A small case packs a hot graphics card and a hot CPU into a box the size of a shoebox. Get one fan backwards and they start breathing each other’s exhaust.
The good news is that most small cases want the same basic layout. Here it is, then the test data behind it.
The layout to copy
Pull cool air in through the side, and push hot air out the top.
| Fan spot | Set it to | Why |
|---|---|---|
| Side panel | Intake | Feeds fresh air straight to the CPU cooler or graphics card |
| Top | Exhaust | Hot air rises, and the top sits right over the GPU |
| Rear (often 92 mm) | Exhaust | Clears warm air from around the CPU |
| Bottom | Intake, or leave it empty | Tests show little gain, and exhaust here hurts the GPU |
If your case has a mesh side panel, use it. In one test of the Cooler Master NR200P, swapping the mesh side for glass raised CPU temperature by 7°C.
Why small cases run hot
In a big tower, each part has room to breathe. In a small case, the GPU’s hot exhaust often lands right on the CPU cooler, or gets pulled back into the GPU.
Gamers Nexus saw this in the Fractal Terra. The stock layout had the worst GPU temperatures on its chart because warm air kept circling on the GPU side. Giving the GPU fresh air from the side panel cut its temperature by about 4°C.
The fix is to give each part its own path:
- Fresh air in right where the GPU and CPU fans pull from.
- Hot air out above them, before it can loop back.
Should the top fans be intake or exhaust?
Exhaust, in almost every small case. When Hardware Canucks removed the top exhaust fans from the Cooler Master NR200, GPU temperature went up a lot.
A top intake can work in some layouts. We haven’t found a measured test that shows it beating top exhaust, though. To compare both in your own build, try each one in the free Mini-ITX case in the simulator above.
Are bottom fans worth it?
Often not. Here’s what testing found:
- NR200, bottom intake: Hardware Canucks found it couldn’t do anything for GPU temperatures.
- NR200, bottom exhaust: the GPU maxed out. Never set bottom fans to exhaust.
- Fractal Terra, two slim bottom intakes: Gamers Nexus measured about 1.4°C better on the CPU and almost no change on the GPU. They called it “not worth all the noise and hassle.”
So spend money on side and top fans first. Add bottom fans last, and only as intake.
Layouts by case type
Small cases come in three main shapes. Each one wants a slightly different plan.
Shoebox cases (Cooler Master NR200P, Fractal Terra) have the GPU and CPU side by side. Use side intake and top exhaust. The NR200P has room for two 120 mm fans on top, two on the bottom, side fans and a 92 mm rear fan.
Sandwich cases (Lian Li A4-H2O, Fractal Ridge) put the GPU behind the motherboard on a riser cable. The GPU pulls air straight through its own side panel.
In the A4-H2O, putting a two-slot GPU in the outer slot so it could reach fresh air cut GPU temperature by 6.8 to 8°C. The Fractal Ridge has room for two 140 mm side fans plus three 80 mm top fans.
Tower-style ITX cases (Corsair 2000D Airflow) are tall and narrow, with fan mounts on the front, side and rear. The 2000D takes up to eight 120 mm fans. There are no top mounts, so run the side fans as intake and the rear fans as exhaust.
Check which way each fan blows
This is the most common mistake in small builds. On most fans, air leaves through the side with the sticker and the support struts.
Noctua puts it simply: with the sticker facing you, the air blows toward you. So for an intake, the sticker faces into the case. For an exhaust, it faces out.
Many fans also have small arrows on the frame that show airflow and spin direction.
Slim fans for tight spots
Some small cases only fit 15 mm slim fans under a thick graphics card. They work, but they move less air.
| Noctua fan | Thickness | Airflow | Static pressure |
|---|---|---|---|
| NF-A12x15 PWM | 15 mm | 94.2 m³/h | 1.53 mm H₂O |
| NF-A12x25 PWM | 25 mm | 102.1 m³/h | 2.34 mm H₂O |
The slim fan loses about 8% of the airflow and about a third of the pressure. That’s fine on an open bottom mount, but weaker behind a radiator or a dense filter.
Dust filters
Filters keep your parts clean, and a clean filter costs very little. Hardware Canucks measured 2°C on the CPU and 1°C on the GPU with the side filter in the NR200.
A clogged filter costs more, so rinse them every month or two.
Set your fan speeds
Noctua suggests setting fan curves in the BIOS rather than in software. In a small case, keep the top exhaust fans running whenever the GPU is busy, since they carry its heat out.
Our sister site can turn your temperatures into a fan curve for you.
Next steps
- Own an NR200P? See the Cooler Master NR200P setup, with layouts for air coolers and AIOs.