The LEED certification processrecognizes the importance of building system commissioning by making it a prerequisite in attaining compliance. What is equally important, if seriously overlooked in the process (as well as overlooked for most construction jobs), is third-party testing, adjusting, and balancing (TAB) of air and water systems.
Before a system is demonstrated to the commissioning team, the HVAC systems will need to be adjusted and balanced to the flow quantities specified in the contract documents. This scenario is analogous to an automobile coming off the assembly line functioning and all systems interacting per manufacturer’s specification. The automobile meets those criteria at that point in time, but until the car is tuned up, the vehicle won’t be operating at peak performance. Without TAB, a building system can be demonstrated as operating and interacting per design but probably won’t be functioning at peak performance. And isn’t that what LEED is all about? Energy-efficient performance is the cornerstone of this process.
Historically, the TAB contractor has worked for the HVAC trade contractor under the title "independent TAB subcontractor." Now, think about this. How independent do you think the TAB contractor is when he is receiving payment for his services from the firm that he is doing the work for?
Another problem with the processis that the design engineer usually writes the TAB specification without truly understanding the needs, requirements, and procedures that a TAB contractor should be following. They will specify TAB requirements based on industry guidelines, but TAB contractors do not necessarily follow these guidelines, which are their own industry standards. The main reason for this omission of tasks is usually price-driven with the TAB contractor being selected on low price.
Like commissioning, TAB is “documentation and verification.” The TAB contractor is frequently hired late in the construction process; however, the TAB engineer should be contracted during the construction document phase of the design. Without a 3rd party TAB firm beginning in the design phase, the TAB firm will not have the opportunity to complete a comprehensive review of the contract documents, create system flow diagrams, or assess system installations prior to starting the balancing process in construction. All of these items, along with providing “design to actual installation” field notes, should be completed by the TAB firm, in addition to the required final TAB report. If these tasks are not completed, then the documentation and verification of the systems will fall far short of the TAB process goals.
This problem is further compounded by TAB firms who frequently become number-takers instead of system technicians capable of tuning up air and water systems. To quote Mr. W. David Bevirt, P.E. from the National Environmental Balancing Bureau’s Environmental (NEBB) manual, Environmental Systems Technology, he states, “Testing, adjusting, and balancing personnel no longer can be just instrument readers; they must understand fully how to perform their work. Furthermore, they must understand at least the fundamentals of how these systems function, and use this knowledge to determine what is malfunctioning and how to correct it.”
The solution to this missing linkin the LEED process and the building process is to have the TAB work completed by a third-party TAB firm. For more on this, click here for my suggested third-party TAB Request for Proposal and let me know what your thoughts and experience with third-party TAB firms.
For additional information on this topic, click on to "Tomorrow’s Engineer" columns Jump-Starting The TAB Process (December 2005) and More On Jump-Starting The TAB Process (February 2006).