Hot/cold aisle containment

Hot/cold aisle containment is a data center layout practice that physically separates cold supply air from hot exhaust air to prevent mixing and recirculation. Racks are arranged in alternating rows facing each other: cold aisles deliver chilled air to equipment intakes, and hot aisles collect exhaust. Containment adds doors, roofs, or curtains around one aisle type — cold-aisle containment encloses the supply side, hot-aisle containment ducts exhaust back to air handlers. Eliminating air mixing lets operators raise supply temperatures toward the ASHRAE-recommended upper range (up to 27°C) and reduce fan speeds, typically cutting cooling energy 20-40% and improving PUE by 0.1-0.3. Containment is standard in modern builds and one of the cheapest efficiency retrofits for legacy air-cooled facilities.