A Benchmarking Head-Scratcher: Is Older Better?

benchmarking
Patrick Hewlett for Zondits, March 31, 2015

New York City’s Local Law 87 reveals top performers and savings potential—and some surprises.

Introduced in 2009, New York City’s Local Law 87 (LL87) requires that all residential, commercial, and municipal buildings exceeding 50,000 square feet undergo an energy audit and retro-commissioning study every 10 years. This legislation not only refreshes the city’s largest buildings with current energy efficiency ideas and operating best practices, but also provides the city with rich benchmarking data to identify buildings with the highest energy savings potential. One such benchmarking data point is an ENERGY STAR performance index, in which a score of 75 (out of 100) earns the EPA’s high-efficiency buildings certification.

But the benchmarking index alone often does not tell the whole story. Consider the following two buildings for which benchmarking results were released in 2013:

  • Building A is a 6-year-old, LEED Gold-certified, high-rise office building.
  • Building B is a high-rise office building constructed in 1930.

So which received the higher benchmarking score? To the surprise of many, Building B outperformed Building A. Building B is the iconic Chrysler Building, while Building A is the more modern 7 World Trade Center. On paper, the octogenarian Chrysler Building could seem like a potential energy hog, but its extensive envelope and HVAC retrofits have modernized its systems to outperform its newer peers.

Another variable to consider when comparing large New York buildings is tenants. 7 World Trade Center leases to several international financial consultants and IT firms with in-house data centers; the plug loads of such businesses can far exceed those of a traditional nine-to-five companies. But auxiliary equipment like plug loads can be difficult to consistently characterize with standard benchmarking forms.

LL87’s benchmarking effort produces extensive building performance data, but careful planning and quality control are needed to ensure that the data is accurate. Nearly 25% of all benchmarking data from the LL87’s first year was scrubbed due to inaccuracies or inconsistencies among facilities. To mitigate these errors, the nearby Center for Building Knowledge at the New Jersey Institute of Technology (NJIT) launched a Certificate of Proficiency in Benchmarking training on accurately collecting relevant energy and water usage data. Another idea is piloting: aggregating and analyzing the results from a pilot set of buildings can highlight systemic errors before the majority of buildings are visited.

With more training options and careful piloting, future benchmarking efforts will see greater levels of accuracy and consistency, leading to fewer head-scratchers.

1 comments

Building B may have received a better score because of the flawed system using “source” estimates. Building B may be using fuel oil with no emission controls for space heating and water heating, and Building A may be using very high efficiency heat pumps, but because of inaccurate “source” estimates, Building B looks better under this flawed methodology. Also, since fuel oil and propane are not typically metered, some building owners may “forget” to enter data for their consumption.

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