Building design also affects efficiency
There are many ways to efficiently operate an aquatic facility based on the dehumidification equipment chosen and its features. However, even the best equipment will perform poorly if the facility is designed incorrectly and/or has inadequate air distribution.
Basic building design considerations should include protection against air migration. Vapour barriers should be installed immediately behind the interior wall surface to prevent moisture within the pool room from migrating into the wall, where it will quickly reach dew point due to the colder air temperature. If vapour barriers are not installed or installed incorrectly, the dew point will be reached within the wall and the moisture will impregnate the insulation, decreasing its R-value (efficiency).
Thermal performance doors and windows, which limit heat migration and condensation formation, are also important to the facility’s design. For instance, glass doors and windows exposed to outside air should use double- and triple-glass panels and be insulated or sealed in metal or vinyl clad frames. Window frames must have thermal breaks, be sealed to adjacent walls and insulated with a non-porous insulating material.
Pool facilities with open sunlit atriums and windowed walls are candidates for high cooling loads. Increasing ventilation rates during peak periods or simply opening doors and windows can offset this greenhouse effect.
Water attractions such as slides, fountains and water cannons have gained popularity, but higher costs are associated with their operation due to an increase in water evaporation rate. Thus, dehumidification systems must work harder and longer to maintain a desired 50 to 60 per cent relative humidity within the facility.
Surface areas that collect water from the pool also create an additional load on dehumidification equipment. Avoid the use of absorbent deck coverings (e.g. carpet) within the pool area, and limit wet deck areas by installing adequate drainage and/or reducing deck over spray.
Proper airflow maintains comfort, reduces cost
Efficient dehumidification will take place if the air distribution system is designed properly. The air distribution system’s purpose within an aquatic facility is to maximize air flow by keeping warm, dry, supply air over any surface prone to condensing temperatures, including all walls, windows and skylights.
Careful consideration must be given to supply air ducts and air return grill locations. Supply air should be directed at the walls (80 per cent) and along the ceiling (20 per cent) to break up any stratification and stagnation occurring near the ceiling. Using a wall washing technique will also reduce the possibility of cool, dead air spaces forming around windows or walls and migrating to the pool edge. For example, ceiling ducts should be positioned near windows and close enough to sufficiently wash the cold glass with an even blanket of air. The supply air should be ducted below grade around the enclosure’s inside perimeter using linear slot diffusers for low set windows and sliding glass doors. Returns must be positioned so all moist, warm air flows efficiently back to the dehumidification system, eliminating dead areas where air stagnation can occur.
Although typical return heights are located 3 to 4.5 m (10 to 15 ft) above the floor to capture rising warm, moist air, recent studies show positioning returns closer to the pool water surface lightly draws off the chloramine air layer that may settle over the pool’s surface. This technique also draws away moist air while not affecting the evaporation rate or creating uncomfortable air currents.
Ducts should never be positioned in a way that will result in supply air short cycling (recycle prematurely). This can happen when the return duct’s location is too close to, or directly in line with the supply duct.
Maintaining a slight 1.2 to 3.8-mm (0.05 to 0.15-in.) negative water pressure in the pool area, relative to surrounding spaces, will help prevent moisture and chlorine odours from being pushed into other areas of the aquatic facility.
Conclusion
Whether replacing an existing air quality control system or designing a new pool facility, it is important to know a comfortable bathing environment can be achieved without draining the bank through high operating costs. Today’s high-efficiency dehumidification equipment provides benefits for both the facility and the environment. Keep in mind, however, not all equipment is designed and built the same. When dealing with the unique environment of an aquatic facility, be sure to choose a manufacturer with experience in this area to ensure the equipment will offer uninterrupted operation for many years.
Chris Soh is the product manager for Poolpak Technologies Corp., a manufacturer of dehumidification equipment for aquatic facilities in York, Pa. Soh has a bachelor degree in electrical engineering from University of Kentucky. He can be reached via e-mail at sales@poolpak.com.
