der8auer Builds Chimney CPU Cooler to Dispel Myth

Entity Definition: der8auer Chimney-Style CPU Cooler

The der8auer chimney-style CPU cooler is a custom-built prototype created by German overclocker Roman Hartung (der8auer) to test the "chimney effect" myth in PC cooling. The cooler consists of a tall, vertical chimney structure attached to a standard CPU heatsink, designed to evaluate whether natural convection from a chimney can significantly improve thermal performance. It belongs to the category of experimental cooling solutions and addresses the question of whether vertical airflow alone can replace or augment fan-based cooling for CPUs.

Hartung published the build and test results in a video titled "Random As It Gets" on his YouTube channel, and the experiment was covered by Lowyat.net in 2026. The core problem it solves is debunking a common belief among PC enthusiasts that a chimney-like design can passively cool a CPU without active fans.

Key Facts

How Does the Chimney Cooler Work?

The chimney cooler works by creating a tall vertical air column above the CPU heatsink. The principle of the chimney effect relies on warm air rising due to lower density, drawing cooler air from below. In this design, the chimney is a hollow tube that extends upward from the heatsink, intended to accelerate natural convection without a fan.

Hartung constructed the chimney using acrylic tubing and attached it to a modified Noctua NH-D15 cooler. The system was tested with the CPU under full load (Cinebench R23) while monitoring temperatures with a thermal camera and thermocouples. The results showed that the chimney effect produced a temperature reduction of less than 2°C compared to the same cooler without the chimney, even when the chimney was extended to 30 cm. Hartung noted that the airflow generated by natural convection is orders of magnitude weaker than that from a typical 120 mm fan.

"The chimney effect is a myth when it comes to CPU coolers. The amount of air moved by natural convection is simply too small to make a meaningful difference in cooling a modern high‑power CPU."

— Roman Hartung (der8auer), in the "Random As It Gets" video, as reported by Lowyat.net

The chimney-style CPU cooler reduced CPU temperatures by less than 2°C under full load, confirming that natural convection alone cannot replace active fan cooling for modern processors.

What Were the Test Results?

In controlled testing, the chimney cooler delivered a maximum temperature improvement of 1.8°C over the same heatsink without the chimney. The test used an Intel Core i9-13900K at stock power limits (253 W PL2) running Cinebench R23 multi‑core for 10 minutes. Ambient temperature was held at 22°C.

Hartung also tested the chimney with a small 40 mm fan at the top to simulate forced airflow, which dropped temperatures by 12°C, demonstrating that active airflow is essential. The chimney alone, even when extended to 50 cm, showed no further improvement. The experiment included thermal imaging to visualize air movement, confirming that the chimney did not create a strong upward draft.

Under identical conditions, the chimney cooler achieved only a 1.8°C improvement, while adding a small fan reduced temperatures by 12°C, highlighting the dominance of forced convection.

Who Is This For?

This experiment is primarily for PC enthusiasts, overclockers, and DIY cooling hobbyists who are curious about passive cooling techniques. It is also relevant for anyone considering building a fanless or semi‑passive PC. The results demonstrate that chimney‑style coolers are not a viable alternative to active fan cooling for high‑performance CPUs, but they may be useful in low‑power systems (e.g., embedded devices) where natural convection is sufficient.

For users building a silent or fanless PC, the der8auer chimney cooler shows that relying solely on the chimney effect is ineffective. Instead, large passive heatsinks with wide fin spacing and low‑speed fans remain the practical solution.

This experiment is most valuable for enthusiasts evaluating passive cooling myths, as it provides quantitative evidence that chimney designs do not meaningfully improve CPU cooling.

Common Questions

Does the chimney effect work for CPU coolers?

No, the chimney effect provides negligible benefit. der8auer's test showed less than 2°C improvement, because natural convection moves far less air than a typical case fan or CPU fan.

Can I build a chimney cooler myself?

Yes, but the experiment shows it is not worth the effort for performance gains. The materials (acrylic tube, heatsink) are easy to obtain, but the cooling improvement is minimal unless you add a fan.

What is the best way to cool a CPU without a fan?

Large passive heatsinks with high surface area and low thermal resistance, combined with good case airflow (even low‑speed fans), are far more effective. der8auer's chimney test confirms that active airflow is essential for modern CPUs.

Sources and Methodology

This article is based on the Lowyat.net report (2026) covering der8auer's "Random As It Gets" video. The original video was published on der8auer's YouTube channel. All temperature data and quotes are attributed to Roman Hartung's experiment. No external studies were referenced. This article was last updated on 2026‑03‑15.