MGE Talks Business Newsletter

Matt Darga, Urban Land Interests, worked on updates to the U.S. Bank building that are on track to cut energy use by 35% to 40%, at an annual savings of roughly $350,000.

"If you want to run a building more effectively, you have to crawl into the nooks and crannies," said Darga, facility operations manager at developer Urban Land Interests (ULI), the building's owner since 2008. "You need to know how a building is supposed to operate – and how it actually does – before you can make it better."

Built in 1973 – and originally known as the First Wisconsin Plaza – the angled and glass-sided building at the corner of East Washington Avenue and Pinckney Street was lauded for its unique look and quickly became a Madison landmark. But as the ULI team learned, good looks don't always translate into efficient operations.

The building's design was intended to be energy efficient, said Brad Binkowski, principal at ULI. The facade was valued for its daylighting properties (using natural light instead of electric lighting) without the appreciation of how much heat that amount of clear glass would bring into the building.

The glass exterior turned the building into a hothouse, and a previous owner's addition of window films and blinds did little to solve the problem.

"Some of the atria were being used as greenhouses – plants were the only thing that could tolerate the temperatures," Binkowski said. "The spaces that were supposed to be premier spots in the building lost a lot of value."

"The building's original HVAC system was ill-equipped to handle the large temperature variations between the building's core and peripheral spaces which meant the system had to literally work overtime," said Darga. In fact, it had gotten to a point where the HVAC system was running all day, and through the night, in an attempt to preheat or precool spaces so they'd be tolerable when they were occupied.

ULI knew that changes were in order to return the building to its position as Class A office space, the most prestigious of the three office space ratings. "We wanted to be a steward of this building because of its pedigree and its location on the Capitol Square," said Binkowski, "but we also needed to be fiscally responsible."

Putting in better glass throughout the building was an obvious choice from an energy efficiency standpoint, but if that were the only change, the payback would be hard to swallow. "We're talking 30 years," said Darga, "and no one will touch that."

Instead, ULI took a holistic approach that used a combination of hands-on investigation and finely tuned computer energy modeling to determine the most effective ways to increase useable space and improve energy efficiency.

A revamp of the exterior. Instead of the original angled faces on the atria side of the building, ULI came up with a new design that integrated vertical walls and rooftop terraces. "The insulated roofs mean less glass and a reduced solar load, plus we've created valuable outdoor space for tenants," said Binkowski.

The redesign meant that it made financial sense to switch about 30% of the building's facade to energy-efficient glass. "The incremental cost of new solar-efficient glass was very low," said Darga. "We now have a seven- to eight-year payback—plus the long-term energy benefits of the new glass—and we've created a more comfortable building for our tenants."

Conversion to a variable air volume (VAV) system. Like many older Class A office buildings, U.S. Bank had a constant volume reheat system with fans that ran continuously, all day and all night. The conversion to a VAV system offers several benefits: the fan modulates building air flow to provide only the necessary amount of cooling, and in those areas that are overcooled—usually rooms away from the windows or interior zones—energy used for reheating is minimized.

Installation of direct digital controls (DDC) and upgrade of the building automation system (BAS). The building originally had a pneumatic control system which used air pressure and a system of pressure-driven switches and devices to provide basic logic control to HVAC components. Although the system might have been the "latest and greatest" at the time the building first opened, this technology is outdated and the knowledge base to service and operate the systems is fading as experienced staff retire. Plus, as the systems age, dirt or water in the lines and devices can disable the controllers.

Today, most systems use digital logic or direct digital controls. These systems allow better control of more parts of the system and are more robust. They also allow the operator to create a graphic representation of the HVAC system which makes it easier to understand and control system components.

"Our new system of unified, computerized controls gives us greater flexibility and scope in programming schedules, temperatures and operating sequences," said Darga. "It minimizes the man-hours needed for building operation and greatly improves the efficiency."

Upgrade of the cooling tower and chillers. Chiller technology has improved over time and most of today's models are 20% to 30% more efficient than older ones. Chiller improvements include variable flow through the evaporators, increased heat exchanger surface area and improved controls that help to maintain high efficiency levels even at lower capacities.

ULI chose cooling towers that can accommodate three high-efficiency chillers—although the building currently only has two. "We own the Tenney building next door, and eventually, we hope to add a third chiller (for that building) and run it off this mechanical plant, which will be extremely efficient," said Darga.

These chillers will save approximately $50,000 in energy costs each year. And they're now more centrally located near the loading dock, rather than the highly desirable ninth-floor space that they used to occupy.

Addition of a waterside economizer (free cooling) chiller system. While homes and small commercial buildings typically only need cooling in the summer, larger buildings like U.S. Bank require some level of cooling much of the year because of the amount of heat from equipment, lights and people. And this is especially true for buildings with a lot of glass.

Instead of using only the chillers to generate cooling, ULI added a waterside economizer to its system. This allows cool outdoor air to provide building cooling which is a "free"—or at least, less costly!—way to cool.

"Plus, we can rely on the combination of the waterside economizer and the cooling tower to maintain space temperatures during non-peak cooling periods—like spring and fall—rather than running the large chillers," said Darga.

Building improvements have ULI on track to cut energy usage by 35% to 40%, at an annual savings of roughly $350,000. The building has already been certified as an ENERGY STAR® building which means that it meets energy efficiency standards established by this program which is run jointly by the U.S. Environmental Protection Agency and the U.S. Department of Energy. ULI also hopes it will achieve LEED (Leadership in Energy Environmental Design) certification, probably at the Silver level. LEED is a third-party certification program of the U.S. Green Building Council for the design, construction and operation of high-performance green buildings.

Existing tenants are thrilled with the new levels of comfort and usable space, and the building has even attracted some new ones, including one of Madison's premier restaurants, L'Etoile.