Competition and exercise pool spaces are more likely to be maintained at temperatures around 82°F (28°C), or lower. This is driven by the recommendation (2003 ASHRAE Handbook— HVAC Applications, pp. 4.6 – 4.8) to keep the air temperature about 2°F (1°C) above the water temperature to help reduce evaporation from the pool and improve the comfort of bathers exiting the pool. This will be discussed later.

Although residential space conditions can vary, it is important for the designer to convince the pool owner not to maintain the space conditions at normal comfort levels because somepeople want to use their indoor pools as places to have parties. If abnormal natatorium conditions are required, the designer needs to know what the real conditions will be for proper dehumidification equipment selection. Since no one wants to swim in 73°F (23°C) water, the pool evaporation rate will increase dramatically as a result of the increased vapor pressure differentialbetween the warmer pool water and the colder air.