Fans in the floor of your case look like a sure win. Cool air sits low, the graphics card sits right above it, so blowing it straight up should help.
Sometimes it helps a lot. Sometimes it does nothing at all, and once in a while it makes things worse. Seven real tests show which is which.
The short answer
Bottom fans are worth it when three things are true:
- They blow at the graphics card. Fans on top of the power supply shroud, aimed up at the card, help most.
- The floor can breathe. The case sits about an inch above the desk, and the bottom filter isn’t clogged.
- They’re set as intake. Never run bottom fans as exhaust.
If your graphics card is the part that runs hot, add them. If your CPU is the problem, spend the money on side or top fans instead.
What the tests found
| Case | Bottom fans | Result |
|---|---|---|
| Antec Flux Pro | Shroud intake, with vs without | GPU 38°C with them, 43°C in the test without them |
| Lian Li Lancool 217 INF | Added two intake fans | GPU 49°C down to 46°C |
| Hyte Y70 | Bottom vs side intake | GPU 45°C vs 48°C |
| Thermalright A70 | Added intake fans | Little change until the bottom filter came out, then 42°C |
| Cooler Master NR200 | Bottom intake | No change to the GPU |
| Lian Li O11 Dynamic | Three bottom intakes | Poor, worse than side intake |
| Cooler Master Q500L | Bottom intake into the GPU | Among the hottest GPU results |
All temperatures are above room temperature. Sources: Gamers Nexus’ Flux Pro, Y70, A70, O11 Dynamic and Q500L reviews, KitGuru and Hardware Canucks.
One note on the Flux Pro: Gamers Nexus’ test without shroud fans also used different front fans. Even so, it called the result proof that the shroud intake fans were doing something.
When bottom fans help
The wins have something in common: the fans sit on top of the power supply shroud with a clear shot at the card. In the Flux Pro and the Lancool 217, the fans blow straight into the graphics card’s own fans.
They also help most in glass-front cases with no front intake, like the Hyte Y70. There, the floor is one of the only places fresh air can come in. Our dual chamber case guide covers those cases.
When they don’t
The card blocks the air. In the original O11 Dynamic, Gamers Nexus found the flat graphics card blocked most of the air going up, so it just circled under the card.
The case is cramped. In the Q500L, bottom fans pointed at the card showed up in three of the four hottest GPU tests. The card ended up pulling in its own hot exhaust.
The case is tiny. In the small NR200, a bottom intake couldn’t do anything for GPU temperatures. Our Mini-ITX guide explains what works better there.
Never set bottom fans to exhaust
When Hardware Canucks flipped the NR200’s bottom fan to exhaust, the graphics card’s temperature maxed out. A bottom exhaust pulls air away from the card and fights the hot air rising off it.
Not sure which way your fans blow? Use our fan direction checker.
Give the floor room to breathe
Bottom fans can only pull in what reaches them.
- Height off the desk. Gamers Nexus finds about a 1 inch clearance is advisable for anything relying on bottom intake. Short feet, carpet or a desk mat can choke it.
- The bottom filter. In the A70, the filter held back the new fans until it came out. Gamers Nexus also found the Hyte Y60’s bottom filter restrictive enough to hurt GPU temperatures. Keep yours clean.
Slim fans and reverse blade fans
If a thick graphics card leaves little room above the shroud, slim 15 mm fans fit where normal ones don’t. Our Mini-ITX guide compares them.
If your bottom fans show through a glass side panel, reverse blade fans keep the clean side facing out. See our reverse blade fans guide.
Related guides
- Lian Li Lancool 217 setup, which ships with two shroud fans.