Natatorium HVAC Design: 4 Factors to Help Ensure a Safe and Sustainable Project
Aquatics centers require an experienced team to design solutions to ensure occupant safety
Natatorium HVAC (heating, ventilation, and air conditioning) design requirements are stringent for a very good reason. If the HVAC design and equipment installation are done by an inexperienced team, a natatorium could be at risk for a higher level of health and safety issues, causing problems for occupants and the facility itself.
So, how do you avoid running into potential issues? There are four main HVAC factors to consider when designing natatoriums. At the beginning of each project, experienced mechanical engineers will focus on the following areas and develop solutions for each:
- Temperature and humidity controls
- Pressurization control
- Air distribution
- Ventilation rates
In other building projects, if these factors are not controlled, the risks are less serious. However, if these items are not properly addressed in a natatorium, a facility can sustain serious long-term damage and cause occupant health and safety issues.
Through our experience working on projects like the Scheels Aim High Big Sky Aquatic and Recreation Center, and the MSU Wellness Center we address these four areas of HVAC design, ultimately benefiting the performance and the outcome of both new and upgraded natatoriums.
Temperature and Humidity Controls
The relationship between water temperature and surrounding air conditions plays a critical role in HVAC system design. As water temperature increases, the vapor pressure at the surface rises, increasing the vapor pressure differential between the water and the surrounding air. This accelerates evaporation and increases the amount of moisture introduced into the space, which must be accounted for in the system’s latent load. Significant evaporation is also caused by features such as kids’ play zones with spraying water features, bucket drops, and wave pools. Understanding how these features affect the HVAC system is key to designing solutions that meet the needs of the facility’s temperature and humidity controls.
Natatoriums must maintain a relative humidity (RH) between 50% and 60% to meet indoor air humidity standards. The higher the air temperature, the lower the evaporation rate; however, temperatures need to be limited to 84°F to maintain occupant comfort levels.
Pressurization Control
Natatoriums are very humid; therefore, it’s imperative to maintain a negative pressure relative to adjacent spaces and the outdoors. This critically important function keeps the moisture out of the walls and the roof and is especially important in cold climates like Montana, Idaho, Oregon, Washington, and Wyoming , where it can hit subzero temperatures for several days. The differential in dry-bulb temperature and relative humidity between the space conditions (84°F and 60% RH) and the outside conditions (-10°F and 20% RH) means that moisture, if not controlled, will drive into exterior walls and/or the roof at a significant rate.
Pressure control, along with strategic vapor barriers and proper insulation values, prevents warm, humid air from penetrating into the building’s materials where it would otherwise condense and develop mold growth and rot. It is recommended that natatoriums be designed with a variable-speed exhaust fan to control pressure (relative to adjacent spaces) between -0.15 and -0.05 in. w.c. It is entirely possible to achieve strict pressure control via this variable-speed exhaust strategy and a space differential pressure sensor within the natatorium.
Air Distribution
Air distribution systems in natatoriums play a critical role in controlling condensation on surfaces that fall below the dew point. An effective distribution strategy is essential to mitigate several common issues. Exterior windows, for example, naturally drop below the dew point and require a constant supply of air to maintain surface temperatures above it. Similarly, thermal bridges between exterior and interior elements of the building should be eliminated as much as possible, since condensation will form on any bridging components.
Proper airflow across the pool surface is also important; moving air at a slow velocity helps remove chemical-laden air and improves air quality in the breathing zone. However, if air velocity is too fast, it can increase evaporation rates and lead to occupant discomfort. An effective strategy to remove this air is to implement exhaust intakes as close to the surface as possible. This can be achieved with dual-purpose bench evacuators or air evacuation built into the deck drain itself.
Once the air distribution strategy is fully developed it can be analyzed through computational fluid dynamics (CFD) software to ensure air speeds are sufficient and low temperature surfaces are being effectively washed by the HVAC supply air.
Ventilation Rates
Keep in mind that humid natatorium air can cause several health-related issues. For example, the water evaporated at the pool surface contains volatile organic compounds (VOCs). VOCs can cause headaches and dizziness in the short term, while long-term exposure can lead to respiratory issues. VOCs are especially pronounced within 18” of the water or where swimmers are breathing and relaxing in the pool. Proper and precise control over the ventilation rates is important to occupant health in natatoriums.
Ventilation rates are determined by accounting for the total pool area, the 5 ft area outside of the pool (the wet deck), and the remaining area (the dry deck). The pool and the wet deck must be ventilated at a rate of 0.48 CFM per sq. ft., while the dry deck may be ventilated at 0.06 CFM per sq. ft. Spectators also need to be accounted for in competition pools, resulting in an increase in ventilation by 7.5 CFM per person.
Natatorium Services
Designing HVAC systems for natatoriums and aquatic centers is a unique skill set that requires an elevated level of understanding of design, equipment selection, and installation. We have created several structural, mechanical, electrical, and plumbing designs for a wide range of projects, each unique, but all needing the same level of safety and performance.
If you’re facing a new project, reach out and let’s talk. We’re always happy to talk about a solution that works for you.
Learn more about our aquatic center projectsAbout The Authors
With a decade of experience in mechanical engineering, Sam Kuhlin designs systems that provide high-quality air and temperature-regulated spaces to work, live, and play.
Learn more about Sam
As the Buildings Market Group Leader, Tom Coburn works collaboratively with his team to identify unique and creative approaches to solving his clients' complex problems.
Learn more about TomRelated Projects
Montana State Student Wellness Center
Montana State University’s new Student Wellness Center co-locates health, counseling, recreation, and exercise-related academic programs into a single, student-centered facility.
Scheels Aim High Big Sky Aquatic and Recreation Center
Morrison-Maierle provided MEP, ICT, and fire protection system designs for the Scheels Aim High Big Sky Aquatic and Recreation Center in Great Falls, Montana.
Bobcat Athletic Complex
The Bobcat Athletic Complex is a 40,000 sq. ft. facility next to Montana State University's football stadium that supports the university's athletes and coaching staff.