Tag Archives: energy benchmarking

Energy Star Scores for LEED EBOM Offices

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This is my first post in over a year. As with most of us, covid-19 has changed my priorities.

For some time now I have been studying the energy performance of LEED buildings using Municipal building energy benchmarking data.  I have also investigated the science that underpins the EPA’s building Energy Star score.  In our most recent study, these two issues intersect.

We have completed the largest study of measured energy performance of LEED-certified buildings.  The sources of our data are publicly-reported building energy data from ten cities: Boston, Chicago, Denver, Los Angeles, Minneapolis, NYC, Philadelphia, Portland, Seattle, and Washington DC.  In total we have 2016 energy data from 28,480 properties (buildings or groups of buildings) in these 10 cities.  In these data we have identified about 850 LEED-certified commercial buildings.  This has allowed us to compare the 2016 energy use of LEED buildings with those of similar buildings in the same city for the same year.

Here I want to talk about just one aspect of this study – the 2016 Energy Star scores for offices that were certified under LEED EB:OM (Existing Buildings: Operation & Maintenance).  Offices certified under a LEED EB:OM system are awarded LEED points for energy optimization based on the Energy Star score they earn during a year of operation.  This score (EAc1) can be found for many of these buildings on the Green Building Information Gateway web site.  And this score can be used to determine the Energy Star score that was reported to the USGBC used to earn this score.

Now if a building earned an Energy Star score of 85 at the time of LEED certification, you would expect it to continue earning a similar high score for subsequent years of operation.  We have compared this “Design Energy Star score” (i.e., the score that was used in awarding EAc1 points) with the Energy Star score reported in 2016 municipal benchmarking data for nearly 450 LEED certified offices in these 10 cities.  The graph below shows this comparison.  The color code indicates the LEED system used for certification.

The graph shows there is surprisingly little correlation between these two Energy Star scores.  The purple dashed line represents y = x, the expected result if the 2016 Energy Star score earned by the building is the same as that submitted for certification.  The solid black line is the actual trend line obtained by fitting a straight line to the data.

What we see is that only 19% of the variation in 2016 Energy Star scores is “explained” by the score submitted at time of certification.  81% of the variations in 2016 Scores is unrelated to this initial score.  The pink rectangle shows the range of 2016 Energy Star scores for offices that earned a score of 85 at time of certification.  There are 35 such buildings, and their 2016 Energy Star scores range from 60 to 99.  You see similar variation everywhere along the curve.  In the most outrageous cases a building’s Energy Star score in 2016 was 52 points lower than what was reported when it was LEED certified!

It is very doubtful that these changes in Energy Star score reflect real changes in the energy consumption and operation of these offices.  A much more likely explanation is that the operating parameters reported in securing these scores have changed – not reflecting real changes in computer density, or worker density, or operating hours, but just arbitrary changes due to the fact that a different person (with different motivations) reported these numbers in 2016 from the person who reported them at time of certification. The data illustrate the arbitrary nature of the Energy Star score and the ability to significantly change the score by just submitting different operating parameters.  There is no regulation of these submittals – you can change the number of computers in the building from 4000 to 8000 and there is no one who will question the number.  And this will dramatically change your Energy Star score.

In the past the EPA’s Group that works on Energy Star scores has had exclusive access to the data they gather. But with cities publishing these scores we now have the ability to check them and to see their patterns. The mean and median Energy Star score for the 4200+ offices in the benchmarking data are 74 and 80, respectively.  The EPA claims that the median Energy Star score is 50.  This is nonsense.  These 4200+ offices constitute a sizable fraction of the U.S. office space.  Like the children of Garrison Keillor’s mythical Lake Wobegon, all urban buildings are above average.

DC Benchmarking data show modest energy savings for LEED buildings

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A few months ago Washington DC released its 2012 energy benchmarking data for private commercial buildings 150,000 sf and larger.  Credible energy and water consumption data for some 400 buildings were released, of which 246 were office buildings.  A recent article — stemming from the web site LEED Exposed — has claimed that these data show LEED buildings use more energy than non-LEED buildings.  Specifically it is claimed that LEED buildings have an average weather normalized source EUI of 205 kBtu/sf whereas non-LEED buildings have an average EUI of 199 kBtu/sf.   No details are provided to support this claim.

