Rounding out a two-part series, RTM Principal Doug Brewer shares his expertise on natatoriums, frequently referred to as indoor swimming pools. In the first post, Brewer shared the complexities of natatoriums and outlined the importance of preventing condensation and achieving desirable indoor air quality. In the second installment Brewer highlights the importance of creating optimum temperatures, equally vital for a successful facility.
Creating optimum temperatures
Temperature and humidity go hand-in-hand, playing a critical role in human comfort. It is essential that both are controlled and stable. The space temperature in a natatorium is unique to each project, but typically ranges between 75 and 85 degrees F. Optimum relative humidity levels range between 40% and 60%. While 40% is certainly an acceptable indoor relative humidity level, most indoor pools do not operate lower than 50% rH due to significantly increased utility costs; increased pool water evaporation rate resulting in more make-up water and water treatment; and swimmers leaving the water feel chilly at lower humidity levels due to evaporation off their bodies.
While the space temperature should be dictated by the owner based on what satisfies the users, it is important to understand the resulting energy consumption. For example, at the same water temperature, a pool in a room at 78 degrees F and 50% rH will evaporate almost 35% more than that same pool in an 85-degree F room at 50% rH. Every pound of moisture evaporated to the space is a load to be dehumidified, and it also represents heat lost by the pool water. Pool water evaporation losses account for 90% of a pool’s annual water heating cost. Every pound of moisture evaporated represents approximately 1000 Btu of heat.
While each natatorium will need to accommodate specific design requirements stipulated by the owner, preventing condensation, achieving desirable indoor air quality, and creating optimum temperatures play an imperative role when providing a safe, healthy, comfortable and energy-efficient pool environment.