Wind codes shape our future

Doors and Hardware, June, 2007 by Kurt Roeper

IN THE YEARS SINCE 1992, WHEN HURRICANE ANDREW CAUSED $21.6 BILLION of insured damage to Florida and Louisiana, severe storm wind codes have gone from being practically non-existent to being the threshold of inclusion within the International Building Code (IBC), thus moving from obscurity to national recognition.

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Even as Andrew's damage was being rebuilt, officials in South Florida, led by Miami-Dade County, promulgated test protocols tailored to the dynamics of hurricanes, specifically covering cyclic wind forces and impact resistance. Previously, the legacy model building codes had focused primarily on straight-line wind loading with no specific provisions for resistance to hurricane debris impact. As the aftermath of Andrew was further studied, prevention of the devastating chain-reaction effects of windborne debris became a priority. Incorporating these new test protocols and standards into the South Florida Building Code represented a first step in addressing the potential for severe wind damage and requiring the design of structures to resist these forces of nature.

The need was, and remains, critical. According to the National Center for Atmospheric Research, tornadoes and hurricanes cause average annual property damage of $6.2 billion. Of this amount, hurricanes are responsible for $5.1 billion in damage and 20 deaths per year, while tornadoes cause $1.1 billion in damage annually.

As the potential for damage, death and destruction from hurricanes received increasing attention, further developments occurred in the area of wind-rated openings and resistant construction. In 1998 the Florida Legislature created the Florida Building Commission, charged with drafting a statewide building code to harmonize the needs of the entire state. As a result, the Florida Building Code was published in 2001 with design standards similar to those pioneered by the South Florida Building Code, with the creation of the High Velocity Hurricane Zones for Miami-Dade and Broward County

At the same time, losses from tornado damage were being addressed with the introduction of standards such as FEMA 320 and FEMA 361, which cover the construction of tornado shelters. FEMA 320, Taking Shelter from the Storm, is a prescriptive guideline for the construction of residential storm shelters, while FEMA 361 is a blend of prescriptive and performance-based guidelines for community shelters. Further information is available at the FEMA website, www.fema.gov.

While each of these individual documents provided some minimum level of prescriptive or performance criteria, there was no model code providing consistency across jurisdictions. Now these developments are coming together at the national level, with the formation by the International Code Council (ICC) of a Consensus Committee, which has written and submitted for public comment a document that will govern the construction of residential and public tornado and hurricane shelters. Because the ICC encompasses both commercial and residential construction virtually nationwide, this development promises to raise the level of awareness and performance on this issue to greater prominence.

As the commentary process moves forward, it brings us closer to including provisions in the ICC's International Building Code that reflect the requirements for construction able to withstand severe wind forces. Once published, such provisions will be available for adoption by the many states, municipalities and governing bodies throughout the country, as appropriate for their local conditions.

The impact promises to be widespread. Although hurricanes and tornados are often thought of as regional in nature, 50 percent of the US population now lives within 50 miles of the coastline, and every state without exception has been struck by at least one tornado. As the US population continues the migration toward coastal areas, the potential for significant losses due to storms increases, as does the need for qualified shelter space.

The losses from such storms are staggering. The Insurance Information Institute reports that the estimated insured loss from the top 10 hurricanes between 1992 and 2005 totaled more than $111 billion in 2005 dollars (See Figure 1). Loss of life is also significant. During the period from 1986 through early 2006, tornadoes resulted in 1065 deaths (See Figure 2).

Shortage of Emergency Shelter Space Drives Demand

As major storms continue to dominate the news many times each year, the need to improve protection for people and property drives an increasing demand for products that can cope with the damaging forces generated by these storms.

While awareness of the potential for damage from severe windstorms is on the increase, there remains a shortage of qualified shelter space, which is still acute in some areas. A study published recently by the Florida Department of Community Affairs, available at: http://floridadisaster.org/bpr/Response/engineers/2006sesp.htm indicates that progress is being made there, but much still needs to be done (See Figure 3). According to the report, Florida reduced its shelter deficit by almost 75 percent between the years 2000 and 2006, but the state still faces a shortfall of more than 400,000 general population spaces. The study projects that, if the current rate of shelter space production is maintained, the state's public hurricane shelter deficit will be eliminated by 2010. However, as Florida's population increases every year and some designated shelters are decommissioned because of age or better alternatives, a "maintenance level" of space production will have to be continued to avoid a deficit in the future. Similar situations exist in other parts of the country, many of which are not nearly as far along in developing the shelter space they require. This promises to fuel a continuing demand for qualified openings that meet the emerging wind code requirements.