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.
A 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.
Retro-commissioning of four Morgan Stanley buildings in New York, managed by Houston-based Hines Property Management, provides an example of how the process works. The project began with the selection of commissioning team members for each building comprised of Hines building engineers and the retro-commissioning agent, Old Saybrook, Conn.-based Strategic Building Solutions. An energy audit was done in conjunction with the retro-commissioning process.
During the discovery phase, the team reviewed building operating procedures, documentation and drawings along with the original design intent of the building, explains Dan Pugliese, director of engineering at New York-based Morgan Stanley. The reviews identified over 150 energy conservation measures, or ECMs. Each ECM was listed in a matrix showing the implementation cost and return on investment.
ECMs with paybacks under two years were implemented. They range from simple operation strategies which required no capital expenditures to fan upgrades and other retrofits, Pugliese says. The measurement and verification phase, now in process, is determining if the projects reaped the intended return on investment and expected energy savings.
NYSERDA, the New York State Energy Research and Development Authority, provided funding for the work under a building performance project opportunity notice (PON) that paid for the retro-commissioning study and offered performance incentives for energy reductions. The project also took advantage of NYSERDA’s FlexTech program that offers a 50/50 cost share for technical assistance.To date the facilities have reduced electricity usage by 21 percent and fossil fuel consumption by 26 percent. Expected saving are $2.4 million annually. Given the success of the project, the firm is now considering implementation of ECMs with paybacks of 3.7 years or less, Pugliese says.