Improving air comfort for swimmers
Typically, natatoriums should operate at four-to-six ACPH; however, the CAC’s original design fell short of this goal. The fewer air changes, and the pool industry’s growing challenge of controlling chloramines for better indoor air quality, prompted the design team to tackle both issues in the retrofit.
To do this, as mentioned previously, the design team built an additional 67-m2 (720-sf) mechanical room onto the side of the natatorium. Positioning the equipment at ground level inside a mechanical room, versus a rooftop installation, was more expensive, but less exposed to outdoor elements. A new mechanical room offered an energy-saving climate controlled environment, easier maintenance access—especially during winter conditions—and created an esthetic exterior to the building by concealing the equipment.
The energy-efficient, 32-ton unit dehumidifies the space to 50 per cent RH, uses compressor recovered heat for free 26 C (80 F) pool water heating, cools and heats the space to 27 C (82 F), and uses exhaust air to pre-heat the outdoor ventilation air. In the event of extreme cold weather, the natatorium can tap into the pool’s 995-MBH (thousand [British thermal units (Btus)] per hour) hot water/pool water heat exchanger for additional heating.
As per the aquatic supervisor’s request, the HVAC system now offers staff the ability to customize the environment to match a specific activity. For example, the dehumidifier’s capacity was sized larger by the design team for more demanding swim period humidity loads, such as warmer water and space temperatures for senior swimming, or cooler water and space temperatures during swim meets. Those parameters were unreachable with the original units.
Virtually eliminating chloramines
Today, chloramines and the respiratory irritation (called granulomatous pneumonitis and sometimes referred to as Lifeguard Lung) they inflict on swimmers are challenging the entire indoor pool industry. Chloramines are created from the chemical bonding formation of chlorine molecules and organic contaminates. The bond creates a heavy gas that stratifies, just above the water surface, in the swimmers’ breathing zone, making it difficult to remove even in ideal natatorium ventilation designs.
There are commercial products designed to exhaust chloramines off pool water surfaces, however. In new construction, these systems are integrated into the gutter in the pool wall and connected to an underdeck exhaust duct. In retrofit situations, they are secured to the top of the pool deck and exhausted through a flexible on-deck duct.
Since the CAC was undergoing a high-cost HVAC renovation, the design team innovatively created a dual-purpose 9.1-m (84-ft) concrete bench for swimmers along a wall nearest the pool surface. The bench’s secondary purpose was to draw chloramines from the pool surface through dozens of perforated metal openings located in the face of its masonry infrastructure. The bench’s interior plenum delivers the return air to the new mechanical room’s dehumidifier for heat recovery and exhaust via an underground concrete tunnel built as part of the project.
An additional deterrent to the accumulation of chloramines is an ultraviolet (UV) water sanitation system. When combined with the ventilation ductwork redesign, the bench and the UV system have eliminated almost all traces of chloramines in the pool area.
