Continuous Optimization=>Re-Commissioning

Tasks that are common to both Re-Commissioning and Retro-Commissioning an existing building were outlined under Services for Continuous Optimization. This section further defines the approach that we take to Re-Commissioning an existing building. A definition of Re-Commissioning is as follows:

Re-Commissioning: ASHRAE Guideline 0-2005 Definition

An application of the Commissioning process requirements to a project that has been delivered using the commissioning process: this may be a scheduled re-commissioning developed as part of an ongoing commissioning process, or it may be triggered by use change, operation problems, or other needs.

The Re-Commissioning process is usually applied to a building whose systems are in a reasonable state of repair. The building has a Building Automation System that is functional but is in need of a "tuneup".

The primary objective is to identify "low hanging fruit" that can be "harvested" with little or no capital expenditure.

To be effective in Re-Commissioning a building, the Cx Authority must be very knowledgeable in the design of HVAC systems and Direct Digital Control (DDC) systems. The CA must also have "hands-on" experience working with DDC systems both at the Operator Work Station and at the distributed stand-alone controller levels. Experience with programming sequences of operation, tuning control loops, setting up trend graphs, and interpretting the results of those graphs will enable the CA to understand exactly how the building systems are performing compared to their original design intent. Field experience with Testing and Balancing and the ability to spot check problem areas enables the CA to determine when a diffuser is perfoming above or below design airflow quantities. The same is true for chilled water flow and heating water flow for coils in central air handling units or terminal units.

The CA will:

• Determine where room temperature sensors are not controlling the space temperature well. The sensors may be out of calibration, they may be located above a coffee pot or a copy machine, or they may be drafted by airflow from a diffuser that is blowing conditioned air directly at the sensor.

• Sometimes the sensor may be located across a partition wall that was installed after the original project was built.

• Identify opportunity for improvement by tightening up control loops, adjusting equipment runtime schedules, optimizing occupied room temperature schedules and tweaking setup and setback schedules for unoccupied periods.

• Document findings and recommendations. Categorize quick fix measures versus those requiring capital funding.

• Upon contract award: work with DDC contractor to implement recommendations or make programming changes yourself if capable of doing so.


• Improve occupant comfort

• Increase indoor air quality

• Reduce employee sick days

• Lower energy consumption and costs

• Mitigate CO2 footprint

• Reduce maintenance costs

• Lengthen equipment life expectancy