New NYC Buildings Less Efficient

Large buildings constructed in New York City since 1935 are by today’s standards less energy efficient.

Reading this article from Metropolis Mag on what’s wrong with green architecture, and LEED certification in particular, I noticed references to New York City measuring energy efficiency for some famous buildings: the Chrysler Building, the new 7 World Trade Center, and the Seagram Building, amongst others. Drawing from a Times article, they observed that the newer buildings, even LEED certified ones, performed worse:

Among other reasons for this failing, the Times pointed to the widespread use of expansive curtain-wall glass assemblies and large, “deep-plan” designs that put most usable space far from exterior walls, forcing greater reliance on artificial light and ventilation systems.


The Times and Metropolis mag stuck to anecdotal evidence, not looking beyond a few buildings. Fortunately, the city put all the scores online.

So it’s easy to test: are buildings constructed since the advent of mid-century modern building techniques less energy efficient?

Of 4000 reports, about 1600 recorded an actual “Energy Star Score”,

ENERGY STAR Score: A 1-to-100 percentile ranking for specified building types, as calculated by Portfolio Manager, with 100 being the best score and 50 the median. It compares the energy performance of a building against the Commercial Buildings Energy Consumption Survey (CBECS), a national database, and independent industry surveys for that building type. This rating is normalized for weather and building attributes in order to obtain a measure of efficiency.


1600 ain’t a bad sample size. And what buildings are on the sheet?

…all privately-owned properties with individual buildings over 50,000 square feet or with multiple buildings with a combined square footage over 100,000 square feet…


Big office buildings.

The essential context, “When was this building built?” was missing. But there were BBLs, the NYC property identification number. Since the Department of Finance makes available BBL-indexed tax roll data with when buildings were built, all’s that had to be done was to download the tax roll, convert it from MS Access format (fun!) and join it to the environmental ratings.

Keeping the sample size respectable by looking in five-year-increments, the pattern is clear: large buildings constructed prior to 1935 do much better by today’s energy efficiency standards than those constructed after.

I’m making the environmental data joined to year built available as a CSV for anyone to play with. Below is a chart including sample sizes, for the statistically curious.