The cheap five
One: blanking panels in every empty U — recirculation is the silent killer. Two: floor-grommet seals around cable cutouts. Three: raised set-points; modern IT hardware is warrantied to 27°C inlet, and most rooms run far colder than their gear needs. Four: hot-aisle containment where the layout allows even a curtain-based version. Five: a quarterly airflow audit with a thermal camera — you will find the bypass every time.
Sequence matters
Do the airflow work before touching the cooling plant. Rooms that fix recirculation first routinely find they can shut down one CRAC unit entirely — which is a capital decision made possible by a maintenance decision. Retrofitting chillers on top of a leaky room just pays to cool the plenum.
