Strategically Green - Rooftop Thermal Solutions: A TIAA-CREF Experience
By: Todd Coulard, commercial real estate vertical market leader and Steve Wey, district general manager, New York/New Jersey region, Trane
The rooftop thermal storage solution at the TIAA-CREF headquarters in Manhattan is anticipated to save $765,000 annually in energy and operating costs. Photos courtesy of Jonathan Joyce, JVJ Productions.
The 578,000-square-foot TIAA-CREF headquarters building, located at 730 Third Avenue in midtown Manhattan, uses a combination of high-efficiency electric chilled water systems and a rooftop thermal storage system to save energy and operating costs.
In 2007, TIAA-CREF management began looking for ways to reduce costs and improve building performance. They knew that installing new, more efficient HVAC systems could help them save energy and operating costs, while also reducing the building’s environmental impact.
TIAA-CREF partnered with the Trane energy services group to conduct a comprehensive energy analysis which led to a number of recommendations, several of which were implemented. Targeted energy conservation measures included installing the high-efficiency chilled water and thermal storage systems, which are significantly more energy-efficient and environmentally responsible than the high-pressure steam equipment they replaced. The company also reprogrammed the building’s centralized automation system.
During off-peak hours, one of the electric chillers in the building runs at full load throughout the night to freeze water in the 30-tank, 6,000 ton-hour thermal storage system. This process reduces overall utility costs because off-peak electricity is less expensive. The stored cooling capacity is discharged during the day to reduce the building’s daytime peak electrical demand and on-peak electric consumption. By installing the system on the roof, TIAA-CREF did not have to give up any of the building’s premium leasable space. The project earned a $219,000 incentive from the New York State Energy Research and Development Authority (NYSERDA).
Based on Trane’s energy analysis, a chilled water system for ice production during off-peak hours and a 30-tank thermal storage system was selected, providing 6,000 ton hours of thermal storage.
The heating, ventilation and air conditioning (HVAC) system redesign delivered about $840,000 in savings per year in its first two years of operation. The project was originally projected to save between $765,000 and $840,000 per year in energy and operating costs. An independent analysis revealed that actual savings for 2009 and 2010 were at the high end of that range. TIAA-CREF reports that the project has demonstrated a 25 percent internal rate of return on the company’s investment. The retrofit is also expected to reduce the building’s carbon emissions by about 6.1 million pounds per year, which is equivalent to taking 560 cars off the road.