Indoor waterpark resorts receive raves for bringing wet fun — and serious dollars — in during winter and cooler months. But come summertime, families tend to look for outdoor activities. Who wants to go into an enclosed space when it’s a beautiful summer day?

With the cost of traditional building systems approaching $500 per square foot, many developers of indoor waterpark resorts are asking themselves the same question. More and more of them are turning to retractable roofing for the answer. Along with natural light, abundant windows and an open-air atmosphere when the weather is warmer, retractable roofs offer good ventilation and breezes. It’s nearly the equivalent of a being outside on a nice day.

However, these roofs have some drawbacks. They can cause heat loss and higher energy costs, depending on the location. And they are subject to many building codes that may conflict with its original manufacturing. Here’s a look at the ins and outs of retractable roofing and how to decide if it’s an option for your resort.

An open concept
Indoor waterpark resorts can be extremely challenging to design, not to mention operate and maintain. This is because the addition of swimming pools, water slides and wet-play elements add humidity and chemical vapors into the building environment. As more play features aerosolize water into the air, building conditions deteriorate faster than in the past.

In years past, many indoor pool facilities incorporated heating, ventilation (air changes), air conditioning and dehumidification to provide patron comfort. But as spray features, squirting and splashing continue in such facilities, indoor air quality becomes a more prominent issue. As a result, these mechanical systems — and the building and finishes designed to mitigate humidity and chemical vapors — have driven the cost of these structures, well, through the roof.

That’s where pre-engineered building structures with retractable roofs come in. This is especially true in areas with temperate year-round climates, though some facilities have been developed in places such as Niagara Falls, Ontario, Canada, and Reno, Nev.

Most of these systems are specifically manufactured with building components and finishes such as aluminum frames and polycarbonate panels (in lieu of traditional glazing) because they’re designed to resist humidity and chemical vapors. A retractable roofing system typically provides a series of operable panels that, in the case of a traditional gable roof profile, slide away from the peak of the roof on blue-sky days. The panels can be moved all at once or one at a time to provide for varying degrees of natural ventilation. If used in concert with operable wall panels at the building perimeter, opening a combination of roof and wall panels can create a natural “flue” effect within the building, thereby allowing a modern-day version of “out with the bad air, in with the good.”

As mentioned previously, the cost of these systems is considerably less than traditional construction methods. The bid cost in December 2004 for one California-area project with a retractable roofing system came in at approximately $1.8 million for 31,000 square feet of roof area. That’s $1 million less than pool enclosure systems using insulated roof panel systems, and $5 million to $7 million less than standard buildings.

In consideration
Many of the pre-engineered, retractable roofing systems have a major drawback, though. When compared with traditional building systems, their thermal performance is somewhat less than stellar.

In California, for example, the state building code mandates an insulating value for buildings of R-19 for roofs and R-11 for walls. Most of the standard option retractable roofing systems can achieve an insulating value in the range of R-5 to R-10, far less than that required by most building codes.

As a result, a significant amount of heat can escape during cold winter months, and conditioned air can be released in summer.

For this reason, potential resort developers should consult with their design teams and local building departments to ensure that this type of system can be approved in their areas. Manufacturers of retractable roofing systems can be helpful, providing case studies and examples of where and how their systems were approved in other areas.

What this means is that the use of retractable roofing systems should be carefully considered in regions where large swings in outdoor air temperature are prevalent. These systems can be more attractive to waterpark resort developers in the Southwest and Southeast, for example, than in the Midwest and Northeast due to the more temperate weather.

Other favorable weather considerations for retractable roofing include wind and fog. In Las Vegas, for instance, a number of facilities have adopted the retractable roofing system in recent years because in outdoor conditions, patrons would be “sandblasted” by the wind. Similarly, foggy areas such as the San Francisco Bay Area; Portland, Ore.; and Seattle have seen a number of facilities with retractable roofing systems developed to reduce the overall cost of the building, yet still protect patrons from the influence of foggy or rainy weather.

Code issues
Another hurdle is that prefabricated enclosures can be considered permanent structures, which means they’re subject to local building codes.

Such codes are particularly challenging in California. At one facility, for example, code dictated occupant load calculations based on a ratio involving the pool’s surface area. With this method, the architect calculated 775 occupants, a number that normally would require a certain assembly area occupancy classification, which entails fire rating the structural frame. However, the manufacturer’s aluminum frame system did not lend itself to this type of treatment. Using an exception spelled out in California’s building code, the architect prepared and gained approval of an occupant load management plan and added exit doors to his design. By doing so, he attained a different occupancy classification for the enclosure that does not require a fire-rated structural frame.

Yet another roadblock revolves around fire safety. For example, an enclosure may have double-layer polycarbonate roof panels at a C-level fire safety rating, but based on occupancy class, a Class B roof rating is required. In one case, satisfying this requirement meant limiting the use of polycarbonate to no more than 33 percent of the roof area. The manufacturer designed a three-component roof system using the standard polycarbonate for the operable roof sections, which took up the allowable 33 percent, and fixed insulated glass and metal panels in all other areas. All materials were specified in a blue color to maintain the aesthetic harmony of the roof.

Sprinklers are a third issue. A large enclosure may require a full sprinkler system to be installed. But a building department may rule that areas directly below the operable roof don’t need sprinklers because the retractable portions of the roof are situated over pool areas, according to California code. Moreover, installing sprinkler heads in the operable roof area defies common sense because whenever the roof is open, the heat bank necessary to activate them in case of a fire would not be available.

Given traditional building construction costs, retractable roofing systems can be aesthetically pleasing and cost-effective alternatives for indoor waterpark resorts. These systems allow the patron to experience the best of both worlds: protection from the elements when the weather is less than perfect, and all the glories a sunny day in the pool can offer.

Just make sure that you fully examine the feasibility with designers and building officials prior to incorporating a retractable roof or pre-engineered building system into your project.