Hot Aisle Containment

Hot aisle containment is an airflow design that encloses the rear, hot-exhaust side of server rows so it cannot mix with the cold supply air. Doors and ceiling panels seal the aisle, and cooling units pull the captured hot air straight back. Preventing mixing lets operators raise supply temperature toward the upper ASHRAE recommended limit of 27 degrees Celsius, cut fan energy and often lower PUE by 0.1 or more compared with an uncontained hall. Containment is standard in modern colocation, but air cooling still tops out at roughly 15 to 25 kW per rack, so GPU halls above that level move to rear-door or direct-to-chip liquid cooling. Retrofitting containment into an existing hall is one of the cheapest efficiency upgrades available.