Air-supported vs. frame-supported
Fabric sports field structures have become popular as teams seek ways to extend their practice opportunities during less than ideal weather conditions. The objective is a wide, long and high covering with no columns or supports to obstruct the playing area, yet with greater flexibility and lower costs than traditional, permanent building construction.
The two types of systems most frequently selected for this purpose are air-supported fabric "bubbles" and frame-supported, fabric-covered structures. These can be installed or constructed in a much shorter time, and the foundation requirements are less than those of a traditional building. Frame-supported structures cost an average of $40 to $60 per square foot and can generally be built in 120 to 180 days. In comparison, air-supported structures run $5 to $20 per square foot on average, and can be built within 90 to 120 days. Air-supported structures also offer the benefit of portability.
Air-supported structures use internal, pressurized air to inflate, and support, structural fabric. The internal pressure must meet or exceed external pressure, such as wind, in order to maintain structural integrity. Inflated structures are equipped with either two sets of doors or a revolving door to create an airlock. Air-supported structures require only a small amount of pressure to remain inflated: approximately .036 PSI.
The structures are available in a variety of configurations and can also be custom-designed. Ron Scharf, chairman of Arizon Companies (www.arizoncompanies.com), said his company offers a variety of sports field layouts, including multiple tennis courts, soccer fields, football fields and a multisport field surrounded by a track. The structures can also be manufactured with transparent fabric, eliminating the need for lighting during the day. "That’s a huge savings when you’re talking about a 50,000-square-foot area," Scharf said.
Often, the inflation and climatic control equipment is put in place at the time of the installation of the synthetic turf surface the bubble will cover. When the bubble is added to an existing facility, those elements are included in the installation process. When all external components are in place, the installation has been described as similar to setting up an air mattress; the material is rolled out over the area to be covered. If multiple sections are involved, these are connected with an airtight seal, and the bubble is inflated. The fabric is covered with "netting" to preserve the shape. Scharf said Arizon uses stainless steel airplane cable for this application.
Wind resistance and snow load capabilities are issues to consider, with needs depending on what area of the country you’re in, but systems can be designed to adjust to climatic conditions. "Our machinery automatically detects wind and snow and increases the pressure inside," Scharf said. "In snow, it sends warm air through the fabric to melt the snow."
Warranties vary, so check the supplier’s projected life of the structure.
Frame-supported, fabric-covered structures allow year-round play for parks and recreation programs, community sports centers and high schools, as well as university and professional level teams.
Though most suppliers of these products have standard components for construction in stock, they understand that the unique needs of each facility may best be met with a customized design. "Let the ideas flow," said Simone Clayton, senior marketing manager for Cover-All
Building Systems (www.coverall.net), based in Saskatoon, Saskatchewan. "The design team of our Summit Structures division can combine all the client’s needs and ideas into a digital format that gives them a visual of the concept structure. They can work from that to add or delete to create the custom design with all the interior features they choose to include. Our steel-framed engineered fabric structures can span up to 300 feet in width and even greater in length."
There are multiple differences within the basic components of these systems, so do your homework. Examine the suppliers’ warranty to assess whether the anticipated longevity of the structure meets your needs. Some suppliers use a steel frame, others use aluminum. The type and weight of the fabric/membrane covering varies, and it can be translucent or opaque, with some products available in a choice of colors.
The width of the structure can range from 20 to 500 feet. Height options vary, as do the shape and slope of the roof. Length offers almost unlimited flexibility, with most products providing the option to add to the structure if additional space is needed.
While most of the frame-supported structures remain in place year-round, others are designed as modules that can be taken apart and moved to storage or reconfigured for different uses.
Compare overall operational costs to those of permanent structures and the options within the frame-supported category. Energy costs will be a factor if the structure will be temperature controlled. Look into insulation options and how they would impact long-term operational costs. Check with suppliers about the anticipated operational costs for their products, and ask users of those structures how their costs compare to those figures.
The author is a contributing editor for SportsField Management. Editor Katie Meyers contributed to this article.