Noctua NA-FD1 hands on and testing : a modular fan duct for NH-L9 coolers

Recently Noctua unveiled a new fan duct for small form factor cases that can be applied on NH-L9i and NH-L9a low profile coolers. After the announcement, we can finally test the product in hands to see if it lives up to the expectations.

A quick explanation of how it works

One of the issue in cases with poor ventilation is the recycling of hot air. The fan pulls air from outside the case and blows it on the heatsink’s fins. The air will then warm up and must exit the case since it is not wanted anymore.

In some PC cases, the exhaust doesn’t always work as intended and the hot air stays inside the case. If the fan doesn’t have access to a fresh source of air, it can reuse that hot air and push it onto the fins again, except this time it is already hot, so the fins cannot transfer as much heat as they would. This usually happen if the fan is too far from a vented side panel.

This is where fan ducts come in play. They act as a “tunnel” between the fan and a side panel or a vent, making sure the hot air inside the case does not mix with the fresh air coming from the outside. The effect of a fan duct can vary depending the case and configuration.

The NA-FD1

Noctua has taken an interesting approach to fan ducts with this product. Instead of being a single piece of plastic, the product is made of multiple pieces of foam with different height. This allows you to adjust the height of the fan duct as close as possible to the side panel, and can be reused in multiple cases with different cooler clearances.

Noctua claims the fan duct can decrease cpu temperature under load up to 5°C, which can make a significant impact for cpu performance.

The NA-FD1 also comes with a 6 years warranty.

A small note as i was browsing the performance expectation page, Noctua claims to have tested the 5600x in a Louqe Ghost S1 with an Asus X570-E which is ATX. However, the Ghost S1 can only fit mini-ITX motherboards. This is likely a mistake from Noctua as Asus does have an ITX board which is the Asus X570-i.

The packaging

The NA-FD1 comes in a relatively small package, barely bigger than the cooler it is supposed to mount on. Inside we can find 4 mounting thumb screws, 16 plastic tubes to mount the foam, 7 foam spacers of different sizes, and an installation manual. The tubes and screws are packed in one reusable plastic bag. The packaging is relatively simple and efficient, granted it doesn’t need much protection.

The installation

The cooler can only mount on Noctua’s NH-L9i or NH-L9a. To install the cooler, you need to replace the screws of the fan with the one included in the package.

The plastic tubes need to be cut to the correct length in order to fit under the side panel. There are multiple ways to do this : the manual recommands to measure the height with a toothpick, then mark the cut line with a pencil. If you use this method, do not that you will need to cut a few mm under the mark to take in account the side panel height.

If you know the maximum cooler clearance of the case (often disclosed in the specifications), you can calculate the difference to cut directly on the tube. Both the NH-L9i and NH-L9a are 37mm tall. It is recommanded to cut the tubes one or two mm under the line to avoid any issues with fitting the tube under the side panel.

I used this second method and had no issues with tube length.

According to the manual, the plastic tubes then fit on the top of the screws so you can then fit the foam spacers on top. Then the foam spacers simply fit on it until the maximum height is reached. The thicker spacers should be put first.

With the sample i have, the tubes are bigger than the holes in the foam. It was easier for me to fit the foam on the tubes first, then to fit the whole assembly on the screws on the cooler. This caused no issues with the product however.

The testing

Now to see if we can really reach a 5°C difference with the NA-FD1. The cases i am using to test are the Sliger SM550 and the Xtia Xproto. The SM550 has a 53mm cooler clearance, which means there is a 16mm gap between the side panel and the cooler. The Xproto is an open air case, which will allow us to have a reference benchmark without any case restriction. We can also test multiple heights all the way up to the maximum 45mm height of the fan duct.

Here is the full test system :

CPUAMD Ryzen 3700x
CoolerNoctua NH-L9a
MotherboardGigabyte B550i Aorus Pro
RamCrucial Ballistix 2x8GB 3600cl16
StorageWestern Digital SN750 500GB
Graphic cardSapphire Pulse 5700XT
Power SupplyCorsair SF450
Case(s)Sliger SM550/Xtia Xproto

Everything is running at stock except the ram which is running at XMP.

For testing, i am running cinebench r20 and r23 3 times each and i take the average of the 3 runs. This is done at every height tested. Each cinebench runs for at least 5 minutes and completes the last pass when the timer runs out.

Sliger SM550Xtia Xproto
10mm + 7mm
(maximum height limit)
10mm +10mm
10mm +10mm +7mm +6mm
45mm (all spacers used)
NA-FD1 in the Sliger SM550
NA-FD1 on the Xtia Xproto

After the testing, here are all the results :

SM550 testing
Xproto testing

The results are somewhat in line with Noctua’s advertising. We have an improvement of 3-5°C with the fan duct completely filling the gap in both cases. However, it is interesting to see the different behaviors when using different heights.

I did not expect a 10mm spacer alone to make thermals worse than stock in the Sliger SM550, only for the full 17mm fan duct to create a massive difference in the end.

I was not expecting the fan duct to make any difference on the Xproto either considering it is an open air case, but I am happy it does. Each height adds a tiny improvement to thermals all the way up to 45mm.


The NA-FD1 definitely helps to take off the edge in CPU thermals under load. However, it will not replace a bigger cooler with more surface area or a faster fan. This fan duct is sadly not a miracle worker. Don’t expect it to magically make your overclocked 12900K drop in thermals under 70°C…


  • Modular
  • Noticeable thermal improvements even in open air cases
  • Easy to mount
  • Quality EVA Foam
  • Noctua includes 16 mounting tubes to reuse the fan duct
  • Low price
  • 6 years warranty


  • Only compatible with Noctua NH-L9i and NH-L9a
  • Is not as good as a bigger cooler or fan
  • Screws cannot be screwed with a screwdriver, only thumb

With that in mind it is a nice and inexpensive way to help a 65w TDP CPU stay at reasonable temperatures. It is very flexible and will adapt to a lot of different small form factor cases and doesn’t need to remove the entire heatsink to mount.

The Noctua NA-FD1 can be found on Amazon for 12.90€. At the time of writing, it is out of stock in the US and the price is unknown.

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