Data Center Temperature Guidelines and Best Practices


To ensure that a Data Center is functioning properly, it is important that the room temperature is regulated. Excessive heat can put a Data Center at risk of failure. Failures lead to downtime, which leads to lost data and revenue. Based on a Gartner study, it is estimated that the cost of one hour of downtime can amount up to $336,000 per hour or $5,600 per minute. Maintaining the Data Center temperature is crucial in preventing major financial losses.

The ASHRAE TC 9.9 data center temperature guidelines are followed by the industry. However, they are not a legal standard. ASHRAE published the 90.1 “Energy Standard for Buildings – Except for Low Rise Buildings,” which is referred to by state and local building departments. It contains prescriptive methodologies for data center cooling systems. These prescriptions could be in conflict with facilities adopting more advanced IT equipment.

ASHRAE Standard 90.4-2019, Energy Standard for Data Centers indicates the minimum energy-efficiency requirements for the operation and design of data centers. It also takes into consideration their unique needs compared to other buildings. It was developed under the premise that data centers are critical facilities that require meticulous attention.

How are IT industries affected by these guidelines?

Data Centers undergoing new construction or renovations are primarily affected by the new ranges defined in the 2011 ASHRAE guidelines. It contains updated allowable ranges for classes A3 and A4. They are designed to reduce obstacles in new data center cooling strategies such as free-cooling methods. Free-cooling utilizes a facility’s local climate by making use of the outside air to cool IT equipment without using mechanical refrigeration. Adhering to the new ASHRAE guidelines may maximize free-cooling in cool climates. It allows the data center to be cooled without mechanical refrigeration for a longer period. Less use of refrigeration equipment means lower operating expenses. Capital investment is also saved by eliminating or significantly reducing refrigeration equipment.

Despite the change of allowable ranges, the ASHRAE recommended operating range remains unchanged. It is constant throughout all operating classes. If unavoidable, IT equipment should be kept outside the recommended range for a limited time.

Raising a cooling system’s temperature beyond the recommended range may have undesirable consequences:

– Heightened fan operation within the IT equipment. This can disrupt cooling system savings and increase noise levels.

– Warning/ alarm notifications from IT equipment operating beyond recommended levels.

– Reduced lifespan of IT equipment due to prolonged exposure to high temperatures.

Shifting to free-cooling methods requires meticulous facility planning if constructing a new one. Free-cooling under the ASHRAE ranges can lead to significant CAPEX and OPEX savings if executed correctly.

Prescribed Computer Room Temperature

Data centers and server rooms have a combination of hot and cool air. Server fans thrust out hot air while running. Meanwhile, cooling systems bring in cool air to negate the hot air produced by the exhaust. Finding the right balance is essential in avoiding data center downtime.

The range that ASHRAE recommended for optimized maximum uptime and hardware life is between 64° to 81°F (18° to 27°C). This range provides accommodates sufficient buffer in case of air conditioning malfunction.

Server manufacturer Dell states that the ideal temperature for their servers is 80°F (26.7°C). Data centers and server rooms using higher allowable temperatures do not need to cool them as much as they did previously. Less cooling time means reduced power consumption and additional monetary savings.

Higher operating temperatures can lead to less time for reaction in the event of escalating temperatures. A data center with servers operating at higher temperatures carries the risk of simultaneous hardware failures. The ASHRAE regulations emphasize the importance of proactive temperature monitoring inside server rooms.

Prescribed Computer Room Humidity

Relative Humidity (RH) is the ratio of the amount of water vapor present in the air at a particular temperature to the maximum that the air could hold at the indicated temperature. It is expressed as a percentage, and a higher value means a more humid air. In a server room, it is recommended that ambient RH levels are within the range of 45% to 55%.

ASHRAE’s 2016 guidelines maintain the same recommendation, with 50% humidity. The minimum is recommended at 20%, while the maximum is 80%.

