|
Commissioning Uncovers Optimization Opportunities HVAC and Air Quality are Prevalent Motivators
January, 2008
Research from Lawrence Berkeley National Laboratory
Few buildings perform as intended. Numerous pervasive and chronic performance deficiencies stem from design flaws, construction defects, malfunctioning equipment and deferred maintenance.
These deficiencies have a host of ramifications, ranging from equipment failures to compromised indoor air quality and comfort to unnecessarily elevated energy use. For similar reasons, energy-saving design concepts for new buildings or retrofits for existing ones often fail to deliver predicted savings.
In response to a growing awareness of these problems, quality assurance techniques collectively known as commissioning have emerged over the past two decades to address deficiencies in new construction and existing buildings alike. In its highest form, the commissioning process treats the building as a system, and uses inspection and functional testing to implement measures designed to optimize overall energy and non-energy performance. Energy oriented commissioning is one of the newest fields within the overall energy management arena, offering greater and more cost-effective energy savings than many traditional "hardware" strategies.
Commissioning has far broader relevance for energy management than simply optimizing energy-efficient systems. In new and existing buildings alike, energy efficiency can be enhanced in two major ways - either by ensuring and maximizing the performance of specific energy efficient measures, or by correcting problems that can cause unnecessarily elevated energy use in conventional systems. Historically, the original focus of building energy commissioning was centred on the former - i.e. limited to specific energy efficient measures - but has expanded to address the significant opportunities in typical buildings.
While individual building components are commonly tested or rated in a standardized factory setting (e.g. COP ratings for heat pumps), integrated assemblages of such technologies - which include important connective systems such as thermal distribution or controls systems - are rarely tested in the field.
In its broadest sense, the practice of commissioning involves a series of systematic procedures and tests to ensure that new and existing building processes, technologies and systems are applied and function in an integrated fashion as intended by the designer and desired by the owner. However, in practice, commissioning is rarely comprehensive (e.g., focusing only on specific pieces of equipment or, in the case of new construction, hampered by a lack of budget or late commencement of the process.)
SYSTEMS-LEVEL PERSPECTIVE
There is a continuum across which both new construction and existing buildings commissioning techniques and perspectives are relevant. For example, when a new HVAC system is installed as a retrofit to an existing building, many of the issues normally associated with new construction commissioning apply.
As distinct from routine operations and maintenance, the particular power of commissioning is in looking at systems-level problems, e.g., interactions between control systems and HVAC equipment. The scope of commissioning can span all aspects of buildings, including security, safety, structural integrity, indoor environmental quality and energy performance.
While commissioning is often done primarily for non-energy reasons - e.g., to address indoor air quality concerns - it is not necessary to decouple the two. For example, in case studies of commissioning activities in existing schools in
Minnesota that were primarily intended to address indoor environment concerns such as inadequate air supply, energy objectives were integral so that increased ventilation did not create a burdensome energy penalty.
While energy savings are not always the prime motivator of commissioning, energy-using systems are often at the root of problems - e.g. comfort complaints - that commissioning providers seek to remedy. Commissioning costs thus typically encompass measures that do not save energy, yet the economic value of non-energy impacts is rarely quantified. This leads to an underestimation of the cost effectiveness of commissioning.
Some view commissioning as a luxury and added cost, yet it is only a barometer of the cost of errors promulgated by other parties involved in the design, construction or operation of buildings. Commissioning agents are just the messengers; they are only revealing and identifying the means to address preexisting problems.
As technologies, controls and their applications change and/or become more complex in an effort to capture greater energy savings, the risk of under-performance will rise and, with it, the value of commissioning. Indeed, innovation driven by the desire for increased energy efficiency may itself inadvertently create energy waste if those systems are not designed, implemented and operated properly. The ultimate impact of energy efficiency research and development portfolios, as well as deployment programs, lies in no small part in the extent to which they are coupled with cost-effective quality assurance.
EVIDENCE OF SAVINGS
In 2004, researchers with the Lawrence Berkeley National Laboratory, Portland Energy Conservation Inc., and the Energy Systems Laboratory at Texas A&M University assembled and analyzed evidence from 150 existing buildings and 74 new construction projects - examining real world data on the energy and non-energy impacts and cost-effectiveness of commercial building commissioning.
In total, these buildings exhibited approximately 7,000 physical deficiencies. HVAC systems presented the most problems, particularly air distribution systems. The most common correction measures focused on operations and control.
Across the sample of 150 existing buildings, researchers found median whole-building energy savings of 15% (average of 18%) and a corresponding payback of 0.7 years. Median savings were approximately $45,000 per building (in 2003 US dollars) and ranging as high as $1.8 million.
The median payback time for the 74 new construction cases was 4.8 years. Quantifying energy costs savings for new construction is confounded by the lack of baseline data. Accounting for non-energy impacts can drastically reduce these payback times to, or below, zero in many cases.
Best results were seen among energy-intensive facilities such as hospitals and laboratories. Still greater potential is inferred since the scope of commissioning rarely spans all fuels and building systems in which savings may be found. Not all commissioning recommendations are implemented and significant first-cost and ongoing non-energy benefits are rarely quantified.
RISK MANAGEMENT
Commissioning is perhaps best understood as a form of risk management. At the individual facility level it helps ensure that funds are spent wisely and that the intended energy savings targets are achieved in practice.
At the regional or national level, commissioning essentially ensures and safeguards macro-level goals for energy savings and other benefits such as reduction of greenhouse gas emissions. The ultimate efficacy of energy efficiency research and development portfolios, as well as deployment programs, lies in no small part in the extent to which they are coupled with quality assurance in design and delivery.
It is important not to view commissioning in isolation, but rather as part of an integrated strategy for improving building energy performance. Commissioning interoperates with traditional operations and maintenance, tune-ups, diagnostics, end-use monitoring and the implementation of the entire spectrum of energy efficiency measures.
Performance monitoring and diagnostics are particularly important. One reason commissioning issues occur is that building operators are unaware that problems exist.
An economizer damper may be stuck or a variable-frequency drive control may be disabled, limiting efficient operations and causing energy waste. New emerging technologies and ongoing research to develop performance monitoring and diagnostics tools offer the capability to detect and diagnose the root cause of such problems.
Improved performance monitoring systems are needed to ensure critical measurements are available to detect problems. Numerous techniques for fault detection and diagnostics have been explored, including neural nets, physical dynamic models and simple engineering rules. New information technology and web-based energy information systems offer improved performance monitoring capabilities and platforms to host diagnostic tools.
The preceding article is excerpted from The Cost-Effectiveness of Commercial-Buildings Commissioning by Evan Mills, Hannah Friedman, Tehesia Powell, Norman Bourassa, David Claridge, Tudi Haasl and Mary Ann Piette. The complete report is available through the Continental Automated Building Association's INFORMATION SERIES. For more information, see the web site at www.caba.org.
|