Building a house on a sweet spot near the coast is a commission most architects covet. But when Hurricane Andrew slammed into South Florida, on Aug. 24, 1992, it made some reconsider the opportunity. “The biggest part of the problem [during Andrew] was the openings in the building envelope,” says Brian G. Warkentin, product development manager for Loewen in Steinbach, Canada. “Flying debris broke windows and wind rushed in and ripped off the roofs.”
The most destructive United States hurricane on record, Andrew caused some $26 billion worth of damage and exposed serious flaws in Florida's building standards. As a result, South Florida developed what are perhaps the nation's most stringent building codes: This High-Velocity Hurricane Zone stipulates that exterior openings must withstand 140-mph-plus winds, so houses must either be protected with shutters or windows and doors with impact-resistant glass. Subsequently, windows and doors sold here must be large missile– or small missile–certified.
code solvers Other jurisdictions have followed South Florida's lead. Over on Florida's west coast, construction codes also have changed—most noticeably for window requirements. “It's the biggest change we have experienced,” architect Donald Cooper, principal of Cooper Johnson Smith, says.
Along the North and South Carolina coast—where architects must design with 130- to 140-mph wind speeds in mind—the same trends are gaining ground. “I feel like we have been designing houses the way we always have, but the window openings have been getting smaller and smaller,” says Tyler Smyth, an architect with Christopher Rose Architects in Johns Island, S.C.
Christopher Rose Architects prefers to use impact-resistant glass, but if the budget is tight, the codes allow regular glass if the home is equipped with enough plywood to cover each window. That provision will soon disappear, however, leaving architects with two options: impact glass or shutters.
Code changes have reached as far as eastern Long Island, where the wind zone is a more lenient 120 miles per hour. Like other jurisdictions, the codes allow architects to build a house as “fully enclosed” or “partially enclosed,” says Frederick Stelle, principal of Stelle Architects in Bridgehampton, N.Y. “With a partially enclosed house, an architect must design so that if the windows blow out, the house will stay intact,” he says. An enclosed building must be designed to resist a breach of the envelope, which includes using impact-resistant glass or shutters.
New Jersey recently adopted the International Code Council's strict standards for wind resistance, structural loads, and windows and doors. “There are now some limits on us,” says Michael Ryan, principal of Loveladies, N.J.–based Michael Ryan Architects. “We design based on the availability of products and what the systems allow.” Ryan, who prefers Andersen for its breadth of products, says the codes discourage custom doors. “It is difficult to do now because code officials are looking for products that already have been certified.” Every custom product, on the other hand, would require time-consuming testing.
Most architects agree that code changes have altered the way they design their houses. Cooper says it used to be difficult to find certain windows and doors that met requirements. “We could not get double-hung windows, so we had to switch to casements,” he says. Smyth says his firm still can't always find the right products.
Fortunately, impact-resistant windows and doors are easier to locate these days and are available in greater variety. Most manufacturers have lines designed for high-wind areas. Loewen's StormForce comes in three levels of protection from simple missile–impact to products with Dade County approval. St. Paul, Minn.–based Marvin says its StormPlus is certified for high pressure, impact resistance, and energy efficiency.
LifeGuard is a specially engineered upgrade line in Medford, Wis.–based Weather Shield's Legacy Series. Available in casement, tilt double-hung, and direct set windows and French doors, LifeGuard products pass the coastal codes in Florida and other Southeast states.
You can still have large glass openings along the coast. Mill Valley, Calif.–based NanaWalls says its popular folding framed system now comes in a version that is Dade County–approved. “The SL72 meets air, water, forced entry, structural, impact, and pressure cycle requirements,” says president Ebrahim Nana. “An architect can have glass openings up to 36 feet.”
Bayport, Minn.–based Andersen Windows says its Stormwatch products allow architects to ditch the shutters and plywood sheets. “People want protection year-round,” says Mark Mikkelson, manager of code, regulatory and technical marketing. “You don't have to put up shutters.” Stormwatch products have frame, sash, and panel reinforcements, upgraded hinges, and structural silicone glazing. About 75 percent of Andersen's standard line is available with Stormwatch.
strong thinking Designing a house in a high-wind zone isn't solely about specing impact-resistant windows, however. “There are a lot of things to think about,” says Timothy J. McNamara, town architect at the vacation home community of Rosemary Beach, Fla. “Some things are code-driven, some are dollar-driven, and others are about peace of mind.”
Architects must consider design pressure criteria, water penetration, and the ramifications of a partially enclosed versus a fully enclosed structure. A partially enclosed structure requires exhaustive and costly construction, McNamara says. An enclosed structure, however, requires impact-resistant windows and doors, which can cost three times more than standard products.
“It is getting tougher for architects to design in these areas,” says Loewen's Brian G. Warkentin. “There is so much more that they have to know. Some architects over-design when they don't need it, and the customer ends up buying a lot more window than is necessary.”
To help architects determine the minimum code requirements for their jurisdiction, Andersen launched the Design Pressure Estimator and Coastal Products finder. The Web-based tool allows architects to enter certain site information such as wind speed, exposure, building category, and mean roof height, and the estimator generates the overall design pressure requirements. The product finder can also recommend Andersen products that meet the design needs. “The Estimator is fairly accurate, but the data should still be verified by a code body,” Mikkelson says.
No matter which state, building in a vulnerable area is a pricey proposition. Codes now require architects to use cross bracings and tie-downs to make houses more hurricane resistant. In South Carolina, which also has a seismic requirement, codes force architects to drive concrete piles 50 and 60 feet down, adding significantly to foundation cost, Smyth says. But Cooper says this is a good thing, and it pays off in the end. Code changes did not affect his firm significantly, he says. “We believed they were good construction practices, so we had been doing them already.”