The Alamo is the most photographed building in Texas. But the next edifice on the photo-op list isn’t as obvious. It’s not the site of an epic battle. It’s not a towering skyscraper. And no, it’s not the Southfork Ranch. The second-most photographed building in the Lone Star State is the historic Ellis County Courthouse in Waxahachie. If that community doesn’t immediately register on your geographic barometer, it’s a town of around 21,000 about 30 miles south of Dallas, perhaps most noted as the location of the ambitious but abandoned Supercolliding Superconductor project.
Unlike that project, however, the courthouse has withstood the test of time. The three-story granite and limestone structure, built in 1895, still serves proudly in the center of the town square. But after more than a century of service, it suffered from poor, outdated building systems. Despite its majestic exterior—replete with ornate, hand-carved column capitals and accent pieces—and its bright, colorful interior, the courthouse was in dire need of major mechanical, electrical, plumbing and life-safety upgrades. Quite simply, it needed new systems to match its aesthetic and historical splendor.
Fortunately, the powers that be in the state of Texas recognized the need for restoration of their many historic justice facilities and solicited applications for funds to assist with architectural and systems renovations. The Ellis County Courthouse was granted such funds and in late 1998, restoration work began. O’Dea, Lynch, Abbattista Consulting Engineers, P.C., (OLA) was selected to perform the building system work. The New York-based firm had an office in nearby Dallas and had already performed similar work on several other Texas courthouses.
Going to court is often an unpleasant experience. Compound that with a packed room, no real air-conditioning system and a hot and humid Texas summer, and you had the Ellis County Courthouse. “[The HVAC system] was a hodge-podge,” says Steven Abbattista, P.E., vice president of OLA and the firm’s principal in charge of the project. “There was no central AC system. There were only some window units here and some split systems there. It was just a mess.”
Having been constructed in an era when there was no air conditioning, the courthouse’s original designers relied mainly on the building’s masonry exterior to retain coolness. But when it came to modernizing the structure, the once practical and beautiful facade presented issues of its own. The building’s historic interior also proved a challenge, in that the county didn’t want a lot of visible heavy-duty ductwork.
The solution presented itself in the form of a four-pipe fan coil system coupled with a central chiller/boiler system. Its major advantage was the ability to provide lower cooling—and higher heating—water supply temperatures, which in turn, allowed for reduced airflows. This resulted in smaller ductwork, which gave the designers more flexibility with concealing and routing ducts. Additionally, the lower coil temperatures helped to accommodate lower sensible-to-total-heat ratios associated with heavy masonry and plaster construction, which yields a high thermal mass.
As far as the cooling load itself, much of it was set to meet code-required ventilation rates during peak cooling times, resulting in relatively high latent loads compared to the sensible load on the building. The county also required OLA to build in equipment redundancy and operating efficiency, which prompted the firm to select a two-circuit chiller. This setup allows the building load to be carried on one circuit, operating at its optimum efficiency for most of the year. The second refrigerant circuit kicks in during peak periods, creating redundancy in the event of a single compressor failure in a peak cooling period. This configuration also rotates chiller circuit use for even equipment wear.
On the subject of optimum efficiency, the project threw OLA designers a curve in that the HVAC system would also have to condition several large courtrooms that are unoccupied for the majority of the year. To minimize energy consumption, a CO 2 detection system was specified to modulate outside air intake dampers on the fan coil units that serve the courtrooms. This meets ASHRAE’s indoor air quality standards while simultaneously reducing cooling and heating requirements when these spaces aren’t fully occupied.
In general, the courthouse is governed by a direct-digital control (DDC)-based building automation system that regulates chilled heating and water supply quantities and resets supply water temperature set points based on outside air temperature. The BAS also monitors chiller and boiler operation and maintains building air pressure. Excess air is relieved into the attic during high occupancy periods with their concurrent high ventilation rates, and a central attic ventilation system maintains a constant differential pressure between the attic and outdoor air.
Off site, but close at hand
As noted earlier, the HVAC system’s low temperature capabilities helped reduce the size of duct work, but that didn’t solve the problem as to where to store major mechanical equipment. So as not to take up valuable floor space in the building, as well as for reasons of unsightliness, the boiler was relocated to the original boiler room from its location in the middle of the basement, and the chiller was placed off site. According to Steve Gumm, P.E., of OLA’s Dallas office, the original plan called for the chiller to be housed in a building, under construction at the time, five blocks from the courthouse. When that plan fell through, the firm had to find another location for the equipment and settled on an empty lot across the street.
