The easy answer to why you should use a pool dehumidifier is so your pool building doesn’t fall down. There are several other answers relating to the operation and performance of the dehumidifier, such as economically maintaining temperature and humidity comfort of the room envelope for your clients and staff, but you must prevent the building materials from degrading.
Indoor pool rooms are expensive to build, operate and maintain. Think of it as a cardboard box filled with water. Pool rooms are maintained at very high moisture levels, and the moisture inside the pool room is trying to get out through the walls and ceiling throughout the year. The architects and mechanical professionals design the pool room differently than any other building structure. There has to be a significant vapor barrier on the inside wall of the structure.
Natatorium facilities evaporate many gallons of moisture into the air of the pool room each hour. This moisture is very corrosive due to the disinfectants used to keep the water clean and acceptable to the patrons, and meet required health codes. The American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) also provides recommendations for temperatures and moisture levels within the pool room.
The codes require delivering outside air ventilation rates to maintain acceptable indoor air quality, and to exhaust pool room air to maintain a negative pressure. This is required to prevent pool room odors from permeating into other areas of the building.
The pool room’s air temperature is held at a consistent temperature — approximately 2 degrees above the pool water temperature. This is to reduce the water evaporation rate and minimize the dehumidifier size. Maintaining these conditions allows the owner to minimize utility costs, as dehumidifiers are specifically designed to remove moisture from the room air, as well as outside air when necessary.
The dehumidifier’s supply air is heated and typically will maintain the constant pool room temperature required. The materials of the building determine the required minimum dewpoint of the supply air. One cannot put moist air on a cold surface, as this will create condensation on the walls, windows and doors of the pool room. All these surfaces must have their temperature maintained above space dewpoint to prevent condensation.
As a point of information, typical air conditioning units are rated by their energy efficiency ratio (EER), which is the heat removed divided by the amount of energy used to remove this heat. Pool dehumidifiers are rated in moisture removal efficiency (MRE), which is the amount of pounds of moisture removed, divided by the amount of energy used to remove this moisture.