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HVAC Engineer and Architect Revive Building IAQ and Save College Natatorium

May 9, 2001
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This Dry-O-Tron was custom painted by Dectron for the College of Charleston's historic district compliances.

CHARLESTON, S.C. - From its inception in 1973, a student center at the College of Charleston suffered the effects of high humidity and chemical odor infiltration from the facility's natatorium. Not only was the indoor air quality (IAQ) problematic for students using the building's ballroom, snack shop, or student government offices, but the roof, walls, and hardware such as doors, drinking fountains, and lockers had slowly corroded from excess moisture.

After some unsuccessful attempts at correction, college officials finally considered the 28-year-old pool building for adaptive reuse. A new multi-million dollar natatorium for the Cougars Swim Team and student swimming was in the planning stages until an advisory consortium led by professional consultant, Robert M. Stafford Inc., Columbia, S.C., convinced college officials of a more economical solution.

Stafford's project architect, Blount Shepard added the technical advice of renowned indoor pool IAQ expert, Stephen Kelly, The Kelly Group, Charlotte, N.C.; mechanical contractor, Cullum Constructors, Charleston, S.C.; and engineers from indoor air quality manufacturer, Dectron International, Roswell, Ga., proposed renovating the deteriorated parts of the building, installing a state-of-the-art dehumidification system and redesigning the HVAC air distribution for a project cost of $1.7 million-a considerable bargain when compared to erecting a new structure. Additionally, the college would save more construction money by not having to readapt the existing natatorium to another use.

The consortium was so confident of reversing the building's IAQ woes that it promised the college it could hold social events in the natatorium, which aside from the many IAQ problems was an aesthetically pleasing area with three walls of windows. "The building was so uncomfortable, the college was going to build an entirely new natatorium, but now the building's IAQ has improved to the point where they use the swimming pool area for social events and parties as well as swimming," said Kelly, who has designed multiple natatoriums and was a leader in the original development of dehumidification/heat recovery application technology.

"The difference in the facility before and after the renovation is like comparing apples to oranges," said Bruce Zimmerman, College of Charleston swim coach, "Previously the walls and windows dripped constantly with condensation, the smell of chlorine was very evident, and the locker rooms were either too hot or too cold. Now it's a very comfortable facility with 49 percent relative humidity and constant air movement."

The original HVAC design of the 47,000-square-foot, four-level Stern Student Center, which was built before modern day dehumidification equipment became popular, combined a make-up air unit with the college's central plant steam and chilled water loops. The chilled water loop is an excellent strategy for space air conditioning, but falls short when attempting to extract the excess moisture caused by the high evaporative rates of indoor swimming pools, according to Kelly. Since the original design inefficiently called for large amounts of exhaust air, an add-on desiccant system was installed seven years ago to recover energy. However it never operated correctly and was disconnected after six months of operation.

R.M. Stafford first entered the project with a moisture infiltration investigation and later became the engineering/architectural firm for the repair project. In addition to coordinating the HVAC redesign, R.M. Stafford also designed the replacement roof system and cladding of the parapet wall; replacement of the copper batten seam roofing and siding panels; repair of the exterior brick veneer, flashing and control joints; and coordinated the replacement of the deteriorated pool equipment.

For the first time since 1973, the College of Charleston's pool windows are clear and free of condensation.
With the building's envelope tightened, Kelly and mechanical contractor, Cullum Constructors, went to work updating the HVAC system. Anchoring the HVAC's redesign is a Dectron DRY-0-TRONâ„¢ model RS-362, which was carefully located on a loadbearing position of the low slope roof. The 28,000-cfm, 400-lb./hr make-up air dehumidifier recovers energy to heat the 25-meter, six-lane pool's water, plus it also heats, cools and provides outdoor air to the natatorium space.

The unit was sized to flexibly accommodate three functions-general swimming, swim meets with 250 spectators, and formal gatherings and social events. Typically a pool space has a two-degree differential between the air (84 degrees F) and pool water (82 degrees F) temperatures. However, bringing the air temperature down to 76 degrees Farenheit for occasional social gatherings puts an exceptionally high load on the dehumidifier that Kelly calculated into the project's equipment sizing.

Accommodating such a wide differential presented many challenges in sizing, but operational interfacing with the campus' automated control system by Siemens Building Technologies, Buffalo Grove, IL, solved the problem. "We ordered the pool heat exchanger with a bypass, plus the air side coil and condenser for 100 percent heat rejection," said Kelly. "Getting all these functions interfaced with the building automation system presented some difficult programming. We've specified Dectron dehumidifiers for over 30 pool projects, but this unit certainly had the largest array of custom components and functions."

Dectron even custom-painted the unit and the outdoor condenser a sand-beige color to integrate in more into the building's exterior materials-all of which complied with Charleston's strict historic district criteria.

Additionally, natatorium retrofits are difficult because an existing building offers no space for new air distribution ductwork. R.M. Stafford however, found a fourth floor storage closet space that acts as a supply/return duct chase for the rooftop unit. Concealing ductwork in a dropped ceiling, routing it around existing steel bar joints, and fabricating custom flat oval aluminum ductwork was Cullum Constructors' most difficult installation challenge, according to project manager, Robby Beaver. Special scaffolding was erected to navigate in and around the pool area during the duct and ceiling installation.

Kelly and Cullum designed the duct to blow conditioned air down evenly on the facility's three walls of glazing. "The southern wall's greenhouse and balcony-level sliding glass doors give the natatorium a wonderful aesthetic as well as a visual gateway to a lush, adjacent courtyard," said Shepard. "Previously none of this could be seen because the windows were constantly covered with condensation."

Another Kelly innovation was the correction of poor locker room IAQ with a Dectron model DK-60 1 00-percent outside air make-up air dehumidifier, which simultaneously recovers heat to pre-heat 240,000 gallons/yr. of shower water at an annual savings of $1,850. When unoccupied, the locker rooms are cooled or heated via the campus' chilled water loop or steam loop. When moisture levels rise due to locker room use, a humidistat activates a compact vertical Dectron dehumidifier that was installed in the cramped space of the original mechanical room.

Available space for redistributing the locker room air could have been problematic if it had not been for the fact that the pool was originally built on columns and beams because of Charleston's high water table. This resulted in a six-foot-high crawl space below the bottom of the elevated monolithic concrete pool. Because of the ample space, Cullum Constructors was able to install two Trane Co., Tyler, Texas, chilled water/hot water air handlers and ancillary ductwork, which distributes the conditioned air from the Dectron dehumidifier to each respective locker room.

Now the building is dry and free from the previous pool chemical odors it experienced. The college has not only saved the natatorium, but it has gained a space with expanded uses.

Publication date: 05/14/2001

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