The City of Chicago recently issued its annual report on commercial building benchmarking. I pick on Chicago because (1) its upper-Midwest location has a climate like that of many of our readers, and (2) because it uses ENERGY STAR® Portfolio Manager, which I addressed several times before. With Portfolio Manager, everybody seems to get a trophy, and results are troublesome to me.
Also, for reference, I published this post last fall, pointing out the failures of energy codes to move the energy intensity needle. Using data from the Energy Information Administration, that post showed that buildings built in the past three decades consume more energy than older buildings, per square foot.
Chicago Benchmarking Statute
Chicago’s statute requires commercial, institutional, and multifamily properties of 50,000 square feet and greater to report energy consumption, square footage, other characteristics, and enter the data into ENERGY STAR Portfolio Manager. Chicago’s report indicates the qualifying building count is 3,538, and the city achieved 80% reporting compliance.
Results and Analysis
The chart to the left is a bit busy, but it shows the vast majority of Chicago’s building stock is less than 50 years old, and that construction from the 1960s through the first decade of the 2000s was cheap and crappy. The ENERGY STAR scores are lowest in this range of construction. I would surmise the reason for this is that the old buildings built in the 1920s-30s are massive. Like the building we occupy in La Crosse (circa 1910), these massive buildings, to some extent, resemble living in caves, but with nice daylighting. Take a stroll along Michigan Avenue down by Grant Park sometime and observe the incredibly massive structures in these old buildings.
ENERGY STAR Portfolio Manager Flaws
Last week I explained the virtues of ENERGY STAR standards for consumer and small commercial products. The EPA needs to reconnoiter its scoring model for Portfolio Manager. How can office buildings score an average of about 75 while healthcare and lodging average only the upper 30s? The score is supposed to be relative to similar buildings in similar climates. Are Chicagoland architects, engineers, and builders that much better at building efficiency into office buildings? No. Way.
Furthermore, the report provides the following data for buildings that were reported to the program for three years versus those reporting for two years. That is not a typo, at least on my end. Half the energy savings (1.9%) result in a greater increase in Portfolio Manager score. How does that calculus work?
I imagine there are too many variables in the Portfolio Manager soup and they are inappropriately weighted. I would also question how it scores an electric Btu versus fossil (natural gas) Btu, and source Btu versus site Btu. These are forever confusing and misleading. Why? Because using Btu for electricity makes no sense whatsoever.
The Ill-Advised Use of Electrical Btu
A British thermal unit (Btu) is the amount of thermal energy required to raise the temperature of one pound of water (or a pint of beer), one degree Fahrenheit. One kilowatt-hour produces roughly 3,413 Btu; enough to boil away and perfectly ruin about one pint of beer on a conventional electric stove.
The energy required to produce the kWh varies from zero (wind and solar) to maybe 6,000 for combined cycle natural gas, to maybe 12,000 for coal or nukular, and even more for natural gas peaker plants. See where this is going? The great unknown – that’s where. It becomes very difficult to reverse engineer what Portfolio Manager is doing for this stuff.
The right way to benchmark is to separate electric from site-burned fossil (natural gas, fuel oil, propane), and use an equivalent kWh or site Btu amount for other supplied utilities like chilled water and steam.
For example, if a customer is on a downtown district chilled water plant (like Chicago has), determine how many kWh a typical chilled water plant would need to produce that chilled water, and add it to the building’s kWh for benchmarking. Similarly, determine the probable natural gas consumption required to produce the steam purchased. This is how to compare these buildings against larger populations.
Come to think of it, this may be the source of another flaw in Portfolio Manager. How does it handle district chilled water and steam consumption? I don’t know, and it isn’t worth my time because in real life, the only thing that matters is how much a customer is paying for energy used. And that most accurately shakes out when electric and fossil fuels are separated as described.
The simple view is this: the value of electric Btu to gas Btu is about 5:1. Any mixing of the two ruins the benchmarking effort.
Weed Growers Discover Sun
A year ago, I gave energy advice to cannabis growers in Cannabis – A Big Issue Coming To a Utility Near You. During the course of researching for that blog, I asked, “What is wrong with the sun, fresh air, and native soil for this crop?” Apparently, pot growers have cracked the code and have taken their operations outdoors, averting rolling blackout crises.
 Energy use per square foot.
 Not related to Chicago benchmarking