My students and I have cross-listed the DC benchmarking data with the USGBC LEED Project directory and identified 94 LEED-certified buildings in the 2012 DC benchmarking dataset — all but one being classified as office buildings.  The unweighted mean weather normalized source EUI for these 94 LEED certified buildings is 202 kBtu/sf.   The unweighted mean weather normalized source EUI for remaining 305 buildings is 198 kBtu/sf.  No doubt this is the basis for the claim that LEED buildings use more energy than non-LEED.  However, the difference is not statistically significant.

Moreover, the non-LEED dataset, in addition to 154 office buildings, contains 64 (unrefrigerated) warehouses and 90 multifamily housing buildings — all of which use significantly less energy than do office buildings.  The comparison of these two average EUI is not useful — just a meaningless sound bite.

It should also be noted that the unweighted mean EUI for a collection of buildings is an inappropriate measure of their total energy consumption.  The appropriate measure of energy consumption is their gross energy intensity — their total source energy divided by the total gross square footage.  This issue has been discussed in several papers [2008 IEPEC; 2009 Energy & Buildings].

Note that an apples-to-apples comparison of energy consumed by one set of buildings to that consumed by another requires that the two sets contain the same kinds of buildings in similar proportions.  When possible this is best accomplished by sticking to one specific building type. Since office buildings are far and away the most common in both datasets it makes sense to make an office-to-office comparison — pun intended. 

93 of the LEED-certified buildings are offices.  But many of these buildings were not certified during the period for which data were collected.  Some were certified during 2012 and others were not certified until 2013 or 2014.  Only 46 of the office buildings were certified before Jan. 1, 2012 and are then expected to demonstrate energy and GHG emissions savings for 2012.

The 2012 gross weather-normalized source energy intensity for the 46 LEED certified office buildings is 191 kBtu/sf.  This is 16% lower than the gross weather-normalized source energy intensity for the 154 non-certified office buildings in the dataset, 229 kBtu/sf.  These modest savings are real and statistically significant, though much lower than the 30-40% savings routinely claimed by the USGBC.

Note that similar savings were not found in 2011 or 2012 NYC energy benchmarking data. Analysis of these data showed that LEED-certified office buildings in NYC used the same amount of primary energy and emitted no less green house gases than did other large NYC office buildings.  So the 2012 results from Washington DC are significantly different.  It should be noted that NYC office buildings certified at the gold level were found to exhibit similar modest energy savings.  Perhaps this is a clue as to why Washington DC LEED buildings show energy savings.  More analysis is required.

For the last few years the USGBC has pointed to ENERGY STAR scores for LEED certified buildings as evidence of their energy efficiency.  While ENERGY STAR scores have two important characteristics — they use source rather than site energy and they are based on actual energy measurements — they simply do not have sound scientific basis.  The science has never been vetted, and my own analysis shows these scores are little more than placebos to encourage energy efficiency.  They certainly do not have any quantitative value.

So to summarize, in 2012 LEED offices in Washington used 16% less source energy than  did other office buildings in DC.  What this means and whether such savings justify the added costs of LEED are open questions.

USGBC Continues to “cherry pick” LEED energy data

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At the 2007 GreenBuild Conference the USGBC released the results of their first major study of energy consumption by LEED-certified buildings.  Then they presented conclusions from the now infamous study conducted by the New Buildings Institute (paid for by the USGBC and EPA) which, based on data “volunteered by willing building owners” for only 22% of the eligible buildings certified under LEED NC v.2, concluded that LEED certified buildings, on average, were demonstrating the anticipated 25-30% savings in (site) energy.

NBI’s analysis and conclusions were subsequently discredited in the popular media by Henry Gifford and in the peer-reviewed literature by me [see IEPEC 2008 and Energy & Buildings 2009].  NBI’s analytical errors included:

  1. comparing the median of one energy distribution to the mean of another;
  2. comparing energy used by a medium energy subset of LEED buildings with that used by all US commercial buildings (which included types of buildings removed from the LEED set);
  3. improper calculation of the mean (site) energy intensity for LEED buildings and comparing this with the gross mean energy intensity from CBECS;
  4. NBI looked only at building energy used on site (i.e., site EUI) rather than on- and off-site energy use (i.e., source EUI).

