When designing an indoor swimming pool, it must be understood that the room – the natatorium – is a unique space, which will require a number of special design considerations. First of all, the natatorium is a special room containing a large volume of water that must be continually heated, chemically treated and cleaned 24 hours a day. It is, therefore, unlike most public spaces, which can be closed down at night and given little attention until the next day.
Because of the pool, very high humidity will develop in the room. The humidity generated can have a negative effect on ferrous metals, certain types of composition board and building material finishes. Humidity can also affect such materials in adjacent spaces, areas into which high levels of chlorine-laced, damp air migrates from the natatorium.
To avoid these inherent problems, the educated designer is advised to:
- Reduce the relative humidity level in the natatorium to 50-60 percent.
- Create a negative air pressure, which will be maintained in the natatorium relative to the adjacent spaces.
- Specify building materials, components and finishes that will not be affected by moisture, humidity and/or chlorine vapors and its by-products.
These performance specifications can be achieved in a number of ways. The most direct is to:
- Provide a dehumidification system that will monitor the relative humidity in the space, dehumidify the air, reheat it to several degrees below the ambient air temperature and drain off the condensate. Such equipment is available in the marketplace as package units, or a system can be built from engineered components.
- Create barriers between the natatorium and adjacent spaces with air locks or at least doorways that will isolate the pool area from other spaces such as locker rooms, weight rooms, running tracks, aerobic exercise studios and, most important, administration offices and lobbies.
- Select building materials that will not be affected by humidity or chlorine and its by-products. Such materials are glass, tile, stainless steel, epoxy-coated structural steel, concrete and concrete masonry units.
- Create necessary thermal barriers when the natatorium has common walls and ceiling with the outside temperature.
Acoustics are a problem for any natatorium, because the previously-listed structural and finish components often exacerbate the inevitable noise surrounding a swimming pool. Special CMUs, sound baffles and ceiling treatments that are compatible with high humidity levels all can help deaden sound.
The air temperature in a natatorium should be maintained at approximately 2 degrees higher than the water temperature. While competitive swimmers – including master swimmers – will prefer a water temperature of 78-80 degrees, most fitness lap swimmers will desire a slightly warmer temperature.
Indoor swimming pools often have the stigma of being cold with barren walls, a chlorine smell and reverberating echoes. None of this is necessary today. As mentioned before, acoustics can be emphasized. Automatic water quality controllers will eliminate the chlorine smell, and a more thought-out choice of warm materials and colors will add to the atmosphere of the space, especially if plants are made a part of the interior design.