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Keeping Your Computer Cool: Part One - The Case

There are many benefits of a cooler computer such as increasing its lifespan and allowing for higher overclocks, but how can you reduce your systems temperature?


Over the weekend I discovered that my in-house server was running VERY hot, it?s a headless server (i.e. it doesn?t have a monitor, keyboard and mouse) which I don?t often tend to pay much mind to. It sits in the cellar head and serves my other devices around the home with various media and services. So I generally only check on it once a month or if something goes wrong.

Saturday morning however I got up to head out on the motorcycle for a few hours and noticed that the cellar head was incredibly warm compared to the rest of the house which prompted me into thinking that maybe it was time to look at the cooling on it and which is obviously what inspired this article.

In part one of this series I?m going to cover the case itself which will provide your system with most of its air flow and if you have a poorly optimised cooling setup in your case, upgrading things like the CPU heatsink and fan can sometimes be in vain. For that reason I?m going to cover optimising the case first and components later.


Before you can tackle the overall goal of improving your systems cooling, you have to understand your computers case and how it was designed to handle airflow. Most standard mid tower cases are designed to draw air in through the front and bottom and expel it out of the back and top. Given that heat rises it?s always almost standard to have some ventilation near the top of the case on the rear.

Power supply units mounted at the top of a PC case also acts like an exhaust for heat generated by other components inside the system; this is good and bad in different situations. If for example the ambient temperature in your case is high, the PSU?s air supply is already warm. This could mean that the PSU is in fact getting ?pre-heated? by the other components inside the case.

On the other hand however if you don?t have any case fans installed in your system the PSU can be the primary cause of ambient airflow in your case. But that?s not something that you just want to leave down to the PSU unless your system is designed for that, but I digress.

As I mentioned above, air flow in most case designs is as depicted in the diagram below:

In the diagram above (which I?m quite proud of) we can see that cold air is being drawn in at the front and bottom of the case. The part at the rear is where we would have a power supply mounted fan down, this means the power supply is just concentrating on cooling itself.

The air at the front of the case is drawn inwards by the fan and then upwards due to two factors: Firstly the heat from your hard drives causes it to heat up ? thus naturally rising and secondly the airflow is being drawn upwards by the top and rear fans.

Now that we understand the typical airflow scenario with most desktop tower cases we?re ready to look at our own and identify where and how we can improve it.

Installing Additional Case Fans

Your case may support the installation of additional fans, the best way to identify if this option is available to you is to physically inspect the chassis for any fan grills and mounting points that aren?t in use.

Because fans are available in different dimensions the sizes of the grills may vary from case to case. The most common sizes we see in desktop tower cases are 80mm, 120mm and 140mm.

As an example I?ve highlighted multiple places that the case below has available to mount additional fans.

Although it?s not glaringly obvious from this angle the case above supports 2 x 120mm fans on the top, 1 x 120mm fan on the bottom and 1 x 120mm fan on the rear next to your motherboards I/O shield.

So based on our diagram earlier which showed us how the heat would travel through a typical computer case, if you were to fit a 120mm fan to every available grill what direction would you have each fan blowing? Obviously we?d have the bottom fan drawing air in, and the tops exhausting it.

Now there?s a rule to tell which direction air will be passing through a fan without having to plug it in or fit it and find out you?ve got it going the wrong way etc. the rule I?ve always used and which has never failed me is that the side of the fan which the motor is secured to, is the exhaust side of the fan. So for example:

In the picture above, if you were to look at a fan head-on air will be traveling from the part that we?re looking at (the front) out through the rear. So to re-cap the fixed side of the fan is always the side that air comes out of.

Some cases may have fan mounting options behind the front panel, which is usually removable on most cases. So it?s always worth checking (as pictured below) to see if your case has one or will support one.

Some systems may not have the expandability options such as the cases used in the examples above, some may also come fully populated with fans. If this is the case (pun) you can still upgrade the pre-installed fans for aftermarket ones which will improve the overall cooling performance of the case.

If you?re happy with the cooling performance of your case we?re going to cover other aspects of cooling components such as CPU coolers in part two of this series.