Whether or not owners should invest in Building Commissioning has become a rather important and complex decision over the years. First, owners need to resolve their commissioning needs, comparing the costs and benefits to their budget. Since buildings can be commissioned several different ways, they must then choose the extent of commissioning that is most appropriate for their facility, including Installation Commissioning, System Commissioning, or more limited methods such as ATC System Verification.
While Full Installation Commissioning can be an involved process, it should not be totally ignored. Most facilities, however, don’t require such exhaustive commissioning. Commissioning of individual building systems, especially HVAC systems, is usually adequate and is in fact becoming increasingly important.
Commissioning of an Installation is defined by the 1995 American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Handbook as the “process for achieving, verifying, and documenting the performance of buildings to meet the operational needs of the building within the capabilities of the design and to meet the design documentation and the owner’s functional criteria, including preparation of operator personnel.”
The process begins in the pre-design phase of a project and is not complete until the post-acceptance phase. Building commissioning parameters, responsibilities, and documentation requirements are developed during the pre-design phase. During the design phase, commissioning requirements for all building systems (HVAC, plumbing, electrical, fire protection, communications, and/or security systems) are developed to include the following data:
• Design criteria and assumptions
• Description of each system to be commissioned, including the intended operation and performance
• Verification requirements
• Maintenance requirements
Pre-start-up inspections should be performed upon completion of construction, and Test and Balance work should begin after the systems are accepted for start-up. After systems have been tested and balanced, the functional performance testing of systems begins, including such tasks as:
• Equipment and subsystem functional performance tests
• Verification and documentation
• Corrective measures
• Acceptance documentation
• Operator training
• Final acceptance
After the commissioning needs are resolved, a member of the project team should be appointed “Commissioning Authority.” This role can be filled by someone from the owners’ staff, the construction manager, design professional, general contractor, test and balance contractor, or commissioning specialist.
Since the cost of Installation Commissioning depends on the size of the project and the number of systems involved, there is no reliable data on its added cost to a project. The basic intent of commissioning is to recover the capital investment over the life of the system through management, efficiency, and user satisfaction.
System Commissioning is a cost-effective alternative to full Installation Commissioning, allowing owners to focus on specific systems instead of every system in the building. The 1995 ASHRAE Handbook defines it as the “process for achieving, verifying, and documenting the performance of that system to meet the operational needs of the building within the capabilities of the design and to meet the design documentation and the owner’s functional criteria, including preparation of operator personnel.”
In this process, one or more building systems is selected for commissioning. This option is typically utilized when the added cost of Full Installation Commissioning can not be justified. The process is the same, beginning at pre-design and continuing through construction.
For instance, if a determination is made that the HVAC system should be commissioned, each of its subsystems (e.g., fans, pumps, airflow, water flow, heating/cooling capacities, and controls) would be involved in the process.
As HVAC systems have grown in sophistication, Commissioning has become increasingly important. Direct Digital Control (DDC)—a popular method for control of HVAC systems—makes extensive use of software, much of it customized for a particular facility. Therefore, it has never been tested for its specific application and must be debugged if the system is to function as intended.
When HVAC problems do occur after start-up, the immediate – and justified – question posed by the owner is “who is responsible?” If the problem is related to control system software, and in the vast majority of cases it is, then the question becomes difficult to answer. The control contractor is expected to repair the software, but unfortunately does not usually possess the expertise to locate the problem. While control contractors are knowledgeable of system installation and programming, they are not systems engineers, and thus do not necessarily know how the system is designed to operate. Who does? The design professional. And this brings us to catch-22. In the past, excluding very large and complicated systems, pneumatic control systems were less sophisticated and required less need for System Commissioning. As a result, Owner/Engineer Agreements were written in such a manner that did not include commissioning as part of the engineer’s responsibilities. These standard agreements are still being used today, including those by AIA and EJCDC.
According to these agreements, the engineer has no responsibility to commission or verify proper control operation. If system control problems arise, the control contractor may create more severe problems by attempting to fix the system without the design professional’s input. HVAC System Commissioning—performed by the design professional—alleviates this problem.
When dealing with HVAC systems, the owner has another option to help ensure proper operation of the systems without the need for the exhaustive and sometimes expensive method of Systems Commissioning: ATC (Automatic Temperature Control) System Verification. This option utilizes one of the major steps in the commissioning process to confirm system operation and concentrates on the controls component of the HVAC system. After normal contractor start-up and completion of the test and balance work, the control system sequences are verified by simulating the various operating conditions of the system and making sure the sequences operate as intended.
In instances where HVAC systems do not function as intended, investigation frequently reveals the building control systems to be the culprit. Corrective action must be taken to verify that the systems are operating as designed and specified.
ATC System Verification is less costly than HVAC System Commissioning, but also results in a control system that functions correctly. Plus, a direct hookup to facilities via modem allows the design professionals to monitor and troubleshoot a building’s Direct Digital Control system from their office. This has proven invaluable in the system verification process because it allows the design professional to watch the system in operation while keeping the cost of the process to a minimum.