Dry air caused by low humidity can lead to an electrostatic discharge (ESD). ESD can destroy essential server components. Too much humidity leads to condensation, which causes corrosion and potential short circuits.

Key topics in data center temperature standards:

Power Usage Effectiveness (PUE)

The initial PUE measurement determins a data center’s energy efficiency. However, it can be misleading because some facilities claim low PUEs during a cold spell when the need for cooling is minimized.

It was updated to PUE version 2, which took into account annualized energy instead of power. It categorized PUE into four, PUE 0-3, and three specific measurement points. If the data center does not have the needed energy meters at the specified measurement points, they use PUEo, which measures power based on the highest draw during warm weather to provide a more accurate representation. The other three PUE categories are based on annualized energy (kWh). AKCP power monitoring equipment can be used, together wit temperature sensors. This allows you to continuously monitor PUE and fine tune the data center operations. Ensuring maximum efficiency while maintaining safe operating temperatures.

Temperature references

Dry Bulb Thermometer

The “Dry Bulb” thermometer (analog or digital) readings are not influenced by the air humidity level. Instead, it measures ambient air temperature. It is the most commonly used type of thermometer. Dry-bulb temperature or “air temperature” is measured with a Dry Bulb thermometer. It is exposed freely to the air but protected from radiation and devoid of moisture.

Wet Bulb Thermometer

The “wet bulb” thermometer is equipped with a bulb covered by a muslin sleeve. This is kept wet with distilled/clean water, exposed to air, and free from radiation. The reading is obtained by a standardized velocity of air flows over the instrument, causing evaporation. The rate of evaporation and the corresponding cooling effect is affected by the air moisture content. It indicates a lower reading in drier air conditions due to the evaporation of the moisture around the bulb.

Dew Point Temperature

The Dew Point is the temperature where the air becomes completely saturated, and the water vapor begins to condense out of the air. Its effect is usually observed when condensation forms on an item that is colder than the dew point. The humidity range in IT equipment operations should always be specified as “non-condensing.” It is an essential consideration for electronic equipment that needs to be kept free from moisture.

Recommended vs. Allowable temperatures

The “recommended” temperature range remains relatively constant at 64.4-80.4°F (18-27°C ) as of 2011. However, the recent “allowable” A1-A4 ranges came as a shock to the industry.

The “allowable” data center classes were established to broaden the options and provide additional information in data center temperature regulations. Still, it introduced a more complicated process for data center operators when balancing reliability, optimized efficiency, reduced ownership costs, and improved overall performance. Allowable temperatures are drafted to accommodate operating ranges of newly introduced, more-thermal resistant equipment.

Neudorfer, J. (2016). Understanding Data Center Temperature Guidelines. Retrieved 25 November 2020, from

Room vs. IT Inlet

In the first edition of the summary of Thermal Guidelines, the temperature of the “room” was initially measured in correlation to ideal data center conditions. However, “room” temperatures are unreliable since different areas across the whitespace can have substantially varying temperatures. In the second edition, an amendment was made in terms of how temperature is measured. The guidelines referenced the temperature of the “air entering IT equipment.” This emphasized the importance of airflow management in higher IT equipment densities and the suggested solution of a Cold-Aisle/ Hot-Aisle cabinet layout. To maximize temperature monitoring capabilities, thermal sensors placed per aisle and per cabinet are highly recommended.

Environmental Specifications

The telecommunications industry crafted environmental specifications prior to the release of the first edition of the ASHRAE TC9.9 Thermal Guidelines in 2004. The NEB’s — or Network Equipment-Building System — environmental specifications lays out physical, electrical, and environmental prerequisites for the exchanges of telephone system carriers. ASHRAE has then expanded its environmental operating parameters to be more aligned with NEBS specifications including the recommended numerical values. The 2011 TC9.9 updated A3 specifications have become parallel to the previously established NEBS allowable temperature range of 41-104°F (5°C- 40°F).

AKCPData Center Temperature Guidelines and Best Practices