The chiller sits below-grade in a sound-attenuated vault that’s topped by a metal grate. Also located in the lot, but above grade within a brick enclosure, is the building’s emergency power generator and its fuel supply. A utility transformer is similarly sited. Plans are in place to erect a public restroom facility in front of the equipment that, in effect, will hide it from the street.
The final challenge in modernizing the courthouse’s HVAC system was getting the heating and chilling capacity to the building itself. It meant digging up the street, which turned out to be a descent into the unknown. “Typically, when you dig a street and put new utilities in, you have an idea of what’s there,” said Abbattista. “But the stuff there was so old, nobody really knew what we were going to find. Really, they were digging somewhat blind.”
At first, a more typical civil plan—considering where to dig and where to install the new pipes and conduits in relation to the old—was a possibility, according to Abbattista, but proved moot since the existing utility information was incomplete. The plan eventually required a complete excavation of the street so new water pipes and emergency and utility power feeders could be laid between the equipment vault and the courthouse.
An alternative to sprinklers
Like the air conditioning conundrum, modern life-safety systems, such as sprinklers, were non-existent in the late 1800s. Needless to say, they were missing in the building. In fact, there was only one means of egress from the upper floors and no elevator. The building needed to see many upgrades from a fire and life-safety standpoint to come into compliance with current codes.
But to make matters more challenging, sprinklers were not an option for aesthetic reasons. “The architect and the Texas Historical Commission just did not want to see a bunch of exposed sprinkler piping,” said Abbattista.
Additionally, a sprinkler system would have called for more cutting and patching in the historically sensitive courtrooms, an undesirable task given the building’s structure. “Any cutting and patching in this building was a nightmare because you’re talking about 18- to 20-in. walls that are made of granite,” said Gumm.
In lieu of sprinklers, the team put together a package that included a second stairwell, an elevator, areas of refuge—equipped with call stations—for disabled persons at each elevator landing, pressurization of the secondary stairwell and a smoke purge system in the building’s main atrium stairwell. Some existing office space was removed for the new elevator and stairwell, as well as for wheelchair-accessible restrooms. A fully addressable fire-alarm system and an emergency generator for lights and elevator power were also installed.
The smoke evacuation system was designed to bring air into the building at the base of the atrium stairwell, which extends into the basement. Smoke is evacuated with assist fans through louvered faces in the bell tower—the highest point in the building. The bell tower also had to be sealed off from the attic.
In the end, the designers at OLA were able to install new building systems with little to no impact to the courthouse’s historical architecture. But though the Ellis County Courthouse maintains its 19th-century look and feel, it is the 21st-century infrastructure that will keep it safe, comfortable and preserved for decades, and perhaps another century, to come.
Out of Sight, but not Out of Mind
One of the crucial elements in renovating the Ellis County Courthouse in Waxahachie, Texas, was maintaining its historic look. That meant ductwork and mechanical equipment had to be tucked away.
This strategy is common to most projects, but for the staff at O’Dea, Lynch, Abbattista Consulting Engineers, P.C., New York, it was made much easier by the fact that the courthouse contained multiple “pockets” throughout its structure, the like of which are not common to most projects.
The courthouse was constructed in split-level fashion with the first floor accessible via four raised entrances at each of the cardinal compass points. Each entrance porch contained a crawl space below, where the design team placed mechanical fan coil equipment to serve the basement and first floor air-distribution systems. Also, the building’s steep roof created extra attic space above the third floor. Air-handling equipment for the second and third floors was placed in this space.
Main electrical conduits were run in the basement, attic and chases in order to keep them out of sight. Branch circuitry conduits were channeled into the walls and ceilings, requiring cutting and patching. In some cases, cable had to be installed within pre-fitted baseboards that matched existing floor moldings. “We had to pretty well have it mapped out on the drawing exactly where [wiring] was going to go and try to group it so that the contractors knew what they were getting into,” said Steven Abbattista, P.E., vice president of O’Dea, Lynch, Abbattista.
With creative use of these hidden spaces, the firm was able to keep equipment out of site while not using up valuable floor space.