When you step into the Decatur, Illinois, public library on a scorching summer day, you’re not just entering a haven for books – you’re walking into a cooling center. That function, as it turns out, shaped every step of a recent, unusually complex HVAC retrofit.
The library occupies a former Sears building, repurposed decades ago. Its bones are sturdy, but its original chiller system had “outlived itself,” as Colin Brinkoetter, project manager at E.L. Pruitt Co., put it. E.L. Pruitt served as general contractor on the job, handling everything from coordinating subcontractors to overseeing the installation itself. “It was time to update and go to newer technology to save money and improve efficiency.”
The old system had started to fail, leaving the city and library staff facing rising maintenance headaches and unreliable cooling.
Patrick Corrigan, the design engineer from Architectural Expressions LLP, explained that libraries serve a special public role during extreme heat.
MODULAR CHILLERS: A row of modular, stackable chillers provides built-in redundancy – keeping the library cool even if one unit needs maintenance. (Courtesy of E.L. Pruitt Co.)
“The library needs to remain functional as a cooling center during hot days,” Corrigan said. “Some reliability needs to be built into the design. Some redundancy.”
That meant the team couldn’t just swap out the old chiller for any off-the-shelf replacement – they needed a system that would be dependable, easy to maintain, and ready for the public.
After years of planning and collaboration with city staff, the team landed on an adiabatic fluid cooler paired with modular, stackable chillers. Unlike traditional cooling towers, which rely on constantly evaporating large amounts of water to shed heat, the adiabatic fluid cooler draws air through a condenser coil to cool the circulating fluid. On most days, it works like a giant radiator, using outside air alone. Only during the hottest periods does it briefly spray water onto pads on the entering air side of the coils to boost cooling – slashing water use and risks from bacteria at the same time.
Compared to the old open cooling tower, the new setup “doesn’t require chemical treatment anymore, and your Legionella risk goes away,” Corrigan explained. That’s not a small thing for a public building where many visitors may be vulnerable to respiratory illness. Plus, “the water consumption is a huge reduction – about 5% of what the old tower used.”
EFFICIENCY UPGRADE: The new chiller modules are designed for efficiency and flexibility – ready to handle the library’s varying cooling demands throughout the year. (Courtesy of E.L. Pruitt Co.)
Smart Design, Smoother Maintenance
There were practical benefits for the city’s maintenance staff, too. “We wanted to leave them with less maintenance headaches going forward,” Corrigan said. The closed system is “pretty maintenance free,” with the main task being changing out filtration pads – a job that only needs doing every couple of years, unless the equipment is exposed to a lot of dust or airborne debris.
The retrofit itself was no minor feat. Crews constructed a new superstructure on the roof to elevate the equipment and built a walkable service area around it. Inside, old and abandoned equipment was stripped out, freeing up space and making room for the new, more powerful pumps needed for the closed system. The modular chiller approach gives the library built-in redundancy, so it can keep cooling even if one unit goes down.
Along with the visible superstructure and rooftop units, the upgrade included new and larger pumps to handle increased pressure in the closed loop system, as well as a buffer tank to smooth out rapid changes in cooling demand. “We used a modular chiller approach to give the library redundancy built into the system,” Corrigan explained. These technical changes – new piping, bigger pumps, the buffer tank, and the modular chillers themselves – are all visible in photos from the job site, highlighting the scale and complexity of the retrofit.
ROOFTOP COOLERS: Two adiabatic fluid coolers sit atop a new superstructure on the roof – using outside air, and only minimal water, to keep the system running efficiently. (Courtesy of E.L. Pruitt Co.)
Installation was carefully timed around the seasons. “You start a project like this in the wintertime and get your new equipment up and ready so that it’s ready to rock in spring,” Brinkoetter said. That meant orchestrating large crane lifts, opening up walls, and coordinating with several subcontractors to keep everything moving.
The project was a first in some respects – pairing this specific chiller and fluid cooler together was new for Corrigan’s team, even though they’d worked with the manufacturers before. “It was nice to see the two paired up,” he said, as the commissioning process was taking place in June.
Brinkoetter made sure to credit all players involved. “The supplier of the chiller was Rollie Johnson, Inc. Christy Fultz did carpentry. Bodine Electric on electrical. And the city’s been a great customer – Mike Pritchett and the whole team.”
For Corrigan, the project is a sign that newer, more efficient cooling technology is gaining traction in the region. “We like to see more of these come to the area,” he said.
The library’s new system may not be visible to most visitors, but for those who rely on the building’s comfort – or just want to escape the heat – it’s a quiet revolution in public infrastructure, built on engineering, teamwork, and a lot of planning behind the scenes.
NEW PIPING: New piping routes chilled water throughout the building – connecting the modular chillers to the rooftop fluid coolers and buffer tank. (Courtesy of E.L. Pruitt Co.)