With new legislation passed in New York City late last year, all of New York's buildings totaling more than 50,000 sq ft are required to submit to benchmarking and retro-commissioning, essentially putting those buildings' efficiency ratings up against other buildings across the country.
Benchmarking essentially ranks a building’s energy and water efficiency against similar buildings. The legislation specifies the use of the U.S. EPA’s Portfolio Benchmarking tool as the standard for calculating the ranking.
The process is very simple. Data on a building’s energy consumption and energy costs are input into the tool. “By entering seven or eight variables you can benchmark an office building in about five minutes,” says Richard Tesoriero, senior mechanical engineer, Steven Winter Associates, Norwalk, Conn.
The tool is comprised of statistically representative models that compare a building against similar buildings from a national survey, known as the Commercial Building Energy Consumption Survey (CBECS). The survey gathers data on building characteristics and energy use from thousands of buildings across the United States every four years.
The model calculates energy usage per square foot and provides a percentile ranking from 1 to 100 of the building’s energy performance relative to similar buildings. A rating of 60 indicates that from an energy consumption standpoint the building performs better than 60 percent of all similar buildings.
“If you are above the 75th percentile you are in a position to get some recognition through an Energy Star plaque or by pursuing a certification like LEED for Existing Buildings,” Tesoriero explains.
Retro-commissioningA retro-commissioning process investigates how a building is maintained and operated in order to identify ways to optimize building performance as well as increase energy efficiency and reduce operating costs.