The IDS Center, downtown's signature skyscraper since it was built in 1972, also was considered a glass-encased energy hog when fuel prices started to accelerate in the mid-1970s. Several owners over the years have worked to make the building more efficient.

Accesso Partners, which acquired the building for a record $253 million in 2013, plans to make it greener yet.

Accesso has hired the Center for Energy and Environment (CEE) in Minneapolis to study the building over four seasons and incrementally take steps that should cut steam and electricity consumption by at least 10 percent, the cost of which should be recaptured within three years, based on CEE's track record with commercial buildings.

And the IDS Center, into which would fit about 10 Target stores, is downtown's tallest building and the biggest CEE has ever tackled.

"Our goal in the building recommissioning program is to make what you have work better," said Mark Hancock, CEE's lead engineer and a 26-year veteran of the nonprofit business that has worked with utilities, business and government buildings since 1980. "We'll process millions of data points to understand what happens over an extended period of time. The end result will be low-cost to no-cost improvements to optimize existing equipment. Our scope also could include recommending the possible replacement of some equipment.''

IDS management hasn't been sitting on its hands until now.

The IDS Center in downtown Minneapolis was built in 1972.

In the past 25 years, building management has switched to more efficient lighting, cut electricity use with new "magnetic levitation" water chillers for air conditioning and halved in 2009 the 57-story building's water use with a new closed-loop cooling system in helping achieve "Energy Star" certification by the U.S. Environmental Protection Agency, said Deb Kolar, general manager of operations at the IDS.

Kolar said increasing energy productivity, saving money and maintaining comfort are beneficial to the Accesso and tenants.

CEE has been cited nationally and received grants from industry and government over the years for its shared research and hands-on experience in helping clients.

CEE, through its "existing building commissioning program" that covers the majority of its work, analyzes building operations, tunes up the ventilation and indoor air-quality systems, trains management staff and verifies energy savings. CEE was introduced to IDS Center staff by NRG Energy Center, the downtown provider of steam and chilled water.

Last year, CEE worked with the historic Hotel Ivy for several months and uncovered the potential for the Ivy to make improvements that would save up to $77,000 annually, with building improvements paying for themselves within three years. They included optimizing the building's chilled water system, using outside air to mitigate the need for chilling and incorporating energy-efficient lighting.

CEE over several months collected continuous data on all available mechanical equipment in the building, which includes lodging, restaurant, spa-fitness, a conference center and garage. Using data-tracking, multiple site visits, and analysis through CEE's proprietary energy-tracking software, CEE identified several major savings opportunities. CEE also found that the Ivy's "free-cooling" system, designed to capitalize on weather and reduce chilled water use during cooler months, was not functioning properly.

CEE's engineers have worked on 900 commercial buildings, small and large, not including the 1.4-million-square-foot IDS Center, saving clients an average of $200,000 per year with an average payback period of three years, as well as related environmental benefits. The agency also has worked with 65,000 homeowners.

Neal St. Anthony • 612-673-7144