areas where air can be pushed out than a smaller mid-tower. So, I recommend a minimum of three intake fans to optimize airflow.

Try to stick to the largest your case can support. You will be very happy you have done this later to enjoy a quiet system.

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 a ball bearing instead of a sleeve bearing. It will last much longer.

In some situations, adding an extra fan at the upper rear of the case can help keep the CPU cooler. Not all cases have mounting locations 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 speed control so easy from most controllers even when controlling them from a motherboard.

Configuring the fan control speeds

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

If you plan 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-speed automation when the temperature alters inside the PC case.

This is achieved using temperature sensors to get temperature readings.

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

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

All the fans connect to a module that 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 controllers.

More expensive models have a firmware package that automatically accepts programmable profiles to control the fans concerning temperature readings.

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

How to maintain good airflow while keeping everything quiet

In essence, try to install the largest fans you can.

This might go against someone’s first thought: bigger fan blades equal more noise.

While there is truth to that, there are other factors to consider. Motors drive fans.

Motors spinning at a higher RPM (Revolutions Per Minute) can generate more noise. And the same holds for the blades moving through the air.

When you use a larger fan, a greater airflow rate can be achieved at a lower RPM. This means they 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 keep your system cooler and quiet is the number of fans you use.

A few more large ones spinning slowly is way better than one spinning faster to try and achieve proper cooling.

When it comes to 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 needed, reducing unnecessary higher spinning speeds, which generate more noise.

Rubber-mounted fans also add a little extra help when attempting to keep things quiet. It will lower the amount of vibration produced.

How to test the airflow inside a 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 comes in from the intake fan(s) versus the exhausts.

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 right away. It most likely happened when an extremely cheap fan was installed.

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

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

Checking the air filters

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 quickly make fans, heatsinks, and the inside of your PC case dirty.

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.

Some mesh-style filters are fine, but this will probably mean you need to clean them more often. This is usually fine, as they are designed for easy removal and reinstallation.

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

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

Hardware like cables can cause flow issues. So always ensure the inside of the case is tidy and free-flowing.

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

Recommended graphics card cooling fan configuration

Graphics cards with different style fan configurations. One a blower style, and the other a shroud style.
A blower-style fan on the left and a shroud-style fan on the right.

Regarding air cooling for your graphics card(s), manufacturers use two main styles of cooling. One is a fan blowing on a heatsink with a shroud, and the other is a blower-style fan.

Blower-style fans are just about phased out of the market, so you probably won’t see these coolers on graphics cards anymore.

The graphics card is the component that generates the most heat in a PC by far, so ensure that the card has adequate cooling before considering a purchase.

Please read my article on how to speed up graphics card fans to know more about profiles and temperature curves.

Things to consider for water cooling

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

One typical example of this is an AIO (All-In-One) cooler. It’s usually a closed-loop cooler that’s easier to install and maintain.

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

If you aren’t bothered by the cleaning aspect and are happy to clean fine radiator fins regularly, move the radiator outside the case, and you will get the best cooling situation for both the CPU and inside.

It will be the supreme choice in all aspects of cooling.

I recommend a front-mounted radiator configuration. The air outside the case is cooler, allowing 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 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. Still, it shouldn’t make any significant difference to the rest of your hardware, which could end up causing issues.

How many fans does a gaming PC need?

Although your country’s climate or ambient room temperature plays a major factor in this, a minimum of three fans is recommended. Although five or more is better, having two of them bringing in cool air and one drawing air out is the minimal acceptable configuration.

In most situations, five fans are enough to keep enough cool air flowing in and out of the case.

I recommend considering three intake fans in the front and two exhausts. You can place one exhaust fan at the back of the case and one at the top as far back as possible. Or simply having the two exhaust ones at the back will do just fine.