ASHRAE Journal - January 2009 - (Page 26) The comprehensive energy audit idenWalkthrough Comprehensive tified savings of 46%. Interestingly, the Audit Audit predicted energy savings appear to have Percent Savings 7% 46% been exceeded by those improvements, Room-by-Room No Yes which were implemented by the owner. Number of Improvements 8 12 Natural gas savings were measured at 53%, following replacement of the boilLighting Improvements No Yes ers, window replacement, installation of HVAC Plant Improvements No Yes summer boilers for service hot water, HVAC Consolidation/Reduction No Yes and separation of the heating plant into Controls Improvements Yes Yes multiple zones.5 Health/Safety/Comfort Improvements No Yes Meanwhile, the walkthrough audit in a HVAC Distribution Improvements No Yes different large commercial office building identified savings of only 7%. Sometimes Demand/Purchasing Recommendations Yes Yes presented as a preliminary audit, or a No Yes Motor Improvements precursor to an in-depth audit, the walkO&M Recommendations No Yes through audit runs the risks of delivering Service Hot Water Improvements Yes Yes small savings, satisfying the owner’s need Tenant Education Recommendations No Yes to make energy improvements, allowing Envelope (Insulation, Air Sealing) Improvements Yes Yes “greenwashing” claims, giving the false impression that significant savings are Plug Load Improvements No No not possible, preventing the owner from Table 3: Comparison of two example commercial ofἀce energy audits. considering comprehensive work, and deferring in-depth improvements for years into the future. Missed Energy Further risks derive from the possibility that energy savings Measures estimated in an energy audit can easily be eroded between the Reduced Project Scope Installation energy audit and final implementation. These risks are illustratDeficiencies ed in Figure 1. Beyond the risk of energy savings not materialOperation and izing because the audit itself is not clear or because the auditor Maintenance missed energy measures, there is the risk of the owner choosing not to implement all the savings, the risk of contractors makPotential Savings ing mistakes or substituting less efficient products, the risk of inadequate commissioning of energy conservation installations, Delivered Savings and the risks of poor operation and maintenance. All of these can erode the originally recommended savings. Comprehensiveness is the best hedge against the erosion of these savings between Figure 1: Erosion of energy savings. energy audit and closeout of implementation. Finally, projected savings as small as 7% present a high risk of actual savings not being measurable, as real savings are lost appliances (replace an oversized ice-maker, intelligent power control on vending machines). in the “noise” of fluctuating energy use in a building. Projected annual savings are $125,000 per year, or 37%. Case Study The cost of the audit was approximately $27,000. The ratio of A different example points to audit costs and projected estimated audit cost to annual energy costs savings is 0.22. In savings of a comprehensive audit.8 A 77,000 ft2 (7154 m2) other words, the energy savings will pay for the audit in 0.22 office building in upstate New York has annual electricity years, or approximately 2.6 months. costs of $130,000, and annual gas costs of $210,000, for The final report provides a variety of detail that may be helpful total annual fuel costs of $340,000. A comprehensive energy for the owner in proceeding with implementation, including inforaudit identified 14 improvements, all of which meet a posi- mation on all 32 motors to be replaced (location, load description, tive life-cycle cost test (savings-to-investment ratio greater horsepower, quantity, existing efficiency, recommended minimum than one). The recommended improvements include HVAC replacement efficiency, etc.), 20 pages of lighting data with roomplant (new high-efficiency boilers), HVAC distribution (new specific recommendations, and more. Much of the scope of work VAV system, premium efficiency motors, pipe insulation), for implementation is already defined in the energy audit. HVAC controls, ventilation (new energy recovery ventilation We estimate that the cost of a walkthrough audit might be system), envelope (door weather stripping, storm windows), $5,000 and provide 7% annual savings, as shown in the prior lighting (extensive delamping, relamping, and controls), and example, or approximately $24,000 energy cost savings per 26 ASHRAE Journal ashrae.org January 2009 http://www.ashrae.org
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