U.S. Green Building Council
Air and Water Balance (Retro-commissioning)

Air and Water Balance

Enterprise is certified by the National Environmental Balancing Bureau (NEBB) to perform and manage all mechanical and ventilation system testing and balancing. The company applies and conforms to all NEBB procedures and standards for air and hydronic environmental systems.

The Enterprise certification number is 2881.

Testing and Balancing (TAB) systems is sometimes equated with commissioning/retro-commissioning. Please download the article "Why Commission Mechanical Systems" and a case history of retro-commissioning (Cleveland Clinic article) to learn more about the importance of this service to you and your business.

Or click here to read other IAQ and TAB case studies and articles.

This article is in Adobe Acrobat Portable Document Format (PDF) and requires that you have the Acrobat Reader installed on your computer.

What NEBB Certification Means

NEBB certifies firms that meet certain criteria, ensuring strict conformance to its high standards and procedures. Among other requirements, NEBB-certified firms must document a record of responsible performance, own a complete set of instruments required for the sophisticated techniques and procedures necessary to "fine-tune" modern environmental systems, and have a NEBB-qualified supervisor as a full-time employee.

Once having met NEBB's rigid requirements for certification, Enterprise's certification must be reviewed and renewed every two (2) years. Through the recertification procedures, Enterprise must verify that its NEBB-qualified supervisor is still on staff and that the company continues to own a complete set of instruments which are in current calibration. In addition, the Enterprise's NEBB-qualified supervisor must renew his/her qualification.


Most owners of multiple buildings will start with their highest energy consuming buildings.  A typical metric for this evaluation is determined by taking the annual utility cost (normally gas/electric) and dividing into the building square footage. For example, a 50,000 square foot Medical Office Building with a $125,000 annual utility bill has a $2.50 cost/square foot.

Another selection criterion has to do with performance of the building systems; i.e., which buildings are considered problematic from an energy systems (HVAC, lighting, compressed air, etc.) perspective? It is understood that energy will be saved as a result of retro-commissioning, but if the building owner can solve chronic performance problems at the same time (comfort complaints, process interruptions, noise, etc.), that can be a strong motivator in the building prioritization process.

Buildings whose systems are currently operated continuously will typically offer better paybacks than buildings that are operated on a standard work week schedule.

Buildings with mechanical A/C (cooling) often provide greater energy savings potential than buildings with only heating systems (except in the most extreme cold climates).

Older buildings which have experienced multiple renovations or system modifications over the years are very good candidates for retro-commissioning.

New or recently renovated buildings with DDC systems that were not commissioned as part of the original design/construction project have also proven to benefit greatly from the retro- commissioning process.


Buildings with DDC systems  and web based systems will often have the most potential for hidden problems that can be discovered through a retro commissioning process.  In addition, retro-commissioning a building with a DDC system often takes less effort (time) than retro-commissioning a building with only local controls.  The power of the DDC system can be used to trend key performance parameters over time and to view the status of multiple points and devices simultaneously.

Buildings with local pneumatic/electric controls also have great potential for hidden problems due to their lack of central reporting and/or monitoring of the distributed controllers.  The older the local controllers are, the more likely they are to be out of calibration or otherwise “broken”.

As implied above, it is more labor intensive to re-commission a building with local pneumatic/electric controls than a building with a DDC system.  Field investigation and checkout of control system operation takes considerably more time due to the absence of permanently installed monitoring equipment.  In addition, the need to install and un-install portable data loggers to graph system performance data over time is quite different than the effort to set up and download trend logs from a DDC system. 

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