To NBI’s credit they made their summary data available to others for independent analysis with no “strings attached.”  In the end even the data gathered by NBI, skewed towards the “better performing” LEED buildings by the method for gathering data, when properly analyzed demonstrated no source energy savings by LEED buildings.  LEED office buildings demonstrated site energy savings of 15-17% — about half that claimed by NBI, the difference being associated with NBI’s improper averaging method.  This site energy savings did not translate into a source energy savings because LEED buildings, on average,  used relatively more electric energy, and the off-site losses associated with this increased electric use wiped out the on-site energy savings.

The lack of representative building energy data was addressed in LEED v.3 (2009) by instituting a requirement that all LEED certified buildings supply the USGBC with annual energy consumption data for five years following certification.  Never again would the USGBC have to publish conclusions based on data volunteered by 1 in 5 buildings.  Expectations were high.

But what has this produced?  The USGBC has learned from their experience with NBI — not to hand over such an important task to an outside organization because you can’t control the outcome.  NBI’s analysis was scientifically flawed — but it was transparent, and such transparency gave critics ammunition to reach different conclusions.  Nowadays the USGBC simply issues carefully packaged sound bites without supplying any details to support their conclusions.  There isn’t even a pretense of conducting scientifically valid analysis.

Consider the most recent claims made by the USGBC at the 2013 Greenbuild conference, summarized by Tristan Roberts in “LEED buildings above average in latest energy data release.”  Roberts asserts the following:

  1. The USGBC has received energy data from 1,861 certified buildings for the 12-mos period July 2012 – June 2013;
  2. About 70% of these were certified through LEED-EBOM (existing buildings);
  3. 450 of these buildings reported their data through the EPA’s Portfolio Manager;
  4. the “building-weighted” (or un-weighted) average source EUI for these 450 buildings is 158 kBtu/sf;
  5. this average is 31% lower than the national median source EUI;
  6. 404 (of the 450) buildings above were eligible for (and received) ENERGY STAR scores;
  7. the average ENERGY STAR score for these 404 buildings was 85.

In addressing the above claims it is hard to know where to begin.  Let’s start with the fact that the USGBC only provides energy information for 450 (or 24%) of the 1,861 buildings for which it has gathered data.  Is this simply due to the fact that it is easier to summarize data gathered by Portfolio Manager than data collected manually?  If so I willingly volunteer my services to go through the data from all 1,861 buildings so that we can get a full picture of LEED building energy performance — not just a snapshot of 24% of the buildings which “self-select themselves” to benchmark through Portfolio Manager.  (The EPA has previously asserted that buildings that benchmark through Portfolio manager tend to be skewed towards “better performing” buildings and are not a random snapshot of commercial buildings.)

Next, consider the “un-weighted” source EUI figure for the 450 buildings.  This is a useless metric.  All EUI reported by CBECS for sets of buildings are “gross energy intensities” equivalent to the gsf-weighted mean EUI (not the un-weighted or building-weighted mean EUI).  This was a major source of error in the 2008 NBI report — leading NBI to incorrectly calculate a 25-30% site energy savings rather than the actual 15-17% site energy savings achieved by that set of LEED buildings.

Consider the assertion that the 158 kBtu/sf source EUI figure is 31% lower than the median source EUI (presumably for all US commercial buildings).  To be correct this would require the median source EUI for all US commercial buildings be 229 kBtu/sf.  This is rubbish.  The best way to obtain such a median EUI figure is from the 2003 CBECS data.  The Energy Information Administration (EIA) does not report source energy figures in any of its CBECS reports.  But the EIA does report site and primary electric energy used by buildings, and these may be combined to calculate source EUI for all 2003 CBECS sampled buildings.  This results in a median source EUI for the estimated 4.9 million commercial buildings to be 118 kBtu/sf.  If you instead restrict this calculation to all buildings with non-zero energy consumption you find these estimated 4.6 million buildings have a median source EUI of 127 kBtu/sf — way below the 229 kBtu/sf figure asserted by the USGBC.  This USGBC claim is patently false.  Of course the USGBC may be referring to the median source EUI of some unspecified subset of U.S. buildings.  By choosing an arbitrary subset you can justify any claim.  And if you don’t specify the subset — well, the claim is nothing more than noise.

