The Case for Commissioning
Long-term energy efficiency and system reliability offer life-cycle cost benefits
Except for certified “green” buildings, where it is one of the requirements for certification, full-scale, integrated commissioning of new buildings is still rare, despite Department of Energy studies that show commissioning substantially reduces energy costs. There are several reasons why. Commissioning can be expensive. Owners and facility managers assume testing of individual pieces of equipment by manufacturers is sufficient. And many developers of speculative properties intend to pass on utility bills to tenants and therefore view commissioning as unnecessary.
But in an era in which energy prices are unstable and when the increasing complexity of building systems makes reliability a paramount concern, these rationales look less sound. Even developers of spec buildings have good reason to question the “let the tenants pay for it” attitude that’s guided them in the past, because a building’s energy efficiency is likely to become an ever more important factor in prospective tenants’ decisions on whether or not to lease space.
The wisdom of weighing first costs against life-cycle costs to determine commissioning’s cost-effectiveness is clearer than ever. At present, the costs of operating and maintaining a mechanical system over its life are at least five times more than all the costs associated with mechanical system design and installation. When you add the possibility of steep or persistent energy price hikes into the mix — and when you consider how commissioning improves both energy efficiency and long-term reliability — the initial cost begins to look a lot less onerous.
System Interaction Is Key
Why does commissioning augment energy efficiency and system reliability? Because the key to controlling energy usage and ensuring reliability has to do with the optimal interaction of systems — including mechanical and electrical systems’ integration with the building management system. It’s exactly this interaction that commissioning examines and fine-tunes, which is why manufacturers’ evaluations of individual pieces of installed equipment aren’t sufficient. That is why groups that certify green buildings, which stress the performance of the building as a whole, insist on commissioning.
The question of who should do the commissioning is a critical and tricky one. Should commissioning be performed by the consulting engineer responsible for designing the systems or by an independent commissioning agent? Good arguments can be mounted for either option. Having the systems’ designer also test and evaluate their performance may raise conflict-of-interest issues. On the other hand, who can better understand whether systems are interactively performing as intended than the engineering firm that designed them? One way to reduce possible conflict of interest is a new, design-build-operate-maintain model in which commissioning is conceived of as an ongoing process and in which some portion of the compensation due the consulting engineering firm, which both designs the systems and manages their operation, is tied to system performance after occupancy.
Essential Aspect of Design
Today, building systems and the ways in which they interact are so complex that, to be truly valuable, commissioning is being redefined as an integral element in the design process. When commissioning is treated as an essential aspect of design — and when commissioning begins even as early as a project’s programming phase — owners and managers have a chance to help select systems that best address their needs. For example, owners and managers have a solid understanding of their O&M staff’s capabilities. That knowledge should be brought to bear on the selection of systems, so that there’s a good match between staff size and skills and the systems’ operational requirements.
Further, it’s essential that some senior facility staff participate in the commissioning process during functional testing. This not only ensures that top-level operations people will be thoroughly trained in all the systems and will understand their interaction with one another and with the building management system, but it also involves these personnel in the creation of system documentation — one of commissioning’s most important benefits. Over the long haul, system reliability is underwritten by the library of documents — records, as-built drawings, O&M manuals — produced during the commissioning process, which serve as references and training tools over the building’s entire life cycle.
Robert Haughney is director of Cosentini Facility Management, a unit of Cosentini Associates, New York City.