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« Codes, Regulations, and Incentives |
Table of Contents |
Conserving Systems and Equipment » |
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Commissioning |
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Commissioning is a preparatory process whereby a building is readied for operation. This includes a quality assurance process to ensure that building systems perform as intended. As buildings become more complex the importance of systematically evaluating their performance has increased. Systems commissioning can be especially critical in the case of innovative buildings that incorporate promising but relatively untested technologies.
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Contents
1.Definition
2. Use/Application
a. Established Techniques
b. Emerging Trends
3. Use an Integrated Approach
4. Resources
5. Associated Strategies
6. Case Studies |
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Definition |
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Commissioning is a preparatory process whereby a building is readied for operation. This includes a quality assurance process to ensure that building systems perform as intended. As buildings become more complex the importance of systematically evaluating their performance has increased. Systems commissioning can be especially critical in the case of innovative buildings that incorporate promising but relatively untested technologies. In recognition of this fact and because systems commissioning has been proven to be among the most cost-effective approaches to reducing energy use in buildings, fundamental commissioning of energy-related systems is a prerequisite in green building standards that have been developed in recent years.
Systems commissioning refers to:
– HVAC systems and associated controls
– Lighting and daylighting controls
– Domestic hot water systems
– Renewable energy systems
Total building commissioning (TBCx) includes mechanical systems, the building envelope, plumbing, and life safety systems. Total commissioning is therefore broader in scope than systems commissioning. Note that some aspects of total commissioning (i.e., building envelope) can be very critical to building energy performance and carbon reduction, whereas other aspects of total commissioning (i.e., life safety systems) may have less of an impact on carbon reduction. With regard to the building envelope, where an impact on carbon reduction is possible, in addition to analyzing the thermal performance of the building envelope, TBCx includes an evaluation related to air infiltration, moisture diffusion, condensation risk, and rainwater entry. Improving these aspects of building envelope performance can significantly improve the durability and long-term energy performance of building envelopes.
Systems commissioning includes planning, delivery, verification, and managing risks to critical functions. Deficiencies in design or installation can be identified using peer review and field verification. Systems commissioning typically results in higher energy efficiency, environmental health, and occupant safety and improves indoor air quality. As part of the process, preventive and predictive maintenance plans, tailored operating manuals, and training procedures are developed. Essentially, the commissioning process formalizes review and integration of all project expectations during planning, design, construction, and occupancy phases by inspection and functional performance testing and oversight of operator training and record documentation. The first step in any commissioning process is to identify a commissioning authority (CxA) for the project. The CxA is a third party, hired by the owner, that is primarily responsible for coordinating the commissioning process and for providing the project with an unbiased perspective, independent of the design or construction team. For smaller projects, it is acceptable for a CxA to be employed by a design team firm but not directly involved in the design of the project itself. For larger projects, the CxA should not be affiliated with the design team. In all cases, the CxA should have experience with projects having similar building systems, size, and budget, and should be brought onboard as early in the process as possible.
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Use / Application |
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Commissioning can take place during design, construction, and post occupancy.
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Established Techniques |
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Design Phase Activities for Both Fundamental and Enhanced Commissioning
The first step in any commissioning process is to document the owner’s project requirements (OPR). The OPR details the functional requirements of the building systems from the owner’s perspective, including facility uses, occupant comfort, and project success. Above all, the OPR should be measurable and verifiable. It is important to note that an owner may not have experience formally documenting these requirements. In this case, the CxA can conduct a workshop to facilitate the development of the OPR. In response to the OPR, the design team for the project should develop a basis of design (BOD) document that describes the system configurations and control sequences that will be implemented to meet the OPR. The BOD should include assumptions made by the mechanical engineer to design the HVAC systems, including indoor and outdoor design conditions and occupancy schedules.
The CxA will conduct design reviews in the context of the BOD. As a best practice, a CxA should be designated early enough during the design process to be able to perform an initial review prior to 50 percent construction documents (CDs). The CxA will also develop specifications for the architect to incorporate into the CDs. All of the tasks to be performed during commissioning are described in a commissioning plan developed by the CxA. This plan also describes roles and responsibilities of the entire design team in the process, as illustrated in Table 1
Construction Phase Activities for Both Fundamental and Enhanced Commissioning
Prior to the end of the design process, the CxA will develop a construction phase commissioning plan. Table 2 presents a sample project schedule taken from the PECI construction phase commissioning plan (www.peci.org). During and immediately prior to the construction phase, a CxA may review contractor submittals related to the systems that will be commissioned. After equipment start-up, the CxA conducts installation inspections, also known as “prefunctional inspections.” Once equipment is fully installed, the CxA conducts functional performance testing to evaluate performance at all sequences of operation. The CxA usually develops protocols for functional performance testing during the construction phase on the basis of project specifics and the sequence of operations developed by the controls engineer (CDs often do not provide enough detail). It is important to note that some functional testing can be performed only in certain seasons, which will usually extend the commissioning process beyond the completion of construction. At the end of the commissioning process, the CxA prepares a final report and may also prepare an operations and maintenance (O&M) manual for the project.