What about the average ENERGY STAR score of 85?  Is this impressive?  The answer is no.  Even if you believed that ENERGY STAR scores were, themselves, meaningful, such an average would still mean nothing.  ENERGY STAR scores are supposed to represent percentile rankings in the U.S. building population.  Since there are 4.8 million buildings, by definition we would expect 10% of these (or 480,000) to rank in the top 10% and we would expect another 480,000 of these to rank in the bottom 10%.  That means that if 1,861 buildings are chosen at random from the building population, we expect 10% of these to have ENERGY STAR scores from 91-100.  Similarly, we expect 30% of these (or 558) to have ENERGY STAR scores ranging from 71-100.  Guess what — the average ENERGY STAR scores of these 558 buildings is expected to be 85.  Only those who are mathematically challenged should be impressed that the USGBC has found 404 buildings in its set of 1,861 that have an average ENERGY STAR score of 85.  If you cherry pick your data you can demonstrate any conclusion you like.

And, of course, these 1,861 buildings are not chosen at random — they represent buildings whose owners have a demonstrated interest in energy efficiency apart from LEED.  I would guess that the vast majority of the 404 buildings were certified under the EBOM program and have used Portfolio Manager to benchmark their buildings long before they ever registered for LEED.  LEED certification is just another trophy to be added to their portfolio.  No doubt their ENERGY STAR scores in previous years were much higher than 50 already.  What was the value added by LEED?

I openly offer my services to analyze the USGBC energy data in an unbiased way to accurately asses the collective site and source energy savings by these LEED buildings.  How about it Brendan Owens (VP of technical development for USGBC) — do you have enough confidence in your data to take the challenge?  Which is more important to you, protecting the LEED brand or scientific truth?

ENERGY STAR energy benchmarking is not ready for prime time

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I recently had occasion to read an old paper by Janda and Brodsky describing the “first class” of ENERGY STAR certified office buildings.  This is one of only a handful of papers in the peer-reviewed literature regarding ENERGY STAR building scores.  Janda and Brodsky describe the brand name ENERGY STAR as

a set of voluntary partnerships between the U.S. government and product manufacturers, local utilities, home builders, retailers, and businesses.  These partnerships are designed to encourage energy efficiency in products, appliances, homes, offices, and other buildings.

This was the basis for the EPA’s building ENERGY STAR scoring system.  It was a “game” that building managers voluntarily agreed to play with rules (methodology for scoring buildings) set by the EPA in consultation with those playing the game.  There was no scientific vetting of the “rules of the game” — nor did there need to be — it was just a game designed to “encourage energy efficiency.”  No one was forced to play the game.  Data submitted to Portfolio Manager (the EPA’s web-based tool for calculating scores) and ENERGY STAR scores issued by the EPA were confidential — unless a building sought and received ENERGY STAR certification.  Participation was entirely voluntary.  Building managers disappointed with their ENERGY STAR scores could just walk away from the game — no harm, no foul.

But this has all changed.  In recent years 1) the EPA has published specific claims regarding energy savings associated with its ENERGY STAR benchmarking program (real savings not just fantasy football), 2) external organizations like the USGBC have adopted the ENERGY STAR score as their metric for energy efficiency in green building certification programs and are using these scores to make energy savings claims of their own, and 3) major U.S. cities have passed laws requiring commercial building owners to use Portfolio Manager to benchmark their buildings and, in many cases, the resulting ENERGY STAR scores are being made public.  With federal, state, and local governments requiring LEED certification for public buildings this is no longer a voluntary game — it is mandatory and real (testable) energy claims are being made based upon ENERGY STAR scores.  Now the science behind such claims actually matters — and this science has never been vetted.

Its kinda like a small, “mom and pop” operation that has been selling chicken soup using “grandma’s recipe” without obtaining proper license or FDA approval.  Now imagine Walmart decides to market and sell the soup — the scrutiny changes.

