Lost Password
Data Center
Success Story

How Containment and Environmental Monitoring Garnishes a Large Utility Rebate

Virtustream is a cloud innovator offering enterpriseclass cloud solutions for enterprises, governments and service providers.

Subzero Containment leads to energy savings and a $49,777.72 utility rebate


Virtustream, Inc. is a cloud innovator offering enterprise-class cloud solutions for enterprises, governments, and service providers. Virtustream simplifies moving complex IT to the cloud – whether private, public or hybrid – delivering the full economic and business benefits of the cloud and virtualization.

Virtustream relies heavily on the consistent and reliable operations of their data centers.

In the spring of 2013 Virtustream researched ways to decrease their operational cooling costs. Additionally, Virtustream was determined to benefit from the generous utility rebates provided by Pacific Gas and Electric Company – PG&E.

From a cooling perspective, they chose containment technology that separates the supply and return airflow since it was a tried and proven system that delivers huge cooling energy reduction.

Virtustream employed Subzero Engineering to manage the project due to their experience in four key areas:

1) Containment technology
2) Utility rebate programs
3) DCEP certified engineers
4) PolarXpress wireless environmental monitoring system.


Increase cooling reliability while increasing the IT performance and getting the local utility company to share in the costs.

Step One – Working with the Utility Company

The first step was to meet with the utility company to outline the rebate requirements. Representatives from PG&E, Virtustream, and Subzero Engineering met at the data center to walk through the program. Subzero supplied two Department of Energy (DOE) Data Center Efficiency Practitioner (DCEP) certified engineers familiar with airflow audits and wireless environmental monitoring.

Step Two – Gather Existing Environmental Data

The second step was to install the PolarXpress wireless environmental monitoring system so that we could fully understand the current airflow patterns, temperature, and relative humidity of the intake at the IT equipment. Measurements were taken all across the face of the racks, as well as the return airflow back to the CRAC units. Thousands of data points were collected. The data revealed that the supply temperature was at its lowest setting but by the time the cooling air reached the middle of the rack the temperature had increased by over 6 degrees. Worse yet, temperatures at the highest U were off by over 10 degrees! Clearly the mixture of supply and return airflow required the cooling units to work overtime just to keep up with the thermal demand.

Step Three – Install the Containment System

Step three was to eliminate the mixing of supply and return airflow. Subzero Engineering installed aisle end doors and a roof system onto the cold aisle. Gaps were filled inside racks to prevent hot air from migrating into the cold aisle.

Step Four – Post Environmental Monitoring

The next step was to measure the results of the containment’s separation of hot and cold airflow. The data revealed that the supply temperature had dropped 11 degrees! Additionally, the temperature differential between the bottom of the rack and the top was only 1 degree.

Step Five – Harvesting the Energy Savings

Step five was to slowly increase the CRAC temperature set points to match the IT equipment supply air temperature. Instead of a loss in supply temperature, the CRAC set points were within a degree or two of the actual required intake temperature. This severely reduced the amount of refrigeration of air required to maintain thermal cooling of the IT equipment.

Final Step – Receiving the PG&E Rebate

The before and after data was then presented to PG&E for their internal auditing. As a result of the energy reductions that were proven to be sustainable by the PolarXpress environmental monitors, PG&E was able to award Virtustream a substantial energy rebate.


  • Containment of supply and return airflow
  • DCEP trained engineers work with PG&E to gather required data
  • PolarXpress wireless environmental monitoring system to gather pre and post readings


10 degree drop in supply airflow, which was converted into energy savings, with a 8 degree increase in temperature set points. Virtustream was awarded $49,777.72 utility rebate.


Containment of the supply and return airflow now provides the Virtustream data center with a consistent, reliable temperature at the IT intake. At the same time, it reduces the cost of cooling by reducing the temperature set points. Finally, the environmental monitoring system (PolarXpress) provided real-time data to support a large energy rebate from the local utility company. Virtustream is meeting the challenge of increasing the IT performance, while at the same time reducing its operational costs.