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Emerging Trends
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The high-performance building movement in general and various energy rating prerequisites in particular have brought commissioning more into the mainstream in recent years.
Fundamental Versus Enhanced Commissioning
The United States Green Building Council’s Leadership in Energy and Environmental Design (LEED) program also distinguishes between “fundamental” commissioning and “enhanced” commissioning. Fundamental commissioning encompasses the design and construction phase tasks discussed above. Enhanced systems commissioning includes the following additional tasks:
1. Conduct design review prior to the end of design development.
2. Review contractor submittals for energy-related systems.
3. Develop recommissioning manual.
4. Inspect operation of energy-related systems within 10 months of final acceptance and develop plan to resolve outstanding issues.
Total building commissioning recognizes and measures interrelationships between individual building components and systems that affect overall performance, occupant satisfaction, and cost.
The additional work associated with enhanced commissioning tends to result in a 15 percent first-cost premium compared with fundamental commissioning. The owner should be encouraged to assess the life-cycle implications of enhanced commissioning as part of the decision-making process.
After Commissioning
Periodic re-commissioning is a process intended to ensure persistent energy savings over the life of a building by reapplying previously conducted commissioning tests. Re-commissioning may be performed every few years or even continuously, depending on the complexity of the building. Often, a major capital improvement to a building can trigger re-commissioning activities. The California Commissioning Guide outlines the following other indicators that can be used to assess when re-commissioning is appropriate for a particular building:
– Is there an unjustified increase in energy use?
– Have comfort complaints increased?
– Is building staff aware of problems but without the time or in house expertise to fix them?
– Has control programming been modified or overridden to provide a quick fix to a problem?
– Are there frequent equipment or component failures?
– Have there been significant tenant improvement projects (buildouts)?
Recommissioning activities can be performed by an independent CxA or by building maintenance staff, if they have the training, time, and resources. The first step in any recommissioning process is to review the OPR developed as part of the original commissioning process for the building. If the requirements of the building have changed, the OPR should be updated to reflect the changes. Functional performance tests of equipment are then conducted to evaluate whether systems are performing as designed. Systems performance over time may be evaluated based on any data collected and stored by the building management system or utility bill tracking.
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Use an Integrated Approach |
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A new way of thinking must be adopted in order to meet the goal of reducing carbon emissions associated with buildings. Your solutions can begin by integrating four possible methods. None works alone, and they are not all relevant in considering every strategy. However, considering the following tactics is necessary:
- Reduce the overall energy use in your building
- Specify energy-efficient equipment and technologies
- Use renewable strategies and purchase green power
- Educate building owners, operators, and occupants
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Cost and Benefits |
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Portland Energy Conservation Inc., Lawrence Berkeley National Laboratory, and Texas A&M University have performed a rigorous analysis of the costs of commissioning. Results from this study are illustrated in Figures 1 and 2. Median commissioning costs were $0.27 per square foot with existing buildings and $1.00 per square foot with new construction. With existing building commissioning, this study documented paybacks of less than one year in the majority of the 100 buildings evaluated. The average payback for new construction commissioning was 4.7 years.
Commissioning costs per square foot tend to be higher in more complex buildings such as hospitals and laboratories. However, as a result of their relatively high energy intensity, paybacks for commissioning also tend to be lowest in these buildings. For existing buildings in this study, the median whole-building energy cost savings associated with commissioning was 15 percent. The carbon reduction potential associated with commissioning in existing buildings is likely to be of the same order of magnitude as this energy reduction: A 15 percent reduction in energy use will translate into (roughly) a 15 percent reduction in carbon.
As previously mentioned, fulfilling the LEED enhanced commissioning requirements tends to result in an increase in first cost of roughly 15 percent compared with fundamental commissioning. Nonenergy benefits of commissioning were also evaluated as part of the above-cited study and are described in the chart below. Although nonenergy benefits will not necessarily translate into carbon reductions, they can be important to convincing decision makers of the value of commissioning to their projects. |
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Last modified at 2/26/2009 10:25 PM by jamie nace
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