As a voluntary game with no connection to reality it is OK that the EPA negotiates rules for its ENERGY STAR ratings with different constituents — like allowing Washington DC office buildings to ignore their “first floors” in seeking ENERGY STAR certification.  After all, who am I to interfere in the activities between consenting adults when these activities do not affect me?  But for ENERGY STAR — these days are gone.

In the next year we will learn much about the science that underpins the EPA’s ENERGY STAR benchmarking system — and the results are likely to be very disappointing.  This benchmarking system is not ready for prime time.

NYC Energy Benchmarking raises questions about LEED-certification

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With growing concern over global climate change and the US Federal government frozen in political gridlock a number of U.S. cities have decided to unilaterally take action to reduce their own green house gas (GHG) emission.  Any serious effort to reduce GHG emission must involve the implementation of some kind of system to track energy consumption.  To this end these same cities have instituted Energy Benchmarking laws — laws that require building owners to annually submit energy consumption data (by fuel) to a designated agency that collects and processes these data.  The Institute for Market Transformation (IMT) has been instrumental in coordinating this effort.

The requirement is typically phased in over a couple of years — starting with municipal buildings, followed by large commercial buildings, smaller commercial buildings, and finally residential buildings.  New York City, Philadelphia, Washington DC, San Francisco, Austin, and Seattle were the first to pass such ordinances.  Minneapolis, Chicago, and Boston have all taken steps to follow suit.

Public disclosure of energy data is an important component of many (but not all) of these local ordinances.  New York City (NYC) is further along than other cities and last October released 2011 energy benchmarking data for commercial buildings that were 50,000 sf or larger — excluding condominiums.  Public benchmarking data were released for more than 4,000 large commercial buildings in the NYC’s five boroughs.  NYC, like many of the other cities engaged in benchmarking, utilized the EPA’s ENERGY STAR Portfolio Manager for gathering and processing benchmarking data.  Data released included building address, building type, total gsf, site energy intensity, weather-normalized source energy intensity, water usage, and total GHG emission.

The NYC benchmarking data included data for more than 1,000 office buildings.  Some of these buildings are certified green buildings, so would be expected to use less energy and have less GHG emission than other NYC office buildings.  These green buildings are not identified in the NYC Benchmarking data, but many may be identified by searching other data bases – such as the US Green Building Council’s LEED project database or the EPA’s list of ENERGY STAR certified buildings.

A few dozen LEED-certified office buildings have been identified in the 2011 NYC Benchmarking database.  (The full peer-reviewed paper is to be published in Energy and Buildings.)  Of these, 21 were certified before 2011 by new construction (NC), existing buildings operation and maintenance (EB:O&M), or core and shell (CS) LEED programs which address whole building energy use.  These 21 buildings constitute 21.6 million gsf.  Their 2011 source energy consumption and GHG emission has been compared with those for the other NYC office buildings with rather surprising results.  The LEED-certified office buildings, collectively are responsible for 3% more source energy consumption and GHG emission than other large NYC office buildings (adjusted for total gsf, of course).  The graph below compares source energy intensity histograms for the two building sets.

Source LEED-21 vs NYC 953pos

The graph shows that the difference in the mean source energy intensities of the two building sets is not statistically meaningful.  In other words, the source energy consumption and green house emission of these LEED-certified office buildings is no different from that of other NYC office buildings — no more and no less.

As of a few months ago there were something like 8,300 buildings certified under one of the LEED programs that claim to reduce whole building energy use.  Measured energy consumption data have been published for 3% of these (now about 250).  While many of these LEED buildings surely save energy, many do not.  Collectively the evidence suggests, that LEED certification does not produce any significant reduction in primary energy use or GHG emission.

Why then does the Federal Government — and other governments (including NYC) — require new government buildings to be LEED certified?   The Federal Drug Administration (FDA) would never certify a medical drug with so little scientific evidence offered — let alone require its use.  The standards here are inverted — apparently the Federal Government believes convincing scientific data must be offered to demonstrate that LEED-certified buildings do not save energy before they will change their policy.