In the last decade or two, we've become accustomed to seeing corporate names on ballparks and arenas (e.g., Comerica Park, Chase Field), but we have not been used to seeing them on the hallowed halls of our universities. That all changed in November 2003, when the University of Memphis opened the doors to its newest building, the FedEx Institute of Technology.
Contrary to its moniker, students taking classes in the building will not be studying how to deliver packages more easily and efficiently; instead, they will be embarking on advanced world-class interdisciplinary research in order to eventually become a new generation of highly skilled graduates.
The high-tech building required a state-of-the-art flexible HVAC system that would grow and change to suit the evolving needs of the university. That was a challenge in and of itself; however, the bigger challenge was the fact that nobody knew exactly how spaces within the building would be used. A room might hold five people or maybe 50; it could be filled with computers, or there might be no computers.
These unknowns led to the specification of an underfloor air distribution system (UFAD), which can adapt to changes in load easily and efficiently. High-efficiency chiller and boiler systems keep energy costs down, while a DDC system keeps everything under control.
A typical above-ceiling fan powered reheat box supplies air to the curtain wall via linear slots on the first floor. The first floor of the institute did not include an underfloor system and utilized a traditional overhead system; underfloor systems were used on the second, third, and fourth floors.
VAGUE GUIDELINES
When fully occupied, the 95,000 sq-ft, four-story FedEx Institute will house ten research centers that focus on an array of studies ranging from medical breakthroughs in cancer and alcoholism to artificial intelligence and RFID (radio frequency identification) tags in the supply-chain. Classrooms, computer labs, research centers, collaborative areas, meeting rooms, and exhibit spaces are located throughout the institute, as well as a cybercafé and a 200-seat fully interactive auditorium, which features video-conferencing capabilities, wireless Internet access, and a sophisticated audience-response system.Designed to teach the newest technologies using the most advanced techniques, the research and educational facility incorporates Wi-Fi capabilities and a Voiceover Internet Protocol network, as well as plasma-screen video-output throughout, and a 2.5-gigabit Internet connection to Oak Ridge National Laboratory.
Everything about the institute - including its exterior design - is high-tech. The university knew the building would be used to research emerging technologies, but it wasn't quite sure which companies would be leasing spaces. That caused some challenges for Jeff Haltom, P.E., a design engineer with Shappley Design Consultants in Memphis, who was responsible for designing the building's heating and cooling systems.
"The big problem we had was trying to pin the university down as to the building's exact function," said Haltom. "They said they wanted the most flexible building they could get and that just about anything could happen in the building, short of chemistry labs and biological lab functions. They also said that whatever was built may change the following year, so it had to be flexible."
These rather vague guidelines led Haltom and the architects, Looney Ricks Kiss and The Crump Firm, Inc., both of Memphis, to use the York FlexSys™ UFAD system. This system involves pressurizing a 12- to 18-in. raised floor cavity with conditioned air. The VAV diffusers are in the floor, so if a tenant needs to move walls, it's possible to modify the air conditioning system by simply moving around the floor tiles.
The UFAD system also made economic sense because the university had already planned to include a 6-in. raised floor in order to hide all the various wires and cables required for the high-tech building. Installing another 6 in. for the UFAD did not add that much to the budget.
An underfloor system would also enable the university to run the electronic cables and wires under the floor, while providing better control over air conditioning to spaces that would probably be reconfigured on a regular basis.
Since the university did not know how many tenants would be in each of the institute's rooms, the UFAD system was designed for the average, then spare floor boxes were bought and stored in a mechanical room. "If they decide they want to put 50 people in a room and we only planned for 15, all they need to do is pull out some spare floor boxes and pop them in the floor," said Haltom.
TIME AND ENERGY SAVER
In addition to being flexible, the UFAD system had two more benefits. First, it reduced the design time for the engineers and second, it saved energy for the university.Design time was reduced for the engineers, because ductwork was almost non-existent as compared to a conventional overhead system. "One advantage of the underfloor system is that it did away with ductwork routing problems," said Haltom. "Probably 50% of our design time is often spent just trying to figure out how do we get this large duct through this little bitty ceiling without screwing up what the architects want to see. Going with an underfloor system took all that effort away, which saved us a lot of design time and allowed us to focus on other issues."
