ASHRAE Journal - January 2009 - (Page 27) year if applied to the same building. But a hidden cost is that a walkthrough audit rarely provides sufficient data to describe the scope of work for implementation. Assuming that this work scope development, whether done by an engineer or by a designbuild contractor, might cost an additional $5,000, the ratio of audit-plus-work scope costs to annual cost savings is 0.42, or almost one half as cost effective as the comprehensive audit. Significantly, the comprehensive audit report also presents six improvements that were evaluated and could provide further savings, but that do not meet the positive life-cycle cost test. These include chiller replacement, roof insulation, replacing electric heat in the core of the building with a gas furnace (due to the high cost of electricity relative to gas), and service hot water improvements. While helping to prioritize recommended improvements (on the basis of estimated installation cost, estimated annual savings, estimated useful life, non-cost tradeoffs, and more), the comprehensive audit significantly assists the owner in not making poor economic decisions by explicitly showing the results for nonrecommended improvements. Meanwhile, the owner is provided with useful information that might tip the scales to proceed with a nonrecommended improvement, if the complete picture that portrays non-cost issues (health and safety, comfort, equipment nearing end-oflife, etc.) along with energy savings for a particular improvement, add up to justification for implementation. Structured Techniques • • • • description and list the improvements planned for evaluation. This essentially jump-starts the final report; more important, it allows a supervisor or peer to identify possible missed opportunities early on. By identifying all opportunities that need analysis up front, the analysis will not need to be repeated after the report is finished, which is much harder than if missed improvements are identified early. Calibrate energy models against utility bills before modeling improvements. In modeling, account for interactions among improvements. Describe non-cost trade-offs of each improvement, such as health and safety issues, comfort impacts, operation and maintenance, anticipated persistence of savings, etc. Use life-cycle costing, such as savings-to-investment ratio on a net present value basis, accounting for the time value of money, as well as the projected inflation of fuel costs. These all account for costs and benefits in a more complete manner than simple payback. Summary A variety of structured techniques can help make energy audits in large commercial office buildings easier. • Analyze utility bills before doing the field visit. Disaggregate use by season, fuel, building, and meter. Look for anomalies in energy use patterns to guide the search for unusual energy loads and savings opportunities. • Assign two people for the site visit, each with a walkietalkie or cell phone. An effective combination of staff can be an engineer familiar with HVAC plant and controls and an energy technician familiar with lighting, envelope, and plug loads. • Look for incorrectly operating HVAC systems, such as programmable setpoints that have not been correctly set (reset controls for hot and cold water temperatures, space temperatures, ventilation schedules, etc.). • Come prepared with a data collection plan, including data sheets. • Schedule adequate time for fieldwork. One day is inadequate for an effective site visit for a large commercial office building, even for a two-person team. • Bring a small set of useful tools, most of which fit in a small tool bag or even on a belt: infrared thermometer, CO2 meter, tape measure, reduced scale plans, light meter, lighting ballast checker. • Involve building staff; ask probing questions about schedules, controls, and suspected energy inefficiencies and savings opportunities. • After the site visit, immediately write a detailed building January 2009 Large commercial office buildings present a variety of challenges that are specific to the sector. An incremental approach (walkthrough audit first) runs a significant risk of not leading to significant or measurable energy savings. The higher cost of comprehensive audits is well justified by the greater energy savings opportunities identified and by avoiding duplication of effort, as many improvement descriptions, which guide implementation can be provided in the audit. A comprehensive approach using structured techniques can make the work easier and provide a framework for substantial and measurable energy savings. References 1. Energy Information Administration, Office of Energy Markets and End Use. Forms EIA-871A, C, and E of the 2003 Commercial Buildings Energy Consumption Survey. 2. Mazzucchi, R.P. 1992. “A guide for analyzing and reporting building characteristics and energy use in commercial buildings.” ASHRAE Transactions 98( 1):1067 – 80. 3. Ganji, A.R. 2002. “Investment grade energy audit.” 25th World Energy Engineering Congress. 4. 2003 ASHRAE Handbook—HVAC Applications, Chapter 35, Energy Use and Management, p. 35.14. 5. Office Energy Audit and Follow-up Analysis, Ithaca, N.Y. 2008. 6. Residential Energy Services Network. 2008. National Standard for Home Energy Audits. 7. ANSI/ASHRAE/IESNA Standard 90.1-2004, Energy Standard for Buildings Except Lo w-Rise Residential Buildings, Tables 9.5.1 and 9.5.2. 8. Office Energy Audit, Lansing, N.Y. 2006. Acknowledgments This work was supported by the Taitem Engineering C-NEW Applied Energy Research Initiative. Susan Galbraith and Dan Clark contributed to development of many of the lighting energy audit techniques described in the article. ASHRAE Journal 27
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