Computers need cooling to remove the heat their components generate during use. If you’re building your own PC — especially if you’re overclocking it — you’ll need to think about how you’ll cool it.

Heat build-up can actually damage your computer’s hardware or cause it to become unstable. Modern PCs may shut down and refuse to operate if they reach a potentially unsafe level of heat.

Heat Sinks

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A heat sink is a passive cooling system that cools a component by dissipating heat. For example, your CPU probably has a heat sink on top of it — that’s the large, metal object.

CPUs don’t just have heat sinks — if you have a dedicated graphics card, your GPU probably has a heat sink as well. Other components on your motherboard may have their own heat sinks, too. Heat moves from the heat-generating component to the heat sink pressed against it. The heat sink is designed with a large surface area, exposing a large amount of its surface to the air to dissipate heat more efficiently.

Thermal Compound

CPUs and GPUs generally have a thermal compound between them and the heat sink. This may be called thermal grease, thermal gel, thermal paste, heat sink paste, or many other things. This material is smeared on top of the CPU, and then the heat sink is pressed down on top. The thermal compound fills any air gaps between the heat-producing component and the heat sink allowing more efficient transfer of heat. Be careful when applying this stuff, as you don’t want to use too much — you just want enough to fill in the air gaps between the CPU and heat sink, not so much that it will ooze out the sides and make a mess.

Some heat sinks ship with thermal pads on their undersides. This makes them easier to install, but the pads are less effective at conducting heat than typical paste. An included thermal pad may be good enough for running a CPU at its stock speeds, but isn’t ideal for overclocking.

Thermal compound can deteriorate over time. If your CPU is generating more heat than normal and you’ve dusted out your heat sinks and fans, you may sometimes need to reapply fresh thermal compound.


Fans force air to move, so the hot air is blown away from heat-generating components and expelled from the desktop or laptop PC‘s case. Fans typically blow hot air outward, but you could set up a system of fans to suck cool air inward on the front and blow out air out the back. Fans are an active cooling solution — they require power to run.

A typical desktop PC may contain multiple fans. The CPU itself often has a fan on top — so the CPU is inserted into the socket on the motherboard, thermal paste is applied to the top of the CPU, and the heat sink is attached to the CPU. The fan is placed on top of the heat sink, ensuring the hot air is blown away from the heat sink and CPU. Dedicated NVIDIA and AMD GPUs often have a similar setup, with heat sink compound, a heat sink, and a fan of their own.

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Fans are also integrated into desktop power supplies. On laptops, they’re placed so they can blow hot air out of a strategically placed air vent. On desktops, they may be placed to blow air out of the desktop’s air vents. When building your own PC, you’ll want to think about how air will travel so the PC will stay cool. This isn’t necessary if you’re building a power-efficient PC that generates little heat, but it is a concern if you’re building a gaming PC with a powerful CPU and GPU — especially if you’re be overclocking them.

Dust build-up can clog heat sinks, fans, air vents, and your computer’s case, blocking air flow. This is why it’s a good idea to regularly dust out your computer’s case. You should also ensure your PC’s air vents aren’t blocked or the air will have nowhere to go and the computer will overheat.

Water Cooling

The above methods are the typical types of cooling solutions you’ll find in most PCs, although some power-efficient PCs are designed to work without fans. Still, enthusiasts sometimes opt for more extreme cooling solutions.

Water cooling, or liquid cooling, was originally for mainframes. Enthusiasts who want to overclock their hardware and push it as far as possible like water cooling because it’s more effective at cooling than fans, so a water-cooled PC can be overclocked further.

Water cooling involves a pump that pumps water through tubes that travel throughout your PC’s case. The cool water in the tubes absorb heat as it moves through your case and then leaves your case, where a radiator radiates the heat outward. This is only necessary if you need to deal with an extreme amount of heat — for example, if you’re overclocking more than typical cooling solutions can handle.

You can buy water cooling kits, so this isn’t as hard to set up as you might think, but these kits do cost hundreds of dollars. They also consume more power and are more complex. If a tube springs a leak and starts spraying water inside your running computer, you’d likely have a disaster on your hands.

Immersion Cooling

Immersion cooling is less common, but even more extreme. With immersion cooling, a computer’s components are submerged in a thermally conductive, but not electrically conductive, liquid. In other words, don’t use water for this! An appropriate type of oil will typically be used for this.

The computer’s components generate heat, which is absorbed by the liquid surrounding them. The fluid is more efficient at absorbing heat than air. The surface of the fluid is exposed to the air, and the heat dissipates from the surface of the fluid to the air.

In other words, imagine filling your entire computer’s case with oil and leaving your components submerged to cool it. You’d obviously want the appropriate type of oil and a case that won’t leak!

Some enthusiasts do go this route, but it’s much more rare than water cooling systems. This technique is used to cool some supercomputers.

There are other, more exotic ways to cool a PC, too. For example, you could use “phase change” cooling — this is basically like a refrigerator for your PC. It’s obviously more expensive and draws more power.

When building your own PC, get the usual heat sink, thermal compound, and fans — that will probably be enough. If you want to go crazy with overclocking, get a water cooling solution. You probably shouldn’t go beyond water cooling!

Image Credit: Dave Monk on Flickr, Fir0002/Flagstaffotos under GFDL 1.2, gcg2009 on Flickr, Guilherme Torelly on Flickr, Don Richards on Flickr, Darkoneko

Profile Photo for Chris Hoffman Chris Hoffman
Chris Hoffman is Editor-in-Chief of How-To Geek. He's written about technology for over a decade and was a PCWorld columnist for two years. Chris has written for The New York Times and Reader's Digest, been interviewed as a technology expert on TV stations like Miami's NBC 6, and had his work covered by news outlets like the BBC. Since 2011, Chris has written over 2,000 articles that have been read more than one billion times---and that's just here at How-To Geek.
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