Hot Aisle / Cold Aisle Containment

Hot aisle / cold aisle is a physical arrangement of server racks in alternating rows where server fronts face each other (cold aisle, receiving cool supply air) and server rears face each other (hot aisle, exhausting warm air). This segregation prevents hot and cold airstreams mixing, improving CRAC/CRAH effectiveness and enabling higher supply temperatures. Containment systems — curtains, doors, or ceiling panels — physically seal the aisle to capture or direct airflows, improving PUE by 20–40 %.