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Part 1: Higher Energy Star Score Key to LEED-EBOM
By Jenny Carney
May 2012 -
Green Article Use Policy
Energy efficiency in general, and the Energy Star score specifically, have long been key pieces of the LEED-EBOM rating system. In an ideal world, if a building owner is interested in LEED-EBOM and comes in with a low Energy Star rating, the next step would simply be to perform an energy audit and start working towards savings through capital and operational measures.
Unfortunately, the more common reaction seems first to suspect a problem with the Energy Star algorithm or data inputs, and next to abandon thoughts of LEED. It's only the projects within close striking distance of the minimum Energy Star score that seem to work out a strategic plan to save energy and elevate their score.
As a general rule of thumb, if you have a score under 50, it will take capital investments to raise the score sufficiently to achieve a LEED certification (or an Energy Star label, though, it should be noted that you don't need an official Energy Star label to get LEED-EBOM certification). Between 50 and 75, low-cost and operational measures may be enough.
Whatever your score, if LEED is in your plans, it's important to first concentrate on raising your score in incremental steps. If you have a low score, don't expect that LEED certification will happen overnight. But it can happen. Follow these steps to staged energy efficiency gains, with an eye on the LEED certification prize down the road.
As a bit of background, when the U.S. Green Building Council (USGBC) launched LEED for Existing Buildings (LEED-EB) v2.0 in 2005, the minimum Energy Star score required to achieve the Minimum Energy Efficiency prerequisite was 60. Under the current version (v2009), it is 69, and the proposal for LEED v2012, which will be released this fall, sets the minimum at 75.
This 2012 proposal amounts to a 15 percentile point jump in the minimum score, and though it may be tempting to think of that as the same as a 15 percent increase in the required performance, that's not actually how Energy Star works. Some quick test scenarios indicate this is more like requiring an 18 percent reduction in consumption for an all-electric office building that was LEED-EB-eligible in 2005 just to stay eligible in 2012.
Of course, at the same time, changes to the underlying algorithms that drive Energy Star ratings or the foundation of data fueling them — primarily from the Department of Energy's Commercial Building Energy Consumption Survey (CBECS) — can also result in changes to Energy Star scores that are beyond facility managers' control.
For example, in early 2009 the algorithm for rating hotels was revised. For some properties, this meant a higher score overnight with no changes to the building or its energy consumption, and for others a score that went down. On average, more hotels saw their scores drop than rise.
So what do these changes to LEED and changes to Energy Star mean in terms of how much more difficult it will be to qualify for LEED in 2012 versus 2005? If the CBECS database changes again, how will that affect projects with LEED certification goals? And what's the corresponding change to site or source energy use intensity (EUI) that a facility manager will have to achieve? At this point, the answers to these questions are anyone's guess.
A complicating factor can be that there is no straightforward way to understand how a building's Energy Star score will change with decreases in annual kBtu/sf. If the building's occupancy, occupied hours, number of computers, or the Energy Star program itself change during the same timeframe as energy reductions, it will impact the rating in a way that is not predictable or understandable to the typical user. Such uncertainty by itself is not a compelling case for large-scale and expensive investments (though, of course, energy saving itself is). When building owners pour money at a problem, they (understandably) want reasonable certainty about the results. For these reasons, it's far easier to set and work towards annual kBtu/sf targets than towards a specific Energy Star rating.
Green Building Report
Part 2: Auditing, Retrocommissioning Can Lead to Better Energy Star Score, LEED Success
Part 3: LEED-EBOM's Energy Star Prerequisite Not Intended to Discourage Participation
Part 4: USGBC Perspective: LEED 2012 On Its Way