Twenty years ago, humidity control for an indoor swimming pool was to bring in outside air while pushing the warm humid air outside with large exhaust fans. This process only worked effectively when the outside air temperature was cool and dry enough to allow for humidity control. This type of system is not only ineffective, but it is the most expensive to operate in a pool enclosure because it cannot consistently maintain the required 50-60% RH humidity levels. When compared to conventional ventilation or "waste ventilation" systems, recycling and dehumidifying pool enclosure air with a mechanical dehumidifier can save 50-75% on energy costs, maintain the 50-60% RH required by ASHRAE, and provide 100% room heating, air conditioning and pool heating.
Preventing condensation is perhaps the most important purpose of all for dehumidifying an indoor pool enclosure. If condensation forms in or on wood, plaster, or other porous materials, it can cause warping, rot, mold, mildew, rust or simply saturate the material until it loses its integrity.
At Veri-Dry, we believe a successful project starts with good design. The objective for designing mechanical air handling systems for pools is to ensure that no surface within the pool enclosure or within the structural members of the building will reach "Dew Point" and cause moisture to condense. The DXair Dehumidifier helps to accomplish this objective by reducing the relative humidity in the pool enclosure and therefore, effectively reducing the Dew Point Temperature.
Sizing of all dehumidification systems is based on the basic following information. It is important to understand the geographics and demographics for your design temperatures/conditions. Warmer climates will have a greater cooling load, especially if bringing in large amount of Outside Air. Colder climates will have a higher heating load. It is also important to understand the building materials required for maximum protection and prevention of condensation.
Q. Why is a dehumidification system necessary to control humidity in an indoor pool/natatorium?
A. Indoor pools and spas, due to the nature of containing a large body of water, have a much higher humidity level than any other area of commercial or residential buildings. As this moisture reaches a 100% humidity saturation level within the pool room, humidity and moisture — if not controlled — are destructive to dry wall, wood, metal, insulation, interior structural members, and equipment. Additionally, this can foster an uncomfortable and unhealthy environment for all. A properly designed indoor pool dehumidification system will prevent the early deterioration of the structure by reducing the pool room humidity levels to the standards required by ASHRAE. While dehumidifying the indoor pool room environment, the system will also provide the necessary heating, cooling and additional free heat resources to the natatorium.
#1: "It's Just Another Room"
Quite often, pool room dehumidification systems are an "afterthought". Structures are completed without consideration for controlling humidity, ductwork systems, vapor barrier, negative pressure, and mechanical space to name a few. The cost of preventing problems in the design stage is much less than the repair costs down the road.
The Design Guidelines are in PDF format, are printable and can be shared with all involved in your project. This information has been gathered over the years from a variety of resources, building professionals, pool contractors, architects, engineers, mechanical contractors, ASHRAE, ACCA, and is not expressly the opinion of Veri-Dry, LLC. Providing of these guidelines does not negate your own research into building materials and preventive measures for your indoor pools; they are provided as an additional resource to ongoing research.