The Commissioning Process

The commissioning process is defined by ASHRAE Guideline 0-2013 The Commissioning Process as “a quality-oriented process for achieving, verifying, and documenting that the performance of facilities, systems, and assemblies meets the defined objectives and criteria.” The commissioning process encompasses all components of the building, including the building envelope, electrical, fire protection, life safety, security, data and telecommunications, plumbing, and HVAC systems.

HVAC Commissioning


Commissioning is normally facilitated by the commissioning authority (CxA) who is often contracted directly by the owner in order to function as an impartial third party throughout the commissioning process. The CxA develops and implements the commissioning plan; develops the commissioning specifications; confirms incorporation of the commissioning specifications into the contract documents; performs commissioning activities during the construction, and occupancy and operations phases; and documents all commissioning process activities in the commissioning report.

It is important to note that commissioning is not an activity that occurs at one point in time-at the completion of construction-rather, it is a process that begins in the predesign phase and continues into the operations and maintenance of the commissioned systems. Proper commissioning ensures that the objectives and criteria originally established by the owner for the project are actually implemented by the design, construction, operations, and maintenance teams.

Pre-Design Phase

The commissioning process begins in the pre-design phase when the owner establishes the goals for the project. These goals are communicated to the CxA and design team who assist the owner in preparing the Owner’s Project Requirements (OPR). The OPR defines the project goals, such as those for energy efficiency, sustainability, functional requirements, cost considerations, and operations and maintenance requirements.

The CxA develops the preliminary commissioning plan with input from the design team to describe the commissioning process activities and how the activities will be implemented by the design, construction, operations, and maintenance teams.

Design Phase

During the design phase, the design team incorporates the goals of the OPR into the Basis of Design (BOD)-a narrative description of the project that identifies how the project will address each of the items stated in the OPR. The BOD becomes the guiding document in the preparation of the contract documents (drawings and specifications). The BOD includes a description of the design parameters; systems and assemblies; applicable codes, standards, and guidelines; and specific manufacturers to be used as the basis of design. Once complete, the contract documents should incorporate all of the items identified in the OPR and BOD. The OPR and BOD may be revised during the course of the design, primarily in response to the owner’s directives.

During the design phase, the CxA:

  • Performs a focused review of the design documents to ensure that the OPR and BOD have been addressed
  • Develops complete commissioning specifications for all commissioned systems, including a description of the commissioning process; deficiency resolution; installation, start-up, and prefunctional checklists; functional testing requirements; and acceptance criteria.
  • Ensures that the commissioning specifications are incorporated into the contract documents by the design team.
  • Finalizes the commissioning plan for the construction and occupancy and operations phases.

It is not the CxA’s responsibility to ensure that the design complies with applicable codes, standards, and guidelines, that is, the responsibility of the design team.

Construction Phase

After bidding and award to the successful contractor, the project moves into the construction phase where commissioning continues with submittal review; issues log; deficiency resolution; installation and start-up checklists; prefunctional checklists; review of the testing, adjusting, and balancing (TAB) execution plan; review of the TAB report; verification of a sampling of TAB results; and functional testing. The construction phase is completed at the point of substantial completion.

During the construction phase, the CxA coordinates the entire commissioning process including scheduling of commissioning activities to coordinate with the delivery, installation, and start-up of equipment. The CxA also ensures that the contractor completes all necessary installation, start-up, and prefunctional checklists. The CxA finetunes the functional testing requirements for the commissioned systems with input from the design team and contractors. The commissioned systems must be balanced and confirmed to be ready for testing before any functional testing begins.

The functional testing of the commissioned systems is performed by the contractor under the direction of the CxA. It is the responsibility of the CxA to observe the performance of the commissioned systems and document the results in the commissioning report.

Submittal Review

Although the design team has the primary responsibility for ensuring that the submittals address the design requirements, the CxA also confirms that the OPR have been met and that appropriate commissioning documents, such as installation, start-up, and prefunctional checklists, have been submitted and are appropriate for the commissioned equipment and systems. The CxA also reviews the TAB execution plan submittal.

Issues Log

Throughout the course of construction, the CxA maintains an Issues Log, which is a running log of issues that are identified by the owner or any member of the design or construction team, which must be addressed by the contractor. Each issue is assigned a unique identification number, the date that it was identified and by whom, a description of the issue, who is responsible for the corrective action, the corrective action that was taken and by whom, and when the issue was finally closed. The Issues Log serves as a record of issues that were identified during construction and how they were ultimately brought into conformance with the contract documents.

