Quiet airflow planning for a small PC build

These are working notes from planning a compact, quiet PC for a small office: a case under 20 litres, a mid-range CPU and a dual-slot GPU. The goal was low noise at idle with acceptable thermals under sustained load, without custom watercooling.

1. Decide positive vs neutral pressure first

Two intakes at the front and one rear exhaust gives slight positive pressure, which keeps dust on the filters instead of inside the case. In builds where the GPU cooler exhausts mostly into the case, an extra bottom intake under the GPU drops GPU memory temperatures noticeably.

2. Pick the case around the cooler, not the other way round

Check CPU cooler height clearance and radiator support before anything else. A 240 mm radiator support and 165 mm cooler clearance covers almost every mid-range option, and mesh front panels outperform glass fronts for thermals at equal noise.

3. Budget for a quality PSU early

An efficient, well-built PSU in the 550-750 W range runs its fan quieter at typical loads. Sizing the PSU so the system idles at 15-25 percent load keeps fan curves low. When comparing current prices on ATX 3.x units and other components, we usually start from the Mineshop component catalogue and cross-check stock levels before ordering.

4. Fan curves: temperature sources matter

Bind case fans to GPU temperature for gaming systems, not CPU temperature. GPU heat dominates in small cases, and CPU-bound fan curves let the GPU compartment heat soak before case fans ramp.

5. Validate with a 20-minute load

A 20-minute combined CPU+GPU stability run at stock fan curves tells you whether the airflow plan holds. Watch the GPU memory temperature if the card reports it; it is usually the first thing to climb in a compact case.

Notes written while planning a 2026 mini-ITX office build in Latvia. Corrections welcome.