Swimming Pool HVAC Design Considerations
By Chris Schoonover, PE, LEED AP, BCxP
The recent cold weather in Northeast Ohio has served as a reminder that maintaining environmental conditions in wet, humid pool buildings can be very challenging. Entire books have been devoted to the topic. The following are some of the primary concepts to keep in mind when planning, designing and operating pool systems.
Like any other building system, an agreement on what design parameters should be utilized must be reached. Due to the close integration of the systems in a pool, this is even more vital than usual. Pool designs will be very dependent on obvious specifications, such as quantity/quality of glazing, room air temperature, and humidity ranges. Less obvious factors that affect the performance of the aquatics area include the pool temperature(s) and activity levels, quantity of spectators, and adjacency to other “dry” spaces in the building. Pressure relationships are especially problematic in a mixed climate, such as Ohio. The recommendation is to keep pools slightly negative to other spaces. But, care must be taken at doors leading directly outside, since too much infiltration can lead to condensation or moisture. While the surface finishes in the pool area should be able to withstand and drain moisture, condensation can result in nuisance drips, staining or corrosion, and should be avoided.
Careful coordination of the pool envelope, including glazing systems and vapor/moisture barriers, is a must for a successful aquatics center. Proper installation by the trade contractors is just as important. High performance glazing and mullion systems with no through-metal are a must. A well-sealed and continuous vapor barrier should be part of the building envelope. This is typically installed on the warmer side of the assembly. Attention to how support spaces and pool equipment rooms relate to each other are also helpful in insuring the pool HVAC system air is not being mixed with zones supported by conventional systems. This will improve energy performance, as well as lengthen the life of the building. All building materials that may be wetted, including the HVAC system components, need to be selected with anti-corrosive characteristics. Be aware that stainless steel products may not always offer rust resistance, depending on their exact grade and application. Verify with accessory manufacturers whether they will warrant their products in a pool or aquatics environment.
Pool HVAC systems have more sophisticated controls systems since they monitor and regulate moisture as well as temperature. These systems frequently have cooling and energy recovery cycles operating during a much higher number of hours each year. If not thoroughly tested and commissioned, these systems may consume more energy than desired, or possibly even fail to meet the design criteria. Major unresolved control issues of installed and occupied pool HVAC systems with may include:
• Compressors locked out to save energy, resulting in no dehumidification
• No program for dehumidification
• Heat recovery cycles not operable
• Outside air dampers inoperable or not capable of economizing
• Pool units disabled during unoccupied hours
A complete commissioning of the pool HVAC systems can assist with helping to define parameters. More importantly, it insures adequate dialogue amongst trade contractors and validation of proper operation prior to occupancy. The cost to engage commissioning can be a fraction of the cost associated with a poorly performing building.
This outlines just a few of the common pitfalls one can encounter with pool design and operation. It is not intended to be a definitive design guide. ASHRAE handbooks offer good starting resources for design parameters, as do pool HVAC equipment manufacturer application guides. Questions or concerns about a pool facility are best directed to an experienced architect or HVAC engineer.