“To put it bluntly, air handling in the waterpark has been one of the biggest challenges since the evolution of the whole indoor water park phase,” says Schmitz, aquatic director of the Great Lakes Co., the Madison, Wis., firm that owns the Great Wolf Lodge resort brand.

That’s because all the splashing and spraying at an indoor waterpark adds tremendously to the normal evaporation — excess moisture that can ruin a facility and cause health problems.

This is where dehumidifiers come in. Just as facilities have become more sophisticated, so have dehumidification systems. Beyond simply removing excess water vapor, some models even recycle energy, which can be put to use heating water or air. Others incorporate new technology that “scrubs” the air while dehumidifying. Of course, no system is perfect. But experts say understanding how they work and which type you need is crucial for today’s waterpark resorts.

The old way
In the past, operators addressed the humidity issue by bringing in outside air, heating it, blowing it across the facility and out the other end of the building. The advantage, says Alison Osinski, Ph.D., owner of Aquatic Consulting Services in San Diego, was that the system is healthy. After all, it whisks the heaver-than-air gasses sitting over the pool out of the building.

But even in the best of weather, this approach is far from ideal: It increases evaporation, chills swimmers whenever the air hits their wet skin and creates excessive noise from the blowers.

High humidity also causes health problems. Industry statistics show that the incidence of rhinitis and asthma increases at below 40 percent and above 60 percent relative humidity. Fungi and mites increase at above 60 percent RH, as do chemical interactions. Ozone products increase at below 40 percent RH. The casual swimmer who comes in for an hour or the lap swimmer who goes all out for 20 minutes won’t notice any effects, she adds, but people who work in that environment commonly develop respiratory difficulties.

The new way
Today’s dehumidifiers were born when heating, ventilation and air conditioning (HVAC) engineers put their heads together to solve air problems for indoor pools. However, it’s more complicated than flipping a switch. For instance, operators must know about something called the dew point, the temperature at which water condenses in their facilities.

If it’s above 50 degrees, consultants recommend what is known as DX dehumidification. This system cools the air that comes from the pool and, in the process, picks up the latent (or sensible) energy to put into the refrigerant. Next, the system adds the heat of compression, which in this case is the electrical energy coming from the plug in the outlet, to the refrigerant. At this point, you have a hot gas containing energy — energy that you can use for many applications: to reheat the air that comes from the cold coil, heat the space or heat the pool water. In other words, you control that energy, diverting it to areas where you need it most. Costs for DX systems range from $30,000 to $200,000 depending on the size of the facility.

If your dew point falls below 40 degrees, desiccant dehumidification provides the best solution. In this system, a turning wheel impregnated with desiccant material absorbs moisture. Once it collects the moisture, the wheel then turns so that it’s in a stream of super-heated air (approximately 250 degrees). That air dries out the wheel so it can again collect moisture. The energy recovery savings, however, can’t stand up to DX, say manufacturers, though costs are comparable.

Manufacturers also have begun chatting up a new option: gas-phase filtration. The science is built on using scrubber beds of activated charcoal filters to absorb specific pollutants. Thanks to their higher bather loads, waterpark resorts make the ideal clients for this twist.

Among the early problems these engineers have flagged: Retrofit applications add load to the fans, so pool operators will need to either add horsepower or purchase a booster fan. But the good news is that gas-phase filtration can stand alone; it doesn’t depend on a dehumidification system at all to perform its air-cleaning function.

Fresh air
But no matter how high-tech — or low-tech — your system is, it still must be augmented with fresh air. Without that ingredient, you could trade high energy bills for health costs.

“The best advice I have for my colleagues is that this is not a substitute for fresh air,” says Gerald Rappaport, general manager of the Hilton Milwaukee City Center, which features an indoor waterpark.

Commercial indoor pools codes may specify 15 percent fresh air, but Osinski suggests nothing less than 40 percent. Ideally, you should completely turn over the air 10 complete times per hour. The system also should move the air from low to high for a cross-ventilation effect and with enough velocity to move it, but not so much it chills the swimmers.

So how do these new systems work? While nothing is perfect, operators who are using them wouldn’t go back, for the most part.

Just ask Schmitz. One of his facilities, Blue Harbor Resort in Sheboygan, Wis., sprang for a fancy dehumidifier model from Europe. To date, he’s had no complaints and, in fact, plans to install a second unit at a resort in the Pocono Mountains.

Rappaport’s engineering crew underestimated how much outside air would be needed to handle the 61,200 gallons of water housed in 20,000 square feet of fountains. But he’s satisfied that it’s keeping the humidity at crowd-pleasing levels.

“And we’re getting some additional preheating for our water from it,” he says. “It just comes down to [the fact that] dehumidification is a vital piece of the puzzle.”

About the author
Julie Sturgeon is a freelance writer
based in Greenwood, Ind.