Referring to the Sears Tower, which is occasionally called the “Willis Tower,” a Chicago Tribune article from December said the following: “It’s not quite the same as its previous distinction — the world’s tallest skyscraper — but Chicago’s Willis Tower has captured a new title: the largest U.S. building to achieve the highest level of energy efficiency.” This is misleading on a couple of levels.
First, in defense of LEED, the rating system addresses many aspects of sustainability, not just “energy efficiency.”
Second, to criticize LEED, the rating system does not require a building to be carbon neutral—which should be our goal—nor does it require a building to actually be very energy efficient at all, because the rating system’s points can be obtained elsewhere.
In contrast, if the Sears Tower had met the Living Building Challenge, that would be something.
The best measure of energy efficiency is Energy Usage Intensity, or EUI, which measures a building’s energy usage per square foot per year. On this measure, how does the Sears Tower perform?
According to Toward Zero Carbon: The Chicago Central Area Decarbonization Plan, the Sears Tower had a pre-renovation EUI of 35 watts/sf (I assume per year) and the goal was 19 watts/sf. This translates to:
119 kBTU/sf/year pre-renovation
65 kBTU/sf/year goal
According to the EPA, the median U.S. office building has an EUI of 53 kBTU/sf/year. However, the Sears Tower is a skyscraper, in Chicago, which has a significant heating load, so 65 kBTU/sf/year is commendable, assuming the goal were met.
Now, the challenge is providing that 65 kBTU/sf/year without using fossil fuels….
Here is the Chicago Tribune article: link