New EnergyStar Option for Defining Airflow

In Release 13, we introduced two options for defining airflow through servers based on data from ASHRAE and EnergyStar. We incorporated this wide range of flow rate data into the IT equipment objects in our 6SigmaDCX suite to enable our users to model IT equipment more accurately and ensure better simulation results.

ASHRAE Airflow Data

In 2016, ASHRAE released a series of data depicting the airflow per unit power for a server using historic data to plot a graph. They also included some predicted values for the continued change in values for this airflow over time up to 2020.

The graph below, using a sample of the ASHRAE data, demonstrates that the required airflow per unit power is decreasing slowly over time (ASHRAE, 2016). This indicates that servers are becoming more efficient, which will allow data center operators to make significant energy savings in the future.

Figure 1. ASHRAE sample data graph demonstrates that the required airflow data per unit power is decreasing slowly over time

EnergyStar Airflow Data

EnergyStar describes itself as a “U.S. Environmental Protection Agency voluntary program that helps businesses and individuals save money and protect our climate through superior energy efficiency” (Energy Star, 2018). As part of this operation, EnergyStar produces a template data sheet for manufacturers of enterprise servers to populate so that they can receive EnergyStar ratings for their IT equipment.

Part of this data sheet provides specific thermal information in terms of airflow (CFM) and total power dissipation (W) for minimum, typical and maximum server configurations.

Figure 2. Example of the relevant thermal information from EnergyStar data sheet

At Future Facilities, we have compiled the airflow data from over 100 of these data sheets from a variety of manufacturers and used them to calculate an average Flow Rate Per Unit Power curve.

We have used specific data for the servers that have EnergyStar data sheets available. For servers that lack an EnergyStar data sheet, we have used the average from the compiled data.

Figure 3. Averages from the compiled EnergyStar data sheets

Power Ratio Options

The EnergyStar power ratio has been added as the default value, so the Flow Rate Per Unit Power will automatically be calculated based on the Name Plate Power specified in the IT Equipment property sheet.

EnergyStar data comes directly from the manufacturer, providing a very reliable source for information regarding airflow through their servers. We can also accurately estimate the airflow through any server without EnergyStar data sheets as a result of EnergyStar’s large and growing database of manufacturers.

In turn, the ASHRAE 2016 data contains predicted values and can still be selected in the Cooling node of the IT equipment property sheet.

Figure 4. New options can be found in the Cooling node of the IT equipment property sheet


We have incorporated flow rate data from EnergyStar to determine the default power ratio when defining airflow. Users can still use ASHRAE 2016 values if they wish to do so. We believe that incorporating this wide range of flow rate data will ensure accurate, high quality simulation results. In the future, we hope to continue incorporating the most recent iteration of this data, allowing users to always model with up-to-date airflow data.

Blog written by: Tom Newson, Consultant Engineer

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