Study of Florida Panhandle may foster more sophisticated windborne-debris requirements

July 12, 2006
COMMERCIAL, RETAIL

The results of a recent study could lead to statewide and eventually national adoption of windborne-debris requirements in building codes that factor in terrain as well as wind speeds.

The Florida Building Commission voted June 19 to implement tougher interim windborne-debris codes for the Florida Panhandle and ordered further study of the effect of terrain on windborne-debris damage, says Larry Twisdale, senior vice president from Applied Research Associates Inc. of Albuquerque.

ARA, in conjunction with Florida State University, Tallahassee, completed an in-depth study of windborne debris damage from Hurricanes Charley and Ivan. Hurricane Charley hit Florida’s Gulf Coast in August 2004, and Hurricane Ivan caused extensive damage to the far western end of the Florida Panhandle in September 2004.

Through wind-tunnel tests and risk-assessment modeling, ARA presented at the June 19 meeting a two-phase recommendation to the Florida Building Commission, Twisdale says. The commission accepted both recommendations at the meeting.

Phase I adds interim requirements that call for windborne-debris protection, such as impact-resistant glass or shutters, in areas within 1,500 feet of the coast or where design wind speeds are 130 miles per hour or greater. Current Panhandle building codes require such protection in all areas within a mile of the Gulf Coast.

In Phase II, ARA will continue research on the effect of terrain on windborne-debris damage and “make a statewide recommendation. We’d like to make a national standard that take terrain into account,” Twisdale says.

The initial study measured the cost-benefit ratio of using windborne-debris protection in heavily treed terrain, medium-treed terrains like that in many suburban areas, and open areas such as those around lakes or in prairies.

“The study showed that the effect of terrain was important and that tree terrain was much less likely to have favorable cost-benefit perimeters to justify the need for protection,” Twisdale says.

Richard Dixon, executive director of the Florida Building Commission, says the interim requirements outlined in Phase I could go into effect at the start of 2007. The additional terrain study called for in Phase II should be completed by June 2007, with a building code amendment possibly implemented in mid-2008.