Some buildings in urban areas may have high water and sewer utility rates that make water conservation a particular point of emphasis, but in most cases the lions share of operational cost savings will come from improving energy performance over time. With LEED O+M, understanding energy audits and retrocommissioning (existing building commissioning) and the difference between them can help you achieve your energy conservation goals.
Energy audits are best for older buildings, which need modernizing capital upgrades. Use the energy audit process to identify and triage energy conservation measures to bring your facility up to speed and create a budget and schedule for capital improvements. An ASHRAE Level I walkthrough is good for getting your feet wet in the energy audit process and can help identify some of the obvious low-hanging fruit, like lighting upgrades, for instance. But ultimately, a more comprehensive ASHRAE Level II energy survey and analysis will provide you the detail, including anticipated first costs and payback periods, that you will need to make informed decisions about if and when to implement capital improvements of your buildings systems.
Existing building commissioning is best for newer buildings that have the modern controls that allow a qualified retrocommissioning professional to, essentially, tune up a facilitys systems to optimize their performance. According to a 2009 study by Lawrence Berkeley National Laboratory, for an average of $0.30/sf in first cost, retrocommissioning reduces median energy consumption by 16 percent with a payback period of 1.1 years. Heres the simplest rule of thumb in deciding whether to perform an energy audit or retrocommissioning for your facility: A project with older pneumatic controls probably should use the energy audit approach, whereas buildings with modern controls should undergo retrocommissioning.
For LEED O+M version 4, buildings must achieve at least a 75 (increased from 69 in LEED 2009) on the Energy Star scale thats a prerequisite. If buildings cant achieve 75, they must demonstrate a 25 percent reduction in energy use from a stated baseline. But in the latter case, a building can only achieve the Certified level of certification. In LEED O+M version 4, buildings also must implement building-level energy metering to be eligible for any level of certification.
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