Deficiency Resolution

Once a deficiency has been identified, it may require the design team to issue a Corrective Action Report (CAR). Each CAR will be assigned a unique identification number, will list the deficiency and the system it is associated with, will include a description of the deficiency and the corrective action recommended by the design team member, will include documentation by the contractor that the corrective action was completed successfully, and will include verification by the CxA that the corrective action was completed. The CxA may assist with problem solving and resolving deficiencies, but ultimately that responsibility resides with the contractor and the design team.

Installation and Start-Up Checklists

The CxA works with the contractor in completing the installation and start-up checklists for each piece of commissioned equipment and signs-off on the completed checklists. The installation and start-up checklists may be standard checklists developed by the equipment manufacturer, or may be custom checklists developed by the CxA and the design team.

Prefunctional Checklists

Prefunctional checklists, or system readiness checklists, are developed by the CxA as a means of documenting that all components, equipment, and systems are ready for functional testing. Prefunctional checklists are completed by the contractor and submitted to the CxA prior to functional testing.

Preliminary Control System Functional Testing

Prior to performing functional testing of the HV AC systems, the control system must be functionally tested to a level sufficient to demonstrate that it can be used for testing, adjusting, and balancing of the HV AC systems.

Testing, Adjusting, and Balancing (TAB) Execution Plan

The TAB execution plan is prepared by the TAB contractor and explains the means and methods that the TAB contractor will utilize in testing, adjusting, and balancing the HVAC systems. The CxA will review the TAB execution plan before testing, adjusting, and balancing begins.

Testing, Adjusting, and Balancing (TAB) Report

After the prefunctional checklists for all HVAC systems are complete, and the preliminary functional testing of the control system is complete, the TAB contractor tests, adjusts, and balances the HVAC systems in accordance with the TAB execution plan in cooperation with the HVAC contractor and the control system contractor. Once complete, the TAB contractor submits the final TAB report to the mechanical engineer for review and approval. Once approved by the mechanical engineer, the CxA will approve the TAB report after field-verifying a sampling of the TAB results with the TAB contractor. Deficiencies in the TAB report discovered by the CxA during the field-verification are identified either in the Issues Log or through CARs and must be addressed by the TAB contractor. If substantial deficiencies in the TAB report are identified, the CxA may increase the sampling of TAB results for follow-up field verification.

Functional Testing

Once the prefunctional testing of all components, equipment, and systems has been completed, and the final TAB report has been approved by the CxA, functional testing of the HV AC systems can begin. In general, functional testing is performed from simple to complex: from the component level to the equipment level, from the equipment level to the system level, and from the system level to the intersystem level. Functional testing on the component and equipment levels ensures that all parts of the HVAC systems are functioning individually before the larger HVAC systems are functionally tested. Functional testing on the intersystem level involves multiple systems, such as the HV AC and fire alarm systems, and can only be performed once all such systems have been individually tested.

During functional testing of the HVAC systems, the CxA verifies that the component, equipment, system, and intersystem functional testing procedures developed during the design phase and fine-tuned during the construction phase are successfully executed. The actual functional testing of the commissioned systems is performed by the contractor and is documented by the CxA. Items of noncompliance are identified by the CxA in the Issues Log or through CARs and the systems are retested by the contractor until satisfactory performance is achieved.

After functional testing is complete and the initial stage of occupancy begins, the CxA reviews a sampling of trend logs for various HVAC systems to ensure that the systems continue to function properly in all modes of operation.

Seasonal commissioning may also be required, which includes functional testing of HVAC systems under actual seasonal conditions. For example, an airside economizer mode of operation cannot be functionally tested in the extreme outdoor temperature conditions of winter and summer. Functional testing of this mode of operation will require outdoor temperatures in the 50s F. Also, heating systems cannot be adequately tested in the summer, nor can cooling systems be adequately tested in the winter.

Occupancy and Operations Phase

After substantial completion of the project, the design professionals, CxA, and contractors ensure that the owner is properly trained in the operations and maintenance of the commissioned systems. Along with the design team, the CxA reviews and approves the closeout documents, such as the operations and maintenance manual, preventive maintenance plan, and record drawings to ensure compliance with the project specifications.

Commissioning continues beyond owner acceptance of the commissioned systems through the warranty period with ongoing monitoring of the commissioned systems by the CxA, including a 10-month review of building operations. After 10 months of occupancy, the CxA should review any outstanding issues related to the original and seasonal commissioning. The CxA should also interview the facility staff to identify concerns with the operation of the HVAC systems, determining which items should be addressed by the contractor under warranty. The CxA should also review the preventive maintenance plan with the facility maintenance staff and update it as required. Finally, the CxA documents all commissioning process activities in the final commissioning report that is submitted to the owner. Although the formal commissioning process ends with the final commissioning report, commissioning should continue throughout the life of the facility to ensure on-going compliance with the OPR.


HVAC Design Sourcebook, Angel, W. Larsen