By Matt Baker
Prudential Plaza is a two building office complex on prime real estate overlooking Millennium Park. Prudential One (or as tenant and staff sometimes refer to it, Pru 1) was constructed in 1955. At forty-four stories, it was the tallest building in the city at the time and featured an observation deck, now closed. Prudential Two (Pru 2) was built in 1990. With its recessed chevrons and pyramid topper, the fifty-eight story younger sibling received several design awards, including Best Structure from the Structural Engineers Association of Illinois.
These two iconic buildings are recognizable components of the Chicago skyline. Now they also have joined the ranks of local landmarks to go green; this summer, Prudential Plaza was awarded LEED-EB Gold by the USGBC.
Though already a relatively easy sell, the buildings’ ownership, Los Angeles-based Bentley Forbes, felt that achieving LEED certification would create a new selling point to an increasingly savvy market. “We figured we would get looks from prospects that we wouldn’t otherwise get,” said John King, the Prudential Plaza Property Manager. “Even for some of our existing tenants, being LEED certified is a consideration for renewals.”
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One behavior in need of modification was tenant activity. Bentley Forbes promoted a bike to work program and, through the City of Chicago, began hosting a weekly farmers market in the plaza. The management company also held tenant meetings to discuss the LEED process and energy savings initiatives. The message was clear: going green would benefit both company budgets and the environment.
One strong example of this is PruCycle, a bulletin board where tenants can post items that they don’t need such as office furniture or supplies. Other tenants can browse the website to see if there is anything they need or could put to use. This system gives items a second life and promotes reuse over disposal. Centralized collection points for batteries and plastic bags, as well as building-wide recycling also give tenants an opportunity to practice sustainability.
Bentley Forbes partnered with Office Depot to form a green office supplies purchasing consortium. The voluntary program allows Prudential Plaza to leverage the purchasing power of all 7,500 occupants and command lower prices on green office supplies. King views this as a way to go green while promoting the bottom line. “Marrying the corporate interest and the environmental interest was an interesting selling point for LEED.” Roughly 40% of tenants are currently engaged in the consortium.
One daunting task was to create a sustainability plan for two very different buildings. When Pru 2 went up in the nineties, the older Pru 1 had many of its systems upgraded. “It’s not as old as the façade would suggest,” said King. Nevertheless, Pru 1 uses natural gas for heating while Pru 2 is all electric; river water chills the older building while Pru 2 uses a more traditional cooling tower.
Seeking consultation, Bentley Forbes enlisted the help of local non-profit the Delta Institute. They were attracted to the firm based on their work guiding the Merchandise Mart and other legacy buildings through the LEED process. “A lot of people can come in and read from the LEED requirement book,” said King. “What they were able to do was to really help us to understand what the USGBC is looking for.” Wisconsin-based Envise Energy performed the mechanical commissioning and the Delta Institute guided the buildings’ engineering crew through LEED certification and an overhaul of the plaza’s energy initiatives.
In Pru 2, the building engineers locked out the electric heat panels. “They’re not intended to run during the summer,” King explained, “but over the years, we’ve found that as items fall out of calibration, they just tend to run all the time.” This is a common problem, but by identifying it, they were able to put a new procedure in place, reconfigure some new infrastructure and save about 10% of the annual energy usage.
The natural gas system in Pru 1 provided different challenges, including one quirk not unusual in high rises. “They tend to both heat and cool at the same time. Which, as you can imagine, is extremely wasteful,” King said. Traditionally, the building had to run a gas-fired boiler to heat all the domestic water. The installation of spot hot water heaters in all of the public restrooms enabled the building engineers to completely turn off the boiler except when needed in the winter. This change cut annual natural gas consumption by over 30%.
Modern lighting controls such as time clocks and motion sensors in the common areas provided better control over electricity usage. While making these upgrades, Prudential Plaza management converted many common area fluorescent lamps from T12 to T8. T8 lamps will typically use about a third less energy than the larger bulbs, so this is fairly common when performing a lighting upgrade. But, Prudential Plaza took this initiative a step further in the airwells, building service areas as well the parking garage by removing one lamp from each fixtures. With the reflectors, these areas still had plenty of light and the move eliminated about 1,200 light bulbs per purchasing cycle. “And we were able to get a much quicker payback on the lighting retrofit,” King added.
Partially levied by a ComEd incentive program, Prudential Plaza also upgraded to variable frequency drives, giving them better control over the heating and air systems. Smart meters set up through the utility provide hourly interval data for all of the buildings’ systems. This helped identify systems that were running continuously or more than demanded. “On an annual basis, we were able to save well over a million dollars,” said King. “That in and of itself helped more than pay back any of our LEED costs.” Smart meters don’t just identify problem systems; they can self diagnose as well. A look at the data showed one ComEd meter that was spinning seven times the speed it was supposed to. Prudential Plaza secured a rebate from the utility once this was pointed out.
Bentley Forbes explored the possibility of installing a rainwater cistern atop Pru 1, but the relatively cheap cost of water in the region put the payback too far into the future. They achieved water savings in other ways, such as the introduction of hands-free faucets in all the restrooms. By enhancing the mechanical cross connect between the two structures, building engineers were able to shut down the cooling towers in Pru 2 during milder weather and run the building on Pru 1’s river water system.
The primary goal of bringing Prudential Plaza into the sustainable movement may have been marketing to prospective lessees and tenant retention. But the numbers don’t lie, and reducing the building complex’s utility usage so dramatically was itself worth gold.