Servers generate an incredible amount of heat, which is unfortunate because extended exposure to heat is one of the quickest ways to ruin valuable IT equipment. ASHRAE recommends keeping server rooms between 64.4 and 80.6 degrees F. Although ventilation and air-recycling systems offer many ways to achieve this temperature range, one of the most efficient and cost-effective methods is aisle containment.

How aisle containment works

Aisle containment is a physical means of separating hot (exhaust) and cold (supply) air. It can be accomplished via thoughtful room design, cabinet layout, aisle level (doors and panels), and cabinet level (blanking panels and rack gap fillers). These techniques help separate the hot aisle from the cold, keeping each isolated.

Laying out servers in a particular pattern causes the hot exhaust from one fan to blow into the intake of the next. This physical barrier prevents “recirculation” of exhaust air from the servers’ air back to the intakes of the computer equipment.

Aisle containment aids in energy-saving initiatives by allowing the operator to raise the supply temperature or slow down fans without fear of creating “hot spots” in the environment. The beauty of aisle containment is its efficiency. It’s not a long-term plan or a piece of equipment. Simply arranging your servers strategically leads to lower maintenance costs and extended equipment life.

Aisle containment types

The two types of aisle containment are hot aisle containment (HAC) and cold aisle containment (CAC). Cold aisle containment systems separate the cold aisle from the hot by capturing the cold air and feeding it directly into the intakes of equipment. Materials such as doors, overhead panels, and lids are typically used to contain the cold aisle. A raised floor is technically part of what should be considered the cold aisle. These types of systems are popular in older data centers. They are easy to set up in existing spaces, and their energy efficiency makes them an excellent option.

Hot aisle containment systems isolate the hot aisle using a similar enclosure system to that of a cold aisle with a sealed door for access. This arrangement is preferred in newer systems and larger, purpose-built centers because it works well with other types of cooling systems, like computer room air handlers (CRAH) and humidification systems. Exhaust air can be easily transported into the CRAH, allowing it to remove the heat and cycle the air back into the server room.

Choosing the right system

While it may be tempting simply to request the “top of the line,” choosing a cooling system is about working with your space. One of the first questions you should ask is, how much control do I have over the space? Some data centers are huge, specialized, and personally built. These types of spaces need constant maintenance from on-site staff, so they do well with hot aisle containment systems. By isolating the hot aisle, IT staff can more easily set up workstations or walk the aisles, maintaining more of a “creature-comfortable” environment.

But not all data centers are the same. Some are small colocation facilities shared by several businesses. These types of spaces would benefit from a cold aisle containment system. With the cold aisle contained, it will be less comfortable to work in the area, but the system will be predictable and energy efficient.

Another question you should ask is, what is my budget? IT energy will be one of your biggest expenses. Managing the heat will be the second biggest. A cold aisle containment system is a budget-friendly option. Containing cold aisles is easy to do with an older space, whereas hot aisle containment systems often require more expensive equipment and renovations. In the long term, hot aisle containment systems generally are more economical, as they are more energy efficient and easier to maintain, resulting in fewer overhead costs.

Deciding on a cooling system is a critical decision — it will greatly affect the life of your equipment. The wrong call can mean a short-lived business and significant loss. It’s important to be well-informed and understand the available options to preserve your infrastructure, data, and business.

Considering an aisle containment system for your data center? Contact the experts at USNet for the perfect plan. Visit to get started.