The presence of water within an enclosed space results in high humidity conditions. To dissipate the humid air from the enclosed space one can incorporate a ventilation fan which will continually remove the humid air from the space without it being able to accumulate to very high humidity levels. When air is vented out of the space, fresh air will displace this air. During winter months this air will be very cold and uncomfortable unless it is preheated. The other alternative is to incorporate a dehumidifier that condenses the moisture onto a cold evaporator coil (just like the droplets that form on a soft-drink when taken out of the refrigerator). This process of drying the air (dehumidification) is very energy efficient because the energy absorbed in the process of converting the humid air into a liquid is captured by the heat transfer on the evaporator (cold coil) surface and transported by the refrigerant to the hot cold where the process air is reheated.
Refrigeration type dehumidifiers are more effective for hot and humid conditions typically associated with indoor swimming pools. Some indoor swimming pools are heated for further comfort when swimming and this increases the rate of evaporation from the surface of the swimming pool substantially and necessitates the use of more powerful dehumidifiers to cope with the added moisture load.
The hot and humid air inside the pool area condenses on cold surfaces causing moisture droplets and mould. Where there are glass surfaces, these mist up as a result of the fine droplets. Walls inside pool areas will absorb moisture unless they are suitably treated to function as vapour barriers. Other problems that arise include:
- Rust occurs on all metallic fittings
- Electronic devices & equipment within the space have premature failure associated with corrosion
- Floor surfaces can be slippery (puddles) as a consequence of water droplets falling from the ceiling
- Damp problems occur in the rest of the house as a result of water vapour spreading
Because indoor swimming pools are constantly generating large amounts of water vapour, it is strongly advised that the indoor swimming pool space be isolated from the rest of the house in order to minimize the water vapour from spreading to other areas.
Many indoor swimming pools are not properly engineered. A well designed indoor pool area will have provision for the following:
- Vapour sealed and thermally insulated walls and windows
- Air ducts blow air over glass windows to minimize condensation
- Use of stainless steel or non-corrosive materials inside the space
- Containment of the humid air to the pool area only (i.e. fully enclosed)
- Adequate electrical power supply for dehumidifier within close proximity to the swimming pool room
- Adequate space for dehumidifier
The following factors all contribute towards the sizing of the appropriate dehumidifier for the application:
- Water surface area of the swimming pool
- Water temperature
- Indoor room temperature
- Minimum outdoor air temperature
- Activity (splashing, swimming, pool usafe factor)
- Air movement over the surface of the pool