The Benefits of Hot and Cold Aisle Containment


All data centers have to grapple with energy consumption and look for ways to minimize high energy costs. Both cold aisle containment solutions and hot aisle containment solutions are strategies that work towards increased energy efficiency. When IT equipment fails, 65% of the time inadequate or badly maintained air conditioning in the server room makes a direct contribution to the problem

The Benefits of Data Center Aisle Containment

When either cold aisle containment solutions or hot aisle containment options are implemented (assuming rack layouts where fronts of one row face the fronts of the adjacent row so that alternating cold and hot aisles are formed), there are benefits to efficiency levels.

  1. There are no more hot spots. The containment lets cooling units get air, unmixed with hot air, to the front of the equipment. This creates uniform IT inlet temperatures and supply air temperatures can be increased without risking hot spots.
  2. Costs for dehumidifying or humidifying go down. Because there is no mixing of hot and cold air, the cooling system air supply temperatures can be decreased so that it operates above the dewpoint. This means no humidity is removed and added humidity is not required.
  3. Cooling systems can be set higher while still keeping everything within safe operational ranges. Another benefit of cold aisle containment solutions or hot aisle containment is that higher return temperatures to the cooling unit result in better heat exchange, which in turn means better capacity for cooling and higher efficiency. All cooling systems generally are able to give higher capacity when return air is warmer.
  4. Physical infrastructure can be sized correctly and run with better efficiency. One of the problems with traditional layouts is that oversizing is required because of the need for extra fan power to overcome obstructions and pressurize the plenum. Implementing cold aisle containment solutions allow for right-sized equipment, which experiences lower rates of fixed loss.
  5. Increased economizer hours are possible. Containment, either hot aisle or cold aisle, allows for increased set point temperatures on the cooling systems. When the outdoor temperatures are colder than indoor, taking into account insulation issues and inefficiencies in heat exchangers, cooling systems are not forced to work to push heat outdoors. Higher set points mean more downtime for compressors and thus more energy savings.

What Are Cold Aisle Containment Solutions?

Cold aisle containment solutions enclose the whole cold aisle so that the rest of the center becomes a hot-air return plenum, separating the streams of cold and hot air. This can be done with ceiling panels and end doors, plastic curtains, and raised floors with perforated tiles. Other arrangments and material solutions are possible.

What Are Hot Aisle Containment Options?

This solution contains the hot aisle and collects the hot exhaust air, making the rest of the center a cold-air return plenum and separating the streams of cold and hot air. This can be done by creating an independent zone or by ducting to a computer room air handler or remote air conditioning unit, among other designs.


Whatever type of data center aisle containment is used, people still need to work within the data center. This means the work environment must be kept at temperatures that OSHA and ISO 7243 guidelines accept for permanent working areas. Hot aisle solutions can result in temperatures becoming too high for personnel permanently stationed at desks in the data center. This can be mitigated by temporary openings of the aisle, or by keeping workers from being permanently stationed there and keeping most routine work done in front of the IT racks. With cold aisle containment solutions, the air in the rest of the room becomes hotter, and those entering the data center will experience temperatures they previously associated with an imminent breakdown. This requires education and a cultural shift for data center operators. Finally, special provision has to be made for any non-racked IT equipment under either a cold or hot aisle containment scenario.

Containment solutions offer a realistic way of lowering costs and increasing energy efficiency for data centers, when properly installed.