Spray polyurethane foam (SPF) has been around for decades, and its insulating value is well documented. What’s less well known is the value of SPF in hurricane zones. Recent studies, such as one commissioned by the Spray Polyurethane Foam Alliance in 2007, have shown that SPF-insulated walls and roofing resist missile damage and penetration as well as high winds. Due to its continuous surface, it also protects against water intrusion.
Rick Tucker, global business manager for Honeywell’s TerraStrong closed-cell spray foam, says commercial contractors typically use SPF for roof systems. “It can also be in the walls if it’s a steel-stud type building, or sprayed onto a masonry wall with a façade, such as brick, in front of it,” says Tucker.
Mason Knowles, a Savannah, Ga.-based consultant to the SPF industry who specializes in education and training, has researched the effects of hurricanes on the product. “In the last 10 years, and specifically the last five or six years with the violent hurricanes that hit Florida, the structural benefits of spray foam have been more quantified,” says Knowles. In a 2008 study conducted at the University of Florida and sponsored by Honeywell and Huntsman, SPF was applied to the underside of roof decks built for high-velocity wind areas. Wind uplift resistance (the ability of a roof surface to withstand the upward force of air pressure below it) doubled for picture-frame assemblies and even tripled for three-inch-fill assemblies.
The racking strength of spray foam has also been demonstrated, according to Knowles. Racking strength is the measure of a wall system’s ability to resist wind loads. “The strength of wall assemblies increased anywhere from 50% on up to 200%, depending on the type of sheathing used,” he says. The Roofing Industry Committee on Weather Issues (RICOWI), a nonprofit research and education corporation associated with Oak Ridge (Tenn.) National Laboratory, has measured the performance of roofing systems after hurricanes and found that spray foam installed inside and outside minimizes damage from hurricane-strength winds. Honeywell’s Tucker notes that closed-cell SPF also serves as a moisture, thermal and air barrier due to its seamless, monolithic composition.