Linking commissioning, TAB to deliver better buildings
- Know that early involvement of the CxP improves the reliability that project goals are identified and that the building systems have the ability to meet those objectives.
- Learn how the TAB contractor works with the installation contractors and, ultimately, the commissioning team.
- Understand that when the TAB contractor and the CxP work together as a team, under the same contract, then the building project is optimized.
Commissioning professionals along with testing, adjusting and balancing contractors provide a quality assurance service during the design and construction of a building. Each group covers a different aspect of the building process. When the two groups work together, the results can greatly benefit not only the owner and end user with a better performing building, but savings and efficiencies also can be realized by the construction team.
Commissioning professionals generally grow out of the mechanical, electrical and plumbing design groups, where their expertise and familiarity derives from the engineering and design family. They are well–versed in documenting a client’s needs for the new facility, selecting the appropriate equipment and developing the plans and specifications that can be bid by the contractors and built to meet those needs.
CxPs could be considered a relative of the “design family.” Similarly, the TAB contractor can be considered close kin to the sheet metal and piping contractors. They work with the mechanical contractors to test, adjust, measure and validate that the systems perform as the design intends. They also calibrate the control systems to ensure the flow readings are accurate along with damper or modulating valve positions, all of which will influence how the building systems react to maintain the desired building environmental conditions. TAB contractors can be considered a relative of the “construction family.”
Most organizations like the Building Commissioning Association, ASHRAE and the U.S. Green Building Council all recommend that the CxP be brought into a project early in the design process to take advantage of their knowledge and experience. When the TAB contractor is included in the early system reviews, their practical experience and knowledge compliment the CxP’s design review. They are familiar with what is needed to properly adjust or balance complex systems, along with the necessary volume dampers, flow meters and control devices. It is less costly to modify or make minor revisions before having the project under construction. This is the most efficient use of the commissioning design review process and it provides an additional level of confidence that the design on paper will fulfill the desired intent.
Detailing the workflow
The TAB contractor primarily focuses on measuring and adjusting each individual flow rate of air and/or water through equipment designed and purchased for the project. They adjust the equipment and balance flow rates to meet the design and the flows indicated on the drawings. More often than not, they have a large quantity of elements within a new building that have to be tested, adjusted and reported. Rarely do they have the time built into their contract to review and consider all the sequences of operation, all the components and how the overall building is going to be used. When TAB work is married to commissioning; these considerations are discussed and their respective insights help both groups understand the intention of the overall building operation.
Once the project is under contract, as construction progresses, the CxP is responsible for keeping the quality assurance milestones of the project in front of the construction team. This is achieved by dovetailing in the installation verification, system startup, testing and balancing and final commissioning tasks into the construction schedule.
As with the design review phase, during construction the goal is to discover potential problems, document them and bring them to light for the commissioning team to resolve.
The commissioning team includes the owner, engineer of record, construction manager, MEP subcontractors, the controls contractor, TAB contractor and any specialty consultant on the project. The CxP documents and maintains a list of issues. This helps to ensure that they will be addressed including issues discovered during the testing, adjusting and balancing work. More often than not, the resolution of an issue requires several members of the Cx team to coordinate a solution.
TAB work is an instrumental step before beginning the systems functional testing that is usually thought of as commissioning. The systems need to be operating and moving air with heating hot or chilled water flowing in order to demonstrate to the CxP that the system actually heats or cools the space when commanded to. If the TAB contractor determines the fan is running at full capacity, but does not move the volume of air the designer specified, then the CxP documents the deficiency and it is then up to the engineer to resolve the issue.
Many times, the CxP is viewed by the construction group as someone coming onto the site that invades their world to point out everything they can find that is wrong. The CxP does not produce a product, or actually operate equipment. They witness in a systematic forensic approach, the operation of building systems to ensure they work in accordance with the design intent. TAB contractors work closely with the mechanical and controls contractors and are usually the first to identify problems or potential problems with equipment. The TAB work is integral to a successfully commissioned building.
A marriage of the TAB and CxP activities come from opposite sides of the design and construction spectrum, and involves working together to fill gaps that may occur between the design process and construction completion. The TAB and CxP both work as an advocate for the owner’s best interest. When the general contractor or mechanical contractor holds the TAB contract, there may be a conflict of interest where some deficiencies may go unreported or are included in the balance report, but unless the engineer received the report and acts to rectify the problem, it goes unnoticed.
Together the TAB contractor and CxP partner in checking both theoretical (during design review) and actual operation (during the TAB phase) of the equipment for the building. The building owner reaps the fruit of this union as the building occupants remain comfortable, while building systems begin their new life in their proper condition.
Most buildings eventually get commissioned by testing, adjusting and balancing until the complaints stop. However, there are many benefits to starting the commissioning process early with the TAB contractor onboard, in order to ensure that systems are operating and fully tested before the owner taking occupancy. This will ensure the honeymoon between the owner and building will continue for years to come.