Containment enclosures are the various physical barriers used in addition to a hot or cold aisle arrangement. They eliminate the mixing of cold air and hot exhaust air. Containment structures cause a higher allowable temperature in data centers.

The higher temperatures save energy since fan speeds can be lowered, free cooling can be utilised more often and chilled water temperatures can be raised. Containment barriers can have either the cold or hot aisle.

Savings and Costs

Containment systems can reduce the energy used by 5-10% in data centers that have hot or cold aisle containment curtains.

Containments can bring down the fan energy by up to 20-25% and offer energy savings straight from the chiller.

PG&E’s experience with containment shows that the typical paybacks can be less by up to two years.

Other costs that need to be considered are;

  • Associated labour, vendor costs and overtime where applicable.
  • Server room design
  • Any adjustments to the HVAC system.
  • Electrical costs to configure power distribution to the racks again.

data center enclosure towersBNY Mellon and RagingWire are two energy star certified data centers that employ the hot aisle containment during one of their efficiency upgrades. This exercise led to energy savings through the higher chilled water temperatures.

If you would like to read their case studies, visit


Public service announcements recognized these two companies as low carbon IT champions.

Google’s Green DataCenters, a Network POP case study studies the efforts of a small data center on efficiency with optimized air vent tiles, humidity and temperature adjustments, CRAC air return extensions and cold aisle containment that had an ROI of less than a year.

    • When cold aisle is controlled, the rest of the data center gets warm. This may not be ideal for some equipment or staff.
    • Many direct expansion CRAC units cannot be retrofitted with variable speeds which allow the fans to run at different speeds that consequently save energy.
    • Although many CRAC units employ utilise return air temperature to show the room temperature, this does not work in a cold or hot aisle with containment configuration, because, the returned air is usually concentrated and therefore hotter.
    • A paper by American Power Conversion argued that hot aisle containment is better since the hottest air is sent to back the AC, it results to a better cooling unit efficiency.
    • Depending on the location in the data center, adjustments to fire suppression systems or fire detection might be needed.

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