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ARA Study Shows How to Keep the Roof On and Insurance Costs Low

May 2011

Hurricane House Damage

ARA analysis of hurricane-force winds and their effect on structures, especially homes, reached another milestone as the IntraRisk Group recently demonstrated how much hurricane wind speeds can vary between the coast and inland communities. This work could potentially lead to lower insurance costs and ultimately help revitalize New Orleans.

In a study funded by the New Orleans Redevelopment Authority (NORA), ARA engineers and scientists simulated hurricane wind speeds in New Orleans and found them to be about 10 percent less than winds along the coastline.  This is critical information for NORA and the Louisiana Insurance Commission, since wind storm insurance can account for nearly two-thirds of a homeowner's insurance costs in New Orleans. By demonstrating the lower wind speeds, and thus a lower risk of wind damage to homes, this research provides another tool to help provide sound data on which to base insurance rates, which went up 500 percent after Katrina, and potentially save homeowners in the region millions of dollars annually through lower premiums.

Another part of the study focused on hurricane resistance assessments of actual homes in the city. In a survey of 542 homes, ARA showed that homes could be mitigated to withstand wind damage and reduce losses. This effort built upon an ARA study from 2002 and revised in 2008, that was the first-ever industry study to quantify the effects of wind-resistive features, including windborne debris protection, on the reduction of losses to single family houses caused by hurricanes. That study, originally funded by the Florida Department of Community Affairs (DCA), set the standard for the computation of insurance credits. That DCA-funded study for single family houses was expanded to include multifamily dwellings later, and in 2008 the updated study included new features not included in the first study such as new roof slopes, number of stories, roof tiles, metal roofs and soffit failures. ARA has performed wind tunnel tests on single family homes to improve the understanding of wind loads on buildings located in forested areas. ARA also developed loss relativities for Florida Building Code wood panel shutters applied to both wood frame and masonry structures.

ARA's IntraRisk Group has been performing research services similar to that performed for the NORA study for more than 11 years (since 2000), with the development of a first principles based model for estimating hurricane induced windborne debris impact criteria for use in developing design standards. Specifically, this work provides people living in a hurricane-prone area a detailed understanding of how to make their homes more secure during a hurricane. The intent is to encourage homeowners to take steps to mitigate their wind risk by retrofitting their homes to reduce the risk of hurricane damage, making them more safe and secure. ARA is currently pursuing this type of study in other Gulf Coast states to provide their residents with the same sort of detailed understanding of the risks they face and the steps they can take to prepare for hurricanes.

IntraRisk employees performed all of the work on this study from the division's Raleigh, N.C., office and a former satellite office in Tampa, Fla. Dr. Larry Twisdale led the work and was supported by Dr. Peter Vickery, Jeff Sciaudone, Dr. Frank Lavelle, Dr. Tony Rigato and Dr. Bo Yu. 

For more information on this and other work from ARA's IntraRisk Group, contact William Ratliff at wratliff@ara.com.