HVAC Design Solves Humidity Woes at Indoor Pool/Ice Rink
September 15, 2008
NEW YORK - The most striking feature of the new $60 million Flushing Meadows Corona Park Pool & Ice Rink is its 20-foot-high wall of windows that affords a panoramic view of the surrounding New York City urban oasis of natural beauty, but it wouldn’t be possible without the project engineer’s HVAC design.
Flack + Kurtz, New York, designed separate state-of-the-art HVAC systems that not only keep the Olympic sized pool and natatorium’s 170-foot-long wall of windows clear of condensation and the ice rink free of fog regardless of outdoor temperatures, but also include an energy-saving green strategy utilizing heat recovery.
The 1,255-acre site is home to tennis’s U.S. Open and baseball’s Shea Stadium, but was once a city dump where trash was burned and shoveled onto 100-foot-high hills during the early 20th century. After two World’s Fairs and a short term as the United Nations headquarters, the Queens-based park has been returned to its original natural beauty and is now New York’s largest. The newest addition, the 110,000-square-foot pool and rink facility might someday host competitive events if and when New York becomes an Olympic site.
Keeping the facility free of condensation was the responsibility of a mechanical design team led by Flack + Kurtz’ Gary Pomerantz, P.E., executive vice president, and Cathy Chang P.E., HVAC design engineer. Overseeing the project was Gregg Stanzione, senior project manager at general contractor, Bovis Lend Lease, New York.
The key to keeping the pool dehumidification at 50 to 52 percent rh are two RS-562 Dry-O-Tron® heat recovery dehumidifiers by indoor air quality equipment manufacturer, Dectron Inc., Roswell, Ga., both of which have a moisture removal capacity of 390 lbs/hr. Although 90-percent of the roof is supported by cable, the design team appropriated a conventionally supported flat rooftop to support the huge 45-foot-long, 10-foot-high units.
The rigging and placement of the huge units was the most challenging part of the project for mechanical contractor, Trystate Mechanical Inc., Yonkers, N.Y., according to senior project manager, Joe Romano.
The units also heat and cool the space to 86°F and help bolster the building’s sustainability strategy with heat recovery to provide free 84° pool water heating the majority of operation. An integral Raypak boiler, which provides on-demand supplementary pool heating, was factory-integrated along with condensers into each package dehumidifier for single-source responsibility. The unit was physically tested under simulated operating conditions of Corona Park in Dectron’s state-of-the-art factory testing laboratory.
“It makes a lot of sense … to have so many different functions (pool water heating, space cooling, dehumidification, etc.) integrated into one unit by one manufacturer and tested before it arrives on site,” said Chang, who worked with manufacturer’s representative, SRS Enterprises, Brooklyn, on customizing the dehumidification units.
Added Pomerantz, “We considered using the project’s two 1 million-Mbh domestic water boilers (Smith Cast Iron Boilers) to add supplemental pool water heating through a heat exchanger, but running supply and return pool circulation piping to the roof would have raised the HVAC installation costs considerably.”
AIR CONTROLAnother energy-saving feature Flack + Kurtz specified was the Smart Saver factory-installed at Dectron, which uses warm exhaust air to preheat incoming outdoor air. Outside air is efficiently controlled and gauged by the number of occupants, time of day, and/or by CO2 sensors when a capacity of 500 spectators attends events.
Besides dehumidification, the Flack + Kurtz team also worked with the project architects HOM + Goldman, New York, and Handel Architects, New York, to specify extra condensation safeguarding with triple-glazed windows by Kawneer, and thermally broken mullions.
Airflow in a highly evaporative space such as a natatorium is critical. Flack + Kurtz value engineered the air distribution system with the specification of DuctSox fabric ductwork, which saved the project approximately 75 percent in installation labor and material costs versus conventional metal duct. The air distribution design is perimeter dual parallel duct with Comfort-Flow, which distributes 85 percent of the air through a linear diffuser running the entire duct length and 15 percent through the fabric to prevent condensation from forming.
The outer loop washes the walls and windows with its linear diffuser, while the inner run washes the ceiling. Eliminating hot spots is Flack + Kurtz’s return air strategy which places four grilles high above the spectator section and a linear grille midway on the same wall.
Additionally, the specified Sedona-SM model has a built-in anti-microbial fabric treatment that prevents mold/mildew from harboring in the ductwork’s fibers. This will improve IAQ as well as eliminate the need for periodical painting with toxic coatings that are required with metal duct to prevent premature corrosion in humid environments.
Since the overhead ductwork broadcasts warm dry air on the upper half of the windows, additional heating for the bottom portion is provided by hydronic baseboard heating from Sterling Hydronics, Westfield, Mass. Under deck air distribution with metal ducts was considered, however, hydronic baseboard was considered a value-engineered alternative that could heat the bottom half of the windows equally well. Additionally, under deck duct diffusers are a notorious maintenance problem because they collect dirt, water, and debris, according to Pomerantz.
While the rink and pool are housed in the same complex, their HVAC systems and particularly their mandatory vapor barriers are positioned significantly differently. “The key was to design the building envelope so that there were no weak points where moisture or condensation could migrate,” said Pomerantz.
To eliminate moisture exfiltration during winter, the 18,000-square-foot natatorium’s vapor barrier is positioned just inside the interior walls followed by insulation and high R-factor foam-filled concrete panel exterior walls. Conversely, the 14,000-square-foot ice rink’s vapor barrier is positioned next to the exterior concrete walls followed by insulation and the interior walls to prevent moisture infiltration during humid summers. Since the pool has a higher dew point than the rink, the wall separating the two rooms has a pool vapor barrier positioning.
Besides vapor barrier placement, another concern was the two 180-foot-high towers that penetrate through the top of the structure to anchor a series of roof support cables. Consequently, the poles become temperature transfers during extreme outdoor temperature conditions that are vastly different than the interior dew points. Thus, Flack + Kurtz conceived an innovative system of Chromalox electric contact heaters that would keep the towers even tempered and above interior dew points to eliminate condensation.
Like the pool, the ice rink requires dehumidification to eliminate humidity that commonly occurs not from evaporating water, but due to humidity generated by skaters’ respiration as well that of a 400-spectator section capacity. Flack + Kurtz specified a Dectron RK-120 Dry-O-Tron customized with an enthalpy wheel option to keep a design set point of 60°F and 40- to 50-percent rh. To eliminate fogging at ice level that’s common in rinks and keep condensation from forming on the ceiling, two ceiling-hung DA-2 Dry-O-Tron dehumidification units control fog. “We wanted to keep all the dehumidification equipment on the site under one manufacturer and one methodology - mechanical versus desiccant - which would make future maintenance and service easier,” said Chang.
Flack + Kurtz also did an energy study during the project design and found mechanical dehumidification would save the facility significantly in annual operating costs versus desiccant, according to Pomerantz.
Other HVAC equipment on the project includes Greenheck exhaust fans and Carrier conventional DX equipment for air conditioning and heating the complex’s small meeting rooms and offices.
If the Olympics come to New York in the future, the Corona Park facility will be a showcase of engineering for the rest of the world to see.
Publication date: 09/15/2008