And, yes, we did say this is a huge indoor waterpark that just so happens to be located smack dab in the Midwest’s winter cold. Temperature-wise in Wisconsin Dells, the average high in December is 29°F, with an average low of 11°. In January, the average high is only 25°, with the average low a chilling 4°. In February, the average high is 31°, while the average low is 9°.

Just the presence of hundreds of thousands of gallons of water splashed around with wave machines, water cannons, water slides, and patrons can create rainforest-like conditions. Combine that with airborne byproducts of such a facility’s necessary pool water sanitizing chemicals and IAQ becomes vital for patron comfort. Take in that outside cold, too, and you have yourself an even tougher challenge.

But despite these IAQ challenges, the Wild Waterdome is a breath of fresh air in Wisconsin Dells, which proclaims to be the world capital of waterparks with over 20 facilities.

TRUSTING, USING FABIC DUCT

Established in 1928, Kilgust Mechanical is one of Madison’s largest full service design-build mechanical contractors.

 

In regard to the Wild Waterdome, the finished mechanical task could be seen as a testimony for fabric ductwork, which did play one of the important roles in the creation of good IAQ. Jason Beren, P.E., vice president of operations, designed the airflow around six 120-foot long runs of 60 inch and 66 inch diameter TufTex premium-grade fabric duct from DuctSox (Dubuque, Iowa). This included a variety of orifice diameters ranging from 3/4-inch to 1 1/2-inch and various duct circumference placements. The two perimeter runs positioned 19 feet above the floor have two linear arrays of orifices directed toward the windows and another array toward the deck.

Typically indoor waterparks use coated spiral metal duct with relatively few large diffusers to direct enough air movement toward the windows to reduce condensation. In the eyes of Beren, this design is acceptable for industrial situations; however, in occupied spaces, the higher-velocity drafts may be uncomfortable for patrons, especially where wet body surfaces can easily be chilled by drafts.

Working with the engineering department of DuctSox, Beren agreed to use fabric duct, as this allowed the designers to select the throw, direction, and volume of airflow per section. According to Beren, this allowed a target airflow of 75 to 100 feet per minute (fpm) at the pool deck level.

In this project, Beren explained that the thousands of orifices engineered into the fabric duct meet the needs of the structure, while providing a gentle airflow to occupants. The even distribution also helps eliminate air stratification in the far corners of the space, which is a problem in larger spaces, he said. The computer-aided-design (CAD) orifice placements also help evenly draw airflow off the Wild Waterdome’s unique Texlon Transparent Roof System.

These intricate ventilation rates were fine-tuned and confirmed during Kilgust’s design process with the aid of a computational fluid dynamics (CFD) analysis. Matthew Herman, building physicist, Buro Happold Consulting Engineers, based in New York, performed the CFD work. “Fabric duct resulted in a huge HVAC savings, but equally important was the fact the fast-track project’s ductwork installation time was cut nearly in half,” said Beren.

IT'S PRETTY, TOO

From an architectural standpoint, Architectural Design Consultants Inc. (ADCI) admits that the streamlined fabric surface - that’s void of typical ribbing and protruding registers - offers an aesthetic alternative to spiral metal ductwork. And that is coming from a successful hotel, resort, and waterpark design firm, which has nearly 20 years of experience in the field.

 

“With no prior fabric duct experience, we were a bit skeptical in the beginning,” confessed Raymond E. Bolton, AIA, principal at ADCI, which is based in Lake Delton, Wis. “But we’re really pleased how it performs and looks, especially the custom earth tone color that coordinates with the rest of the space. It’s designed to resist corrosion, so it’s really a good choice for this type of space.”

Additionally, the Wilderness took advantage of DuctSox’s new silk screening program. With dozens of competing restaurants in the Wisconsin Dells area, the Wilderness subliminally directs patrons to its own restaurant facilities with silk-screened logos of each venue appearing on the duct-work surface that’s in full view of all Wild WaterDome patrons.

The mechanical side of Kilgust’s design is based on a total 220,000-cfm capacity produced by four ventilation units from XeteX Inc. (Minneapolis, Minn.). According to the design-build contractor, there’s no dehumidification as in typical natatoriums, but rather a reliance more on outside air supply and exhaust with four to six air changes per hour, depending upon the season.

According to the Wilderness staff, summer operation features 100 percent untreated outside air and rapid air changes. Large natural ventilation openings, such as oversized doors, windows, and louvers, were incorporated to reduce energy consumption in the summer ventilation mode. According to the operators of the Wilderness, this method, combined with good air distribution, helps reduce chloramines accumulation.

In wintertime operation, the XeteX units are designed to transfer the heat from warm exhaust air and use it to preheat the incoming cold, outside air. If return air heat recovery isn’t sufficient, the units’ direct-fired burners are designed to heat it to temperature setpoints. Meanwhile, the huge solar gain the facility receives from its glass roof also aids the wintertime space heating effort, said Wilderness officials.

Last, but certainly not least, variable-frequency drives by ABB (New Berlin, Wis.) add to the system’s flexibility and energy efficiency.

The bottom line is this: As waterpark design evolves in the 21st century, design-build companies have - and will - become leaders in mechanical design innovations. Kilgust Mechanical, for one, is a believer in fabric duct and its unique airflow capabilities. One could even say it is a design-build trend.

Publication date: 01/08/2006