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Updating natatoriums for maximum occupant comfort

By Ralph Kittler, P.Eng.

Natatorium
Built more than 25 years ago, Forest Hills Public Schools Community and Aquatic Center (CAC) in Grand Rapids, Mich., a 111.5-m2 (12,000-sf) natatorium, needed two aging 24-ton dehumidifiers replaced.

The knowledge of what natatoriums require for a successful design has been upgraded dramatically in the last quarter century. Recent technological advancements and state-of-the-art engineering standards have not only made these improvements possible, but have also made significant improvements in indoor pools for spectators and swimmers.

In fact, managers of older community, high school, and private health club pools should review their facilities for energy-efficiency and environmental stewardship, as well as for optimized air distribution, to improve indoor air quality and comfort.

A case in point is the Forest Hills Public Schools Community and Aquatic Center (CAC) in Grand Rapids, Mich. Built more than 25 years ago, the CAC, a 111.5-m2 (12,000-sf) natatorium, needed two aging 24-ton dehumidifiers replaced. Rather than performing a drop-in replacement, the school district saw a building and equipment retrofit opportunity to upgrade the natatorium’s indoor air quality (IAQ), while also reducing future operational costs with state-of-the-art heating, ventilation, and air conditioning (HVAC) equipment.

“The difference in air comfort and quality for spectators, not to mention the swimmers after the retrofit has been incredible,” said Kelly Swieter, CPO, aquatic supervisor, Forest Hills Public Schools.

Modernizing the facility

Natatorium spectator area
The design team first looked at upgrade possibilities for the 300-seat spectator area.

The design team first looked at upgrade possibilities for the 300-seat, 223-m2 (2400-sf) spectator area. One unique HVAC challenge a natatorium presents versus more conventional spaces is some occupants are wet and are wearing only swimsuits, while others—especially during competitive events—are fully clothed spectators. This presents an air comfort challenge, especially because the ideal air temperature range for swimmers is approximately 26 to 27 C (80 to 82 F). The ideal spectator temperatures, however, are considerably lower.

Three design methods were available to accommodate this challenge:

  1. Provide swimmers and spectators the same air temperature from the same HVAC system;
  2. Use two separate HVAC systems to supply each respective section its most ideal temperature;
  3. Use separate HVAC systems that provide two supply air temperatures, and cordon off the spectator section from the pool area with glass.
Natatorium dehumidification system
Spectator comfort was improved by installing a dedicated dehumidification system.

The first method is the least expensive, most commonly used 25 years ago, and the system originally used at the CAC. The third method is the least desirable, because in the process of separating the two environments, it also mutes the spectators from a swim meet’s exciting atmosphere. Therefore, the CAC design team selected the second option.

The facility’s original mechanical room location, under the spectator area, housed the two HVAC units that performed the dehumidification, cooling, and heating for the entire natatorium. Already crowded with pool equipment, there was not enough space to install two new systems to control two separate indoor environments. Instead, the design team used the original mechanical room to install the unit that would manage the spectator area, and built a new, ground-level mechanical room to house the system for the pool area.

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