Given that the AHU for each floor is located against one edge of the building, there was concern as to whether equal static pressure could be maintained throughout the floor plenum. To compensate for this, three ducts per floor were run to ensure that air would be delivered to the opposite edge of the building undisturbed by cables or anything else that would interfere with it. These three uninsulated duct runs total about 45 ft each, which might compare to 20 times as much duct for an overhead system.
In addition, the UFAD system does not require a fan-powered VAV box overhead to provide perimeter heating and cooling; instead, the system offers a fan-powered, electric-heat perimeter system, which eliminated the overhead system and all the constraints that go along with it.
As for energy savings, UFAD systems provide cooling supply air that is typically between 60°F to 65°, vs. a conventional system that cools the air to 55°. The higher supply air temperatures mean an increased ability to operate in economizer mode many more hours each year. In addition, space conditioning is only provided from the floor level to about 6 ft above the ground, which means energy isn't expended to cool the space near the ceiling.
The systems' energy efficiency was enhanced by the installation of a York MaxE™ 800-ton water-cooled centrifugal chiller with an OptiSpeed™ VSD and four Fulton 2 MMBtu condensing boilers. "We used variable flow through the boilers, which maximized our heating side energy savings," said Haltom. "We also used outside air economizers on all the airside equipment, so we could turn off the central plant whenever the outdoor air conditions will allow it."
CO2sensors and pressure controls were installed on all the equipment, due to the fact that the tenants' activities were unknown at the time of design. "We designed the coils in the air handlers for a worst-case scenario. We designed for heavy outdoor air, and the coils had to have that capacity," said Haltom. "That's also why we have two-way valves everywhere and variable flow on everything, because we were overdesigning for the worst case scenario. The CO2sensors and pressure controls allow us to run at the minimum whenever conditions permit."
The chiller was deliberately oversized for the institute, so that it could also supply chilled water to another building on campus. Steam and chilled water are also provided from the campus central plant for back-up purposes.
The central plant is located about one-quarter of a mile from the facility, but this arrangement did not require that new chilled or hot water piping be installed. Existing underground campus piping was already routed past the institute, so it was not difficult to tie into the system.
CONTROLS AND CHALLENGES
Anyone who works or lives with other people knows that disputes often arise over the temperature setting of a room. In this case, the temperature war will be fought from the comfort of the tenants' desks, because Web-based wireless thermostats were used. All computer users have thermostat icons on their screens, which allow them to raise or lower the temperature from their seats.Basically, the wireless thermostats become sensors, allowing occupants to adjust the temperature of the room via the Internet. These thermostats enhanced the flexibility of the system, because no wires need to be moved in case a tenant requires a different layout. If a thermostat is moved, the radio frequency is reassigned so the thermostat can be placed on any wall necessary.
The wireless thermostats are tied into a Johnson Controls Metasys system, which controls the institute as well as the equipment at the campus's central plant. The whole system is Web-based, making it easier for campus personnel to access the system. Sometimes perhaps it's a little too easy, as Haltom noted that anyone with the proper password can change the setpoints. Not surprisingly, this has caused a few problems, but additional training will hopefully solve these issues.
One of the bigger challenges that arose during construction was that many of the trades were unfamiliar with the UFAD system. In this type of system, the floor becomes equivalent to a piece of ductwork, therefore, it was necessary to make sure the underfloor plenum was sealed. It also needed to be kept clean of construction dust, as work progressed above the floor.
Jeff Smith, owner of Morgan and Turner in Memphis, the mechanical contractor for the project, noted, "We were constantly concerned with the leakage rate: the amount of air that leaks through cracks in the floor and around any electrical boxes or the air terminals themselves. It was critical to make sure the building envelope was sealed and that all the junction boxes had gasketing and were sealed properly."
Haltom noted that all the specifications stated that contractors must seal everything when finished, but that didn't always happen. "Everybody - from the electrical contractor to the controls contractor to the carpet installers - was poking holes in everything. We told them how the system needed to be sealed, but many didn't want to do it."
It is possible that some of the contractors didn't read the fine print regarding sealing in the specification, so most did not price it with that in mind. Unfortunately, the design time that was saved due to the reduced amount of ductwork was spent on the back end of the project, trying to seal up all the holes and making sure the pressurized floor work correctly.
But eventually, everything was sealed, construction was finished, and the systems work as planned. "It's a good system, and we all enjoyed working on the design," said Haltom. "It was a real challenge to take it from design to installation and operation, but we're proud of it."
