Existing Building or Retro Commissioning: EB-Cx, R-Cx

Existing building commissioning is the systematic process ensuring an owner that the building and systems are optimized to perform interactively to meet the current operational needs. This includes minor adjustments through testing, adjusting and balancing (TAB) and may include remedial design/construction to accomplish this goal.

Retro-Commissioning is the commissioning of a building that has not been subject to a commissioning program. Re-Commissioning is a revisit of a building that has been previously commissioned.

The process can generally be accomplished at $0.20 - $0.90 per square foot with a savings of 5 - 30%; simple payback is commonly 1 - 3 years, depending on complexity of scope. Through application of this process the intent is improved facility operation. It consists of a five step process:

Step 1: Contract Phase

  • Negotiation of systems to undergo retro-commissioning (Retro-Cx)

Step 2: Documentation Phase

  • Initiate building metering activities configure metering devices and launch each device for measurement of gas/electrical consumption, temperature/humidity/lighting levels in various zones, measure CO2 in various locations throughout facility, and allow to trend.
  • Download trends on a weekly basis
  • Collect all as-built mechanical and electrical construction drawings
  • Inventory all mechanical systems (trace out and number each system type: supply air, return air, exhaust air, chilled water cooling, hot water heating, steam/condensate, etc.)
  • Interview various tenant representatives, building manager, maintenance representative
  • Collect and review air/hydronic (water) TAB reports
  • Review sequence of operation and points list for all control systems
  • Familiarization with building automation system and its capabilities

Step 3: Site Investigation Phase

    • Implement TAB survey of all airside mechanical systems; this will include the following activities:
      • Comprehensive air-handling unit performance evaluation (RPM, static pressures, amperage, voltage, airflow measurement of each main duct system, etc.)
      • Observe airflow at each terminal unit (diffusers/grilles – supply, return, exhaust and calibration of all VAV boxes as needed)
      • Determination of pump unit performance (RPM, differential pressures, impeller size, amperage, voltage, unit flow)
      • Measurement of each terminal flow measuring device
      • Building pressurization in various modes of operation
      • Summary of overall system performance
    • Implement control system evaluation
    • Verify sequence and correctness of operation at both the system and terminal unit level; this takes place for the following systems:
      • Air-handling system (includes the associated DX refrigeration system)
      • HVAC Zone Control (all unit heaters, exhaust fans, etc.)
    • Document all initial findings and make minor adjustments as required to fine tune the system (this may include but is not limited to: thermostat calibration, economizer damper adjustment, temperature, humidity or pressure sensor calibration)
      • Compile all results of the system analysis activities
      • Summarize all issues found and quantify with respect to energy/operations cost any minor changes made to each system
      • Summarize all issues identified but not addressed due to scope of current project
      • Propose and prioritize various changes that could potentially save additional cost in operations/energy consumption (presented in terms of initial vs. final vs. proposed and the simple return on investment – ROI associated with the modification)
    • Executive summary with final report of Site Investigation Phase findings, adjustments, results and opportunities for improvement. Any savings identified as a result of these observations and minor changes/fine tuning will be presented.
    • Meet with and review results of program with Owner
    • Owner qualifies proposed results for implementation (if applicable)

Note: It is highly recommended that Owner’s maintenance staff join the Retro-Cx team when carrying out these evaluations for future reference and potential troubleshooting activities required on building systems

Step 4: Implementation Phase

      • Establish plan for implementation of changes proposed
      • Implement changes
      • Re-commissioning of systems affected by changes

Step 5: Final Reporting Phase

      • Compile final results (eg, calculate and summarize all final energy / operations costs & compare to original baseline)
      • Training of owner maintenance staff on any altered methods of operation
      • Off season follow-